Sensorineural Function (Eye Anatomy) PDF

**SENSORINEURAL FUNCTION.** **[Overview of Anatomy and physiology of the eye.]** The eyeball or globe is situated in the bony structure known as the Orbit. The eye is the organ of the sense of sight and it is supplied by optic nerve (2^nd^ cranial nerve). The space between the eye and the orbital...

**SENSORINEURAL FUNCTION.** **[Overview of Anatomy and physiology of the eye.]** The eyeball or globe is situated in the bony structure known as the Orbit. The eye is the organ of the sense of sight and it is supplied by optic nerve (2^nd^ cranial nerve). The space between the eye and the orbital cavity is occupied by adipose tissue. The bony walls of the orbit and the fat help to protect the eye from injury. There are three layers of tissue in the walls of the eye viz: The outer fibrous layer: Sclera and Cornea; the middle vascular layer or uveal tract: Choroid ciliary body and iris; the inner nervous tissue layer:- retina. Structures inside the eyeball are the lens, aqueous fluid (humour) and vitreous body (humour). The orbit is about 4cm high, wide and deep; and it is shaped roughly like a four sided pyramid surrounded on three sides by the sinuses: ethmoid (medially) frontal (superiorly) and maxillary (inferiorly). At the optic foramen, optic nerve and artery enter the orbit. Movement of the eyeball is possible through extra ocular muscles -- 4 rectus muscles, (superior, Inferior, lateral and medial) and 2 Oblique muscles (superior and inferior). These muscles are innervated by cranial nerves III IV and VI. **Eyelids**:- They are two movable folds of tissue situated above and below the front of the eye. They have short curved hairs on their free edges called eyelashes. The layers of tissue that form the eyelids are a thin covering of skin, thin sheet of loose tissue, two muscles -- orbicularis oculi and levator palpebrae superiors, lining conjunctiva. The eyelids contain multiple glands including sebaceous, sweat, and accessory lacrimal glands. With every blink of the eyes, the lids wash the cornea and conjunctiva with tears which are formed by the lacrimal gland and the accessory lacrimal glands. Healthy tear is composed of three layers; lipoid, aqueous and mucoid. Tears are secreted in response to emotional or reflex stimuli. **Conjunctiva**:- It is a fine transparent membrane that lines the eyelids and the front of the eyeball. Where it lines the eyelids, it consists of highly vascular columnar epithelium. It protects the delicate corneal and the front of the eye. The globlet cells of the conjunctiva secrete lubricating mucous. **Sclera and Cornea:-** The Sclera or the white of the eye forms the outermost layer of tissue of the posterior and lateral aspects of the eyeball and is continuous anteriorly with the transparent cornea. The Sclera consists of a firm fibrous membrane that maintains the shape of the eye and gives attachment to the extra-ocular or extrinsic muscles of the eye (which is the 4 rectus & 2 oblique muscles). Anteriorly the sclera continues as a clear transparent epithelial membrane, the cornea. Light rays pass through the cornea to reach the retina. The cornea is convex anteriorly and is involved in refracting or bending light rays to focus them on the retina. The conjunctiva meets the cornea at the [limbus] on the outermost edge of the iris. **Interior of the Eye:-** The anterior segment of the eye i.e the space between cornea and the lens is incompletely divided into anterior and posterior chambers by the Iris. The chambers contain a clear aqueous fluid (humour) secreted into the posterior chamber by the ciliary glands. It circulates in front of the lens through the pupil into the anterior chamber and returns to the venous circulation through the sclera venous sinus (canal of schlemn) in the angle between the Iris and the cornea. There is continuous production and drainage, and the normal intraocular pressure (10P) is 10 to 21mmHg. An increase in this pressure causes glaucoma. **Uvea**:- It consists the Iris, ciliary body and choroid. The iris which is the coloured part of the eye is a highly vascularized, pigmented collection of fibres surrounding the pupil which dilates and constricts in response to light. The dilation and constrictions are controlled by sphincter and dilator pupilae muscles and these muscles are controlled by parasympathetic and sympathetic nervous system respectively. Behind the iris and the pupil is the lens which is a highly elastic circular biconvex body and it is suspended from the ciliary body by the suspensory ligament. The lens enables focusing for near vision and refocusing for distance vision. Its thickness is controlled by the ciliary body by the suspensory ligament. It is the only structure of the eye that can vary its refractory power. When the ciliary muscle contacts, it moves forward, pulls the lens and increases its thickness. The nearer the object being viewed the thicker the lens. Ability to focus and refocus is called accommodation. The aqueous humour is anterior to the lens and vitreous humour fills the posterior segment of lens. The vitreous humour is a jelly like, soft, colourless and transparent substance composed of 99% of water, some salts and micro-protein. It maintains sufficient intraocular pressure to support the retina against choroid and prevent the walls of the eyeball from collapsing. The shape of the eye is kept because of the intraocular pressure exerts by the vitreous body and aqueous fluid. Choroid:- This lines the posterior five-sixth of the inner part of the sclera. It is rich in blood vessels. Light enters the eye via pupil, stimulates the nerve ending in the retina and is then absorbed by the choroid. **Retina**:- This is the innermost layer of the wall of the eye. It lines three-quater of the eyeball. It is stimulated by rays of light. It is composed of several layers of nerve cells bodies. It is thickest at the back and thins out anteriorly to end just behind the ciliary body. Macula lutea is situated near the centre of the posterior part. Retina consists of cone and rod shaped cells that contain photosensitive pigments that convert light rays into nerve impulses. Retina vessels enter the through the optic nerve, branching out through the retina and forming the superior and inferior arcades. The area of retina responsible of central vision is the macula. The rest of the retina is responsible for peripheral vision. In the centre of the macula is the most sensitive area, the fovea (which is a vascular) and it is surrounded by the superior and inferior vascular. Retinal pigment epithelium (RPE) and the sensory retina are the two important layers of the retina. A single layer of cells is made up of RPE and one of the functions of these cells is to absorb light. The sensory retina contains the photoreceptor cells called Rods and Cones. Rods and cones are long, narrow cells shaped like rods and cones. Rods are for night vision or vision in low light while cones provide the best vision for bright light, colour vision and the detail. Cones are found throughout the retina and have more in the fovea. Rods are absent in the fovea. Healthy functioning eyeball and intact visual pathway makes good visual acuity. The pathway is made up of retina, optic nerve, optic chiasm, optic tracks, lateral geniculate bodies, optic radiations and the visual cortex area of the brain. The second cranial nerve which is the optic nerve helps to transmit impulses from the retina to the visual area in the occipital lobe of the brain. Optic nerve head or optic disc is the physiologic blind spot in each eye. The optic nerves from the two eyes as they leave the eye meet at the optic chiasm (a point at which the nasal fibers for nasal retina of each eye cross to the opposite side of the brain). The nerve fibers from temporal retina of each eye remain uncrossed. Fibers from the right half of each eye which is the left visual field carry impulses to the right occipital lobe. Fibers from the left half of each eye which is the right visual field carry impulses to the left occipital lobe. The fibers are known as **optic tract** when they pass beyondthe optic chiasm. Optic tract continues to the lateral geniculate body (in the thalamus) which leads to the optic radiation and then to the cortex of occipital lobe of the brain. **See the diagram of human eye below** **[Physiologyof vision.]** Light rays entering the eye are bent (refracted) as they pass the curved surface of the cornea and through the various structures of the eye (aqueous humour) to focus on the retina. The cornea provides the major refractive change for light entering the eye, with the lens providing the fine focus for light transmitted posteriorly to the retina. The eye can adjust (accommodation) to viewing objects at various distances by flattening or thickening of the lens. Near vision requires contraction of the ciliary muscles in the ciliary body. This contraction allows the ciliary muscle to move forward and relaxes the zonule attached to the lens. The lens bulge to bend the light rays so that the rays focus on the retina. Accommodation is also facilitated by changing the size of the pupil. The iris constricts the pupil in the near vision to force light rays to pass through the shortened but thicker than lens. The pupils also constrict when the light is bright to protect the retina from intense stimulation. Light rays are absorbed by photoreceptors on the retina, change to electrical activity and transmitted through the optic nerve which divided at the optic chiasma (Chiasm), the medial portion of each nerve crosses to the opposite side to form [optic tract] and the impulses are transmitted through the lateral geniculate body of the thalamus. There will be optic radiation from this body and these are transmitted to the visual area in the occipital lobe of the cerebral cortex visual information received by the each eye is transmitted simultaneously to both sides of the brain. Bilateral vision provides depth perception. See diagram below N B:- The light passes via the conjunctiva, cornea, aqueous fluid, lens and vitreous body. All rays entering the eye are refracted (bent) to focus on the retina. Light rays eye cornea pupil lens retina optic nerve optic chiasma optic tract lateral geniculate body optic radiations visual area in cortex. **[Physiological changes with Aging.]** Aging affects many aspects of visual function, both physiologic and anatomic. There is decrease flexibility and elasticity of the lens and this is one of the first noted signs of aging -- the decrease ability of the eye to focus (accommodate) for near and detailed work (presbyopia). With aging colour vision declines and this contributes to impaired depth perception. This causes more difficulty in differentiating among colours. A smaller pupil (senile miosis) adds to this distortion in colour, it also affects the amount of light that reaches the peripheral retina and the ability of the person to adapt to dim light and darkness. As a result of this older person has impaired night vision. **[Extrinsic Muscles and their functions.]** Superior rectus -- Rotates the eye upward and toward the nose. Inferior rectus -- Rotates the eye downward and toward the nose. Lateral rectus -- moves eye toward the temporal side. Medial rectus -- Moves eye toward the nose. Inferior Oblique -- Rotates eye upward and toward the temporal side. Superior oblique -- Rotates eye downward and toward the temporal side.. **[Assessment.]** -Subjective Data. A complete visual assessment consists of a careful patient interview combined with physical assessment of the eye structures. Health history is important before diagnosis is made. General areas explored during the interview include the patient's assessment of his/her vision and any recent changes in visual acuity, whether glasses are used. Health history should include age, occupation and lifestyle, family history, past health e.g history of hypertension, Diabetic Mellitus, Renal disease, hyperthyroidism, brain injury or tumour. -\`Objective Data:- Observe the tissues of the eye because abnormalities are easily detected. Basic assessment of the eye:- \- Facial and ocular expression:- Prominence of eyes, alert or dull expression. \- Eyelids and conjunctiva:- symmetry, edematous, itching, redness, discharges, blinking, equality, growths. \- Lacrimal system:- Tears, swelling, growths. \- Sclera:- colour. Papillary reflex:- - Light:- Constriction of pupil in response to light in that eye (direct light reaction), equal amount of constriction in the other eye. - Accommodation:- Convergence of eyes and constriction of pupil as gaze shifts from far to near object. - Peripheral vision:- Ability to see movement and objects well on both sides of field of vision. - Acuity with and without glasses:- Ability to read newsprint, clocks on wall. - Supportive aids:- Glasses, contact lenses prosthesis. [Assessment of vision.] Vision acuity means acuteness or sharpness vision and this indicates measurement of distance or near vision. Distance vision:- This is determined by the use of a Snellen Chart. With a person standing 20 feet (6m) from the chart. The chart consists of rows of letters, numbers or other characters arrange with the larger ones at the top and the smaller ones at the bottom. The uppermost letter on the chart is scaled so that it can be read by the normal eye at 200 feet and successful rows are scaled so that they can be read at 100, 70, 50, 40, 30, 20, 15, 10 feet respectively. Visual acuity is expressed as a fraction and a reading of ^20^/~20~ is considered normal. Each eye is tested separately using a piece of cardboard to cover the eye not being tested. Near vision:- This can be tested with the use of newsprint or Jaeger Chart which contains various sizes of print that is held about 14 inches (35cm) from the eye. **Visual Acuity Measurement** ^20^/~20~ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Normal ^20^/~40\ --\ 2~ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ missed two letters of the ^20^/~40~ line. ^10^/~400~ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ At 10ft, reads line that normal can see at 400ft. ^CF^/~2ft~ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ count fingers at 2 feet. ^Hm^/~3ft~ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ see movement of hand at 3 ft. NLP \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ No light perception. Anyone with less than ^20^/~30~ OD (right eye) or OS left eye should be referred to ophthalmologist. The External Eye Examination. External eye examination is performed after the visual acuity has been taken and recorded. The position of the eyelids is noted. The upper 2mm of the iris are covered by the upper lid. The patient is examined for ptosis (drooping eyelid due to paralysis of the 3^rd^ cranial nerve) and for lid retraction (leading to exposure of too much of the eye). The lid margins and lashes should have no oedema, erythema or lesions. Inspect the sclera (normal sclera should be opaque and white). Note lesion on the conjunctiva, discharge and tearing. The pupils should be examined in a dark room. Use penlight to check for reaction of the pupil. Normal pupil is black. An irregular pupil might be due to trauma, previous surgery or a disease process. The eyes are inspected for primary or direct gaze and any head tilt is observed. Examiner observe for nystagmus (an involuntary, rapid movement of the eyeball which may be hereditary or result from disease of semi-circular canal. Extraocular movement of the eyes is tested by having the patient follow examiner's fingers or pencil. **Diagnostic Evaluation** Laboratory and smears of corneal or conjunctiva swab and scrapings in the diagnosis of infections. A sample of exudates is obtained. - Direct and Indirect Ophthalmoscopy The fundus of the eye is examined with a hand-held instrument called an ophthalmoscope which magnifies the view of the back of the eye so that the optic nerve, retina, blood vessels and macula can be seen through the pupil. The examiner may use direct or indirect method of ophthamoscopic examination. The indirect ophthalmoscope allows the examiner to view the retina allowing a wide-angle view. This indirect method is performed by ophthalmologist. Direct method is easily to perform. The entire retina cannot be visualized at one time, the examiner moves the ophthalmoscope until the entire fundus is visualized. With the instrument held on the right hand by the examiner, the right eye can be visualized and vise-versa. The room should be darkened and the examiner's eye should be at the same level with that of the patient. **Slit-lamp Examination** The slit-lamp is a binocular microscope mounted on a table. It is an instrument that combines a microscope and a light source. By adjusting the lens, the examiner can test for problems such as ulceration, lens changes, foreign bodies in the vitreous or retinal changes. **Colour Vision Testing** This is used to test for colour blindness in persons seeking motor vehicle license or jobs for which colour discrimination is important. Colour vision deficiencies occur as a hereditary defect in both men (7%) and women 0.5%. Nutritional deficiencies, drug toxicity and various disorders of the optic nerve and fovea centralist can alter colour perception. **Amsler Grid:** This is a test often used for patients with macular problems such as macular degeneration. **Tonometry:** Tonometry measures intraocular pressure by determining the amount of force necessary to indent or flatten a small anterior area of the globe of the eye. The instrument used is called tonometer. The test is used to detect early glaucoma. Other test include Ultrasonography, fluorescein angiography, Goniscopy, perimetry testing **[Low Vision:]** This is the visual impairment that requires patients to use devices and strategies in addition to correlative lenses to perform visual tasks. Low vision is best defined as a best corrected visual acuity (BCVA) of ^20^/~70~ to ^20^/~200~. **Assessment** This includes thorough history and examination of distance and near vision acuity. **History:** This should include the cause and duration of the patient's visual impairment: Patient's customary activities of daily living; medication regimen, habits e.g smoking; acceptance of the physical limitations brought about by the visual impairment. **Evaluation:** Contrast -- sensitivity testing measures visual activity in different degrees of contrast. The test may initially take the form of simply turning on the lights while testing the distance acuity. Glare testing enables the examiner to obtain a more realistic evaluation of the patients ability to function in his/her environment. Glare can reduce the patient's ability to see (especially in patient with cataract. Management-- To manage low vision, it involves the use of low vision aids and strategies. The goals are to enhance visual function and to help patient to perform normal activities optical devices including convex lens aids such as magnifiers and spectacles, telescopic devices, anti-reflective lenses that reduces glare and electronic reading devices such as closed circuit television and computer with large print. **[Blindness:]** This is defined as best corrected visual acuity (BCVA) of 20/400 to no light perception. Blindness is clinically defined as absence of light perception. Legal blindness is when an individual has BCVA that does not exceed ^20^/~200~ in the better eye and the widest visual field diameter is 20 degreesorless. Nursing Management: Coping with blindness requires three types of adaptation viz: Emotional, physical and social. Emotional adjustment to blindness determines the success of the physical and social adjustment. [Promoting Coping Efforts]: Effective coping efforts will only come when the patient has recognized the permanence of his/her blindness. Hanging on to false hopes of regaining vision may affect the coping efforts. The ability to accept changes must come with visual loss and willingness to adapt to those changes influence the successful rehabilitation of the patient who is blind. There is going to be value change i.e from independent to dependence conflicts, coping with stigma. [Promoting spatial orientation and mobility]:-People who are blind rely on egocentric, sequential and positional information that centres on the person and his/her relationship to the objects in the environment. Topographic movement of front, back, left, right below measures of distance help the person to locate objects in relation to person who is blind. The goal of orientation and mobility training is to foster independence in the environment. Training include using mobility device for travelling e.g long cane, dog guides [Promoting home and community-based care]: The nurse social workers, family and others collaborate to assess the patient's home condition. The level of visual acuity and patient preference help to determine appropriate intervention There may be community based programme through medi-care programmes, support services such as vocational Rehabilitation programmes offered by the division of blind services Glaucoma is a condition caused by an elevation in pressure within the eye due to retention of aqueous fluid./Glaucoma is a group of ocular conditions characterised by optic nerve damage which is related to the intra ocular pressure caused by congestion of aqueous humour in the eye. Glaucoma has be in called the ''silent thief of the sight ''because the loss of vision often occurs gradually over a long period of time Glaucoma is one of the leading causes of irreversible blindness. lt is the 2^nd^ leading cause of blindness it is more prevalent among people older than 40years of age. Aqueous fluid is produce by the ciliary body and flows from the posterior chamber into the anterior chamber. From anterior chamber the fluid passes via the iridocorneal angle in to the trabecular meshwork and schlemm's canal and then through the aqueous veins into the venous circulation. The process of production and distribution of aqueous fluid is a continual one and is responsible for maintaining the normal intraocular pressure (10-20mmhg). [Risk factors for Glaucoma] \- Family history of glaucoma \- African -- American race \- Older age \- Diabetes \- Cardiovascular disease \- Migraine syndrome \- Nearsightedness (myopia) \- Eye trauma \- Prolonged use of topical or systemic corticosteroids. [Classification of Glaucoma] There are two types of glaucoma and these are open-angle glaucoma and closed angle glaucoma ( also called angle closure glaucoma) \- [Open angle glaucoma]: This type of glaucoma is also referred to as chronic simple glaucoma and occurs more frequently, tends to progress slowly and patient may not notice they have loss vision unit the disease has progressed significantly. It is characterised as a disordered increased IOP, degeneration of the optic nerve and visual field loss. It makes up of 90% of glaucoma cases. [Closed -angle (Angle-Closure) Glaucoma]: The angle refers to areas between the iris and cornea through which fluid escapes through trabecular meshwork. This is a closure in which an obstruction occurs at the access to the trabecular meshwork and the canal of schlemm. IOP is normal when the anterior chamber angle is open and glaucoma occurs when a significant portion of that angle is closed. [Pathophysiology**:**] The anterior chamber is anatomically shallow in most cases. When there is a mechanical blockage of anterior chamber angle results in accumulation of aqueous humour (fluid). The shallow chamber with narrow angle is more prone to physiologic events that result in closure. Angle closure occurs because of pupillary dilation or forward displacement of the iris. This acute angle closure causes dramatic response with sudden elevation of IOP and permanent eye damage within several hours if not treated. There will be scar tissue form between the iris and cornea. The iris and ciliary body begin to atrophy, the cornea atrophy because of Oedema and the optic nerve begin to atrophy. In open-angle glaucoma (90% of all and the damage as insidious. It could also be more rapidly in response to injury or infection or as a complication of surgery. [Clinical manifestations] \- Pain in and around the eye due to increased IOP. \- Rainbow of colour around lights. \- Vision becomes cloudy and blurred. \- Pupil will be mildly dilated and fix. \- Hazy appearing cornea due to oedema of the cornea. \- Nausea and Vomiting. \- Profuse lacrimation. [Diagnostic Evaluation:] -Tonography Estimation of resistance with outflow channels by continuously recording the IOP for over 2 to 4 minutes. \- Ocular examination - which may reveal a pale optic disk. \- Tonometry measurement of IOP \- Gonioscopy to study the angle of the anterior chamber of the eye. \- Ophthalmoscopy -- evaluation of colour and configuration of the optic cup. [Management ] Medical Management -- The goal of treatment is to lower the individual's IOP and keep it at the level that prevents loss of vision. Emergency Chemotherapy is initiated to decrease eye before surgery. Medication classification include \- Cholinergics drugs e.g pilocarpine,Carbachol:- They contract pupil, draw iris from the cornea, aqueous humour may drain through lymph spaces (meshwork) into canal schlemm. \- Carbonic anhydrase inhibitor e.gAcetazolamide, methazolamide, dorzolamide:- It restricts action of enzyme that produces aqueous humour. \- Beta blockers e.g betaxolol, timolol: -- it decreases production of aqueous humour. \- Alpha Adrenergic agonistse.gbrimonidine, apraclonidine -- it decreases aqueous humour production. \- Hyperosmotic agent -- to reduce IOP by promoting dieresis. [Surgery-] This is indicated when IOP is not maintained within normal limits by medical regimen and there is progressive visual field loss with optic nerve damage. Types of surgery to be done are - Laser Trabeculoplasty, laser iridotomyTrabeculectomy [Nursing Management:] \- Medical and surgical management of glaucoma slows the progression of glaucoma but does not cure it. \- Patient should be relieved of pain. Narcotic drugs must be administered as prescribed. The goal of treatment which aimed at reducing IOP as quickly as possible should be explained to the patient.Reassure patient that with reduction of IOP other symptoms and pain will be reduced. \- Relieving fear: Reassure and calm patient to reduce fear and anxiety. \- Prepare patient for surgery if necessary and describe the procedure/surgery to him/her that after the procedure vision will be blurred for few days. Patch will be worn for several hours and sunglasses. Teach patient how to correctly administer topical eye drops. \- Patient education and Health Maintenance: Instruct patient on the use of medications, follow-up of appointments, patient to seek medical attention if signs & symptoms of increased IOP return -- severe eye pain, photophobia, and excessive lacrimation. [Guidelines for Self administration of Eye drops.] 1\. Wash the hands thoroughly before administering the medication. 2\. Tilt the head back and look up toward the ceiling 3\. Pull the lower eye lid gently down and out to expose the conjunctiva and create a sack. 4\. Bring the dropper from the side and apply the eye drops. Avoid touching the eye lashes, conjunctiva or surface of the eye with the dropper. Resting the thumb on the fore head can help to stabilize the hand. 5\. Close both eyes gently. Do not squeeze them tightly to expel medication. 6\. If more than I drop is to be administered wait for 2-5 minutes before administering the second drop. [Complications of Glaucoma] \- Vision loss \- Blindness A cataract is a lens opacity or cloudiness that leads to gradual painless burning and eventually loss of vision. It is the 3^rd^ leading cause of blindness. It could be unilateral or bilateral. [Classification of cataract] Cataract is generally classified as -[Senile cataracts:] These are associated with aging process and are not preventable. There is some evidence that exposure to ultraviolet radiation may significantly contribute to cataract formation.Speculation exists that antioxidant use such as the combined intake of vitamin A, C and E may reduce the risk of senile cataract, but this is also not proven. -[Traumatic cataracts:] This is associated with injury. It is the next common identifiable cause of cataracts. The transparency of the lens may be destroyed by either a penetrating wound or a contusion. \- Congenital Cataract -- occurs at birth. \- Cataracts may also occur secondary to eye diseases such as uveitis or eye trauma or with system disease such as diabetes mellitus, galactosemia. [Risk Factors] \- Age: the incidence increases dramatically after age 65. There will Loss of transparency, decreased 0xygen uptake, increase in sodium and calcium, decrease in levels of vitamin C, protein. \- Sex: It is common in women \- High dose radiation exposure \- Drug effects: use of corticosteroids. \- Poorly controlled diabetes mellitus; Renal disorders, musculoskeletal disorders, disorders related to lipid metabolism, Down syndrome. \- Poor nutrition \- Obesity \- cigarette smoking \- Retinitis pigmentosa \- Myopia \- Infection such as Herpes zoster, uveitis [Pathophysiology**:** ] Senile cataracts occur because of a decrease in protein, an accumulation of water, and increase in sodium content that disrupts the normal fibers of the lens. The cause of these pathological changes is unknown. The primary symptom of cataracts is a progressive loss of vision. The degree of loss depends on the location and extent of the opacity. Persons with an opacity in the centre portion of the lens can generally see better in dim light when the pupil is dilated. Cortical cataracts involves the anterior, posterior or equatorial cortex of the lens. It progresses at a variable rate and vision is worse in very bright light. [Clinical Manifestation] \- Blurred or distorted vision \- Glare from bright light \- Gradual and aimless loss of vision \- Cloudy white opacity on the pupil. **[Diagnostic Test]** \- There are no particular diagnostic tests for cataract. The diagnosis is made with direct inspection of the lens with an ophthalmoscope after pupil dilation. The progression of cataract is monitored over time. Before surgery the following test may be performed. **A-Scan:** This measures the length of the eye and this is done to estimate the power of the intraocular lens (IOL) that will be needed. \- Keratometry test: This measures the curvature of the cornea and it is also used to determine the power of IOL. \- B -- Scan : is used to evaluate the health of the retina if a dense cataract obscures visualization through an ophthalmoscope. \- Endothelial cell counts: This is done to evaluate the health of the cornea and the ability to withstand surgery. \- Potential Acuity Meter (PAM): This test enables the surgeon to ensure that cataract surgery will be beneficial in increasing the patient's visual acuity. [Management ] Medications do not play a role in the management of cataracts. Anaesthetics, inflammatory agents and antibiotics are all used after surgery to facilitate the healing process and promote patient comfort. Surgery is the treatment of choice for cataract. [Surgical management] -- \- whensurgical removal of the lens is indicated , cataract Surgery is usually done under local anaethesia. Preoperative eye drops produce decreased response to pain and lessened motor activity, oral medication may be given to reduce intraocular pressure. The most popular method of cataract removal is the extraocular cataract extraction (ECCE). The anterior portion of the lens capsule and the capsule contents are removed using techniques such as irrigation and aspiration or pharco-emulsification (ultra-sonic vibration to break up the lens. Cryosurgery technique could also be used for extraction. This is a special technique in which a pencil like instrument with a super cooled (-35^0^ c) is used to touch the exposed lens, freezing it so lens is usually lifted out. Intracapsular extraction involves removal of the entire lens and its surrounding capsule (This method is rarely used anymore). Intraocular lens (IOL) is the preferred method for replacing the focusing power of the lens. The IOL implants are usually implanted at the time of cataract extraction, replacing thick glasses that may provide suboptimal refraction. If IOL is not used, patient will be fitted with appropriate eye glassless or a contact lens to correct refraction after the healing process. [Nursing management] [Preoperative Care] The procedure is usually done in ambulatory surgery centres. Few patients require hospitalization. Explain the procedure to patient. Patient may be asked to perform face scrub before admission, eye lashes may be cut, obtain conjunctival cultures. The pupil of the operative eye is dilated and paralyse before surgery and sedation may be. Assess knowledge level regarding procedure, allay fear and anxiety,administer pre-operative eye drops as prescribed. [Post operative] Most patients are discharged within a few hours. \- Position patient on back or operated site or prevent pressure on operated eye. \- Keep side rails up as necessary for protection. \- Assess pain level: Sudden onset (due to ruptured vessels or suture and may lead to haemorrhage. \- Severe pain accompanied by nausea and vomiting and may be caused by increased intraocular pressure and may require immediate treatment. \- Assess visual acuity in unoperated eye inflammation. Assess for signs of infection like fever,, pain, drainage. \- Assess patient's level of independence. \- Protecting the eye: After any cataract operation, a dressing is applied to the eye and covered with a metal shield to protect the eye from injury. The dressing is usually removed the day or a day after surgery, but a metal eye shield is worn at night for a few weeks until the eye is healed to avoid accidental bumping of the eye during sleep. The patient is cautioned not to sleep on the operative side for 3 to 4 weeks to prevent pressure on the operated eye. Stool softeners is recommended to prevent constipation and straining. \- Patient/family Education: The patient is advised not to allow soap or water to enter the operative eye during face or hair washing. Patient to avoid heavy lifting, active exercise, isometric exercise, straining during defeacation (to prevent abrupt fluctuations in IOP. Give prescribed postoperative medications to relieve inflammation and facilitate heading Anti-inflammatory agents, antibiotics, analgesics are given. Eye drops are commonly prescribed. **Complications:** Infections, bleeding, elevated IOP, Blindness. Strabismus is an ocular misalignment that results from an imbalance in the intraocular muscles. The eyes may be misalignmed in any direction e.gesotropia (turning in) exotropia (turning out), hypertropia (turning up) or hypotropia (turning down). Strabismus is usually associated with childhood, but it can also be a lifelong disorder. Adult strabismus is usually associated with brain tumour, head trauma, stroke and thyroid ophthalmopathy. An estimated 2% to 3% of the general population have some degree of strabismus. **Pathophysiology** The ability to move eyes in all directions and fixate on an object is the function of the six pairs of extraocular muscles. Strabismus interfere with the ability to use binocular vision and focus both eyes on an object, often causing double vision. children with strabismus are frequently able to compensate for the confused image and avoid diplopia. Adults with new onset strabismus are rarely able to compensate. Strabismus is usually caused when the cranial nerves iii (oculomotor) or vi (abducens) have lesion. A strabismus caused by a lesion in either of these nerves results in the lack of innervation of eye muscles and result in a change of eye position. A strabismus may even be a sign of increased intracranial pressure as cranial nerve vi (abducens) is particularly vulnerable to damage from brain swelling as it runs between the cilvus and brain stem. [Management ] Strabismus is diagnosed through a standard visual fields assessment. Glasses with prisms may realign the eyes and restore binocular vision. Encourage eye exercises to strengthen the weak muscles. Surgical correction is the standard treatment. The extraocular muscles are selectively shifted (recession) tightened (reaction) or physically shifted (transposition) to achieve balanced eye movement. Adjustable sutures can be used to achieve an even more accurate alignment. Drug therapy with botulinum neurotoxin A (BOTOX) may eliminate the need per surgery or be used in conjunction with surgery. Patient Education:- Most strabismus surgery is performed on an outpatient basis under local or general anaesthesia. Postoperative care focuses on careful monitoring and preparation of patient for self-care athome. The eye may be patched initially for protection especially if an adjustable suture was used. Patient should avoid strenuous exercise and heavy lifting until approved by surgeon. Patient should be instructed to use cold compress for comfort to combat redness, swelling and irritation. Patient should be instructed to monitor the eye for healing. Conjunctivitis is the inflammation of the conjunctiva. It is a common infection that can occur from a variety of causes. [Types of conjunctivitis ] Conjunctivitis is classified according to its cause. The major causes are microbial infection, allergy and irritating toxic stimuli. Microbial infection may be caused by staphylococci, streptococci, haemophylus influenza, chlamydia, trachomatis and Neisseria gonorrhea. Inflammation is often caused by allergic reactions within the body or by external irritants. Viral agents that can cause conjunctivitis include adenovirus and herpes simplex virus.Acute mucopurulent bacteria conjunctivitis (often called pinkeye) is the most common form of conjunctivitis. It is commonest in school children though it can occur at any age. [Pathophysiology ] The symptoms of conjunctivitis vary in severity. Hyperemia and burning are common initial symptoms that progress rapidly to a mucopurulent exudates, which crusts in the base of the eyelashes and is easily transferred to the un infected eye. Viral infections produce minimal exudate. The conjunctivitis are grossly reddened and inflamed. Invasion of the cornea can result in ulceration and even perforation involvement of the cornea can result in the loss of the eye. The corneal ulcer is usually identified on slit-lamp. Conjunctivitis may be unilateral or bilateral and it usually starts with one eye them spread to the eye. [Clinical manifestations] Foreign body sensation, scratching or burning sensation, itching, photophobia. Purulent discharge [Diagnostic Evaluation] Take comprehensive history from the patient. Evaluate the type of discharge (watery, mucoid, purulent or mucopurulent), type of conjunctivitis reaction (follicular or papillary), presence of pseudo membranes or true membranes, and presence of lymphadenopathy enlargement of lymph nodes where the eye lids drain. Swabbing exudate for culture and sensitivity. [Management] This depends on the type. If involves careful cleansing of the eyelids and the use topical antibiotics. Warm moist compresses may be used to gently remove firm adherent crusts from the eyes, especially in the morning. Warm moist compresses could be applied by \- Use sterile equipment when infection is present, clean technique may be used for allergic reactions. \- Use separate equipment for bilateral eye infections \- wash hands before treating each eye \- Temperature of compress should not exceed 49^o^C (120^o^F) \- Change compresses frequently every 5 minutes as prescribed. Always wash hands first. \- Do not exert pressure on the eyeball \- If sterility is not required, moist heat may be applied by means of a clean face cloth. Dispose the drainage material carefully because it is infections. Common ophthalmic antibiotics include polymyxinB, bacitracin (polysporin), Gentamicin sulfate (Garamycin), chloramphenicol eye drop or ointments. Steroids could also be include, prednisolone acetate, prednisone, methyl/prednisolone (Depo-Medrol), Dexamethasone. The nurse should teach the patient about the disease and its treatment. The infectiousness of the disorder is emphasized, and the patient is encouraged to avoid crowded environments and keep the hands away from the face. Frequent washing of hand is critical especially before and after the use of warm compresses or the installation of the eye medications. Instructs patient to correctly install ophthalmic ointment. The procedure is same to that used for eye drops. The ointment is gently placed directly into the exposed conjunctiva from the inner to the outer canthus, being careful to avoid the eyelash or any part of the eye that would contaminate the tip of the tube. If both drops and ointment are to be used, the ointment is applied lasts is applied last. Millions of persons sustain eye injury each year. Thousands will have permanent blindness as a result. The two major categories of injury are burns and chemical trauma. Chemical burns can occur in the home, school and industrial setting and may, involve either an acid or an alkali substance. Prompt treatment is essential to prevent permanent eye damage. Ultraviolent burns are also a concern and may occur from excess sun exposure. Mechanical trauma can include laceration of the eyelids as well as direct injury to the eye itself. Contusions can cause bleeding into the anterior chamber (hyphema). Corneal injuries present unique problems because they are extremely painful and resistance to infection is low. Scarring of the cornea can impair vision. [Pathophysiology ] The eye is vulnerable to trauma, its natural protective mechanism both prevent and minimize minor eye injury. The heavy orbital bone protects the eye from most blunt mechanical injuries. The eye's natural lubricating system is augmented by tears to help to flush away chemicals and other foreign bodies and the blink reflex protects the eye from most low-impact forces. Acid causes coagulation in the cornea which, although it produces significant local trauma, actually prevents the substance from penetrating and damaging the deeper structures of the eye. Alkaline substances however, penetrate the corneal epithelium and release proteases and collagenases that can cause corneal necrosis and perforation. Penetrating injuries or retained foreign bodies can result in sympathetic ophthalmia, a serious inflammation of the ciliary body, iris and choroid that occursin the injured eye. The cause of the acute inflammation is unknown, but it is believed to be same type of autoimmune response. The inflammation can spread rapidly from uvea to the optic nerve. The uninjured eye becomes inflamed, painful and photophobic with a decline in visual acuity. Prompt aggressive treatment of the eye injuries has decreased the incidence of this rare disorder that can result in the loss of the 'good' eye. [Management] Prompt history of the problem should be taken. First aid measures for eye injury should be done. Burns: ie chemical/flame:- Flush eye immediately for 15minutes with cool water or any available nontoxic liquid. Loose substance on conjunctiva, dirt or insects:- lift upper lid over lower lid to dislodge substance, produce tearing, irrigate eye with water if necessary do not rub eye, then obtain medical attention. Contact injury: contusion, ecchymosis, Laceration: apply cold compresses if no laceration is present; cover eye if laceration is present, then seek medical attention. Penetrating objects: Do not remove objects, place protective shield over the eye, cover uninjured eye to prevent excess movement of injured eye. Chemical burns and immediately treated with copious flushing of the eye with water. A litmus paper may be applied to the conjunctiva to determine the PH if the substance is unknown. Irrigation is continued for 15minutes before patient is transferred for further evaluation and treatment. This simple measure may preserve eye function. Further treatment may include topical antibiotics, steroids and antiglaucoma agents to reduce intraocular pressure. Ultraviolet burns are treated with cool compresses and analgesics. Mechanical trauma also requires prompt care and evaluation. Possible interventions depending on the exact nature of the injury include antibiotics, wound suturing,cycloplegic agent and cold compresses. For penetrating injuries which can result in blindness or loss of the eye ,repair is surgically performed if possible. Contusions are treated with rest and the application of cold compresses to reduce swelling. When penetrating injuries occurs, do not attempt to remove object or to clean the eye. Health educate patient on eye safety and the first aid for eye injuries. Retinal detachment refers to the separation of retinal pigmented epithelium (RPE) from the sensory area of the retina (Rods and cones). A break in the continuity of the retina may first occur from small degenerative holes and tears, which may lead to detachment. [Etiology:] Trauma, inflammation, tumours myopia, loss of lens from a cataract. [Pathophysiology] The retina is a smooth, unbroken, multilayered surface. Degenerative holes or tears in the retina can allow vitreous humour to pass through and initiate a detachment.(rhegamatogenous detachment). The presence of an inflammatory mass, blood clot, tumour can also separate the retina layers (exudative detachment). The vitreous also undergoes some deterioration with ageing and can fall forward exerting a traction pull on the inner lining of the retina causing detachment (traction detachment). Detachment occurs most commonly in patients older than age 40. [Clinical manifestations.] \- Retina detachment may occur slowly or rapidly without pain. \- Patient complains of flushes of light or blurred vision due to stimulation of the retina by vitreous pull \- Patient notes sensation of particles moving in the line of vision. \- A sensation of a veil-like coating coming down, up, sideway in front of the eye if detachment occurs suddenly. [Diagnostic Evaluation ] -Indirect ophthalmoscopy shows gray or opaque retina. The retina is usually transparent. -Slit-lamp examination and three mirror gonioscopy magnify the lesion. -B-Scan ultrasonography may be used to improve the accuracy of the diagnosis. [Management ] [Surgical management] In rhegamatogenous detachment, an attempt is made to reattach the sensory retina to retinal pigmented epithelium (RPE) surgically. The retinal surgeon compresses the sclera to indent the sclera wall from the outside of the eye and bring the two retinal layers in contact with each other. Gas bubbles, silicon oil and liquids may be projected into the vitreous cavity to help push the sensory retinal against the RPE. Argan Laser photocoagulation or cryotherapy is used to 'spot-weld' small holes. Cryosurgery or retinal cryopexy is a commonly used procedure that is combined with a scleral buckling procedure in which the sclera and choroid are buckled toward the break by placing various sizes and shapes of silicone in the region of the break. An encircling band of silicone can also be placed around the eye. The procedure ensures that the choroid remains in contact with the tear during healing and reduce traction pull of any vitreous adhesions. The hole is thereby closed and a water-tight intraretinal space is reestablished. [Nursing Management] [Preoperative care]: Assess for history of trauma or other risk factors. Assess level of anxiety and knowledge regarding procedures. Determine visual limitations and obtain visual description from patient to determine assistance needed. -Instruct patient to remain quiet in prescribed position, patch both eyes. Ensures that patient is oriented to surroundings and can call for assistance. \- Describe preoperative procedures before carrying them out. \- Wash face with antibacterial solution \- Administer preoperative medication as prescribed. Instruct patients not to touch eyes. [Post-operative care] -Assess pain level, visual acuity. Determine patient's ability to ambulate and assume independent activities as tolerated. Caution patient to avoid bumping head. Encourage patient not to cough or sneeze or to perform activities that will increase 1ntra Ocular Pressure. Encourage ambulation and independence.Administer medication for pain, nausea and vomiting as prescribed. [Patient Education and health maintenance ] Encourage self-care at discharge. Instruct patient in the following rapid - eye movement should be avoided for several weeks Driving is restricted, avoid heavier activities, avoid straining, apply a clean, warm, moist wash cloth to eyes and eyelids several times a day. Advise patient to follow-up visit to ophthalmologist within 2weeks. Complications: Glaucoma, infection. This is the inflammation of the uveal tract and affect the iris, the ciliary body and the choroid. It occurs both bilaterally and unilaterally and affects young and middle aged persons. classification \- Uveitis is classified as granulomatous or Nongranulomatous. \- It could also be classified by involved structures. \(1) Anterior Uveitis i.e involving the Iris (Iritis) or Iris andciliary body (Iridocyclitis) \(2) Intermediate Uveitis structure posterior to the lens. \(3) Posterior Uveitis, it affects the choroid (choroiditis), retina. [Non-granulomatousuveitis:] This is the most common type of Uveitis. This occurs principally in the anterior portion of the tract and is thought to be a sensitivity reaction.The onset is acute and it is accompanied by pain, photophobia and blurring of vision. The pupil is constricted, small and irregular. The condition may be unilateral or bilateral. The condition may be recurrent and it can cause anterior synechia (i.e adhesion of peripheral Iris to the cornea and impedes outflow of aqueous humour). Glaucoma and cataractmay result from this. [Granulomatous Uveitis] can involve any portion of the uveal tract most especially the posterior segment. It has a more insidious onset and it tends to be chronic. Symptoms include photophobia, pain which may be minimal. [Management ] Since photophobia is common, patient should be advised to wear dack glasses outdoors. Ciliary spasm and synechia are best avoided through mydriasise.gclycopentolate (cyclogy) and atropine are commonly used. Local corticosteroid drops such as Pred Forte 1% and flarex 0.1% could be instilled 4 to 6 times a day to decrease inflammation. In severe cases, systemic corticosteroid could be administered. Systemic analgesics should be given for pain. This is the removal of the entire eye and part of the optic nerve. Indications:- \(1) Severe injury resulting in prolapsed of Uveal tissue or loss of light projection or perception. \(2) An irritated, blind, painful, deformed or disfigured eye, usually caused by glaucoma, retinal detachment or chronic inflammation. \(3) Intraocular tumours that are untreatable by other means. \(4) An eye without useful information. [Procedure] This involves the separation and cutting of each ocular muscles dissection of the Tenon's Capsule (i.efibrious membrane covering the sclera) the cutting of the optic nerve from the eyeball. The insertion of an orbital implant typically follows, and the conjunctiva is closed. A large pressure dressing is applied over the area. [Evisceration]:- This involves the surgical removal of the intraocular contents through an incision or opening in the cornea or sclera. The optic nerve, sclera, extraocular muscles and sometimes the cornea are left intact. The advantage of this procedure over enucleation is that the final cosmetic result and motility after putting the ocular prosthesis are enhanced while the main disadvantage is the high risk of sympathetic opththalmia. Orbital implants and conformers (i.e ocular prosthesis usually made of silicone rubber) help to maintain the shape of the eye after enucleation or evisceration to prevent a contracted sunken appearance. When orbital implant has been implanted, temporary conformer is placed over the conjunctiva. The placement of the conformer helps to protect the suture line, maintain the fornices, prevent contracture of the socket in preparation for ocular prosthesis and promote the integrity of the eyelids. There are two designs of eye prosthesis: they are anophthalmic ocular prosthesis (which is used when globe is absence) and Sclera spells (which are thinner than anophtalmic prosthesis and are fit over a globe with intact corneal sensation. Eye prosthesis usually last for about six years depending on the quality. Conformers are placed with prosthetic eye when the anophythalmic socket is completely healed. [Management] Removal of an eye has physical, social and psychological effect on any person. In the preparation of the patient, information should be given about the surgical procedure, and placement of orbital implant and conformers and the availability of ocular prosthesis to enhance cosmetic appearance. Patients should also be informed of the large ocular pressure dressing which is usually removed after a week and that ophthalmic ointment is applied in the socket 3times daily. They should be advised to take extra care on ambulation to avoid fall that will resulting injury. Give emotional support and reassurance. Teach patient how to care for the prosthesis. Proper washing of hands before removal prosthesis. **OVERVIEW OF ANATOMY AND PHYSIOLOGY OF THE EAR.** The eras are a part of complex sensory organs located in the middle of both sides of the head at approximately eye level. The position of the ears is importantbecause the use of both ears simultaneously produces binaural hearing, allowing a person to detect direction of sound and aiding in maintaining equilibrium. The ears are housed in the temporal bones of the skull, which are part of both the base and lateral wall of the skull. The temporal bones are the hardest bones in the human body. The ear is divided into three main parts which actually communicate with each other. The three parts include: \- The Outer or External ear \- The Middle ear or Tympanic Cavity \- The Inner ear or Internal ear **[THE EXTERNAL EAR ]** The pinna is primarily composed of cartilage covered by the skin and is attached to the side of the head at approximately a 10^o­­­^ angle. The pinna is the expanded part of the ear that projects out from each lateral aspect of the head. The pinna is made up of yellow elastic cartilage which is covered by skin. Each pinna is grouped and ridged. The outer ridge is called helix. The interior part of the pinna, which is so fit, vascular and consisting of adipose tissue and fabulous tissue covered with skin is called lobule. The external Acoustic meatus (External auditory tube) is an S-Shape tube connecting the pinna to the tympanic membrane (ear drum). The tube is made up of an outer cartilaginous portion covering the first part and an inner bony (or osseous) part covering the rest part of the tube. The cartilaginous part consists of modified sweat glands called ceruminous glands which produce cerumen or ear wax, which functions as a protective mechanism. The sticky consistency of wax, along with fine hairs of the ears help to cleanse the ear canal of foreign matter by trapping dust and filter the air. The funnel shape of the external ear collects sound and channels it toward the ear drum. **[THE MIDDLE EAR (tympanic cavity)]** This is found between the external and internal ear. It is an irregular shaped air-filled cavity within the portion of the temporal bone. The cavity, its contents and the air sacs which open out of it are lined with either simple squamous or cuboidal epithelium. The lateral wall of the middle ear is formed by the tympanic membrane; the roof and floor are formed by the temporal bone; the posterior wall is formed by the temporal bone with openings leading to the mastoid antrum through which air passes to the air cells within the mastoid process; the medial wall is thin layer of temporal bone in which there are two openings which are oval window (it is occluded by part of a small bone called the stapes) and round window (it is occluded by a fine sheet of fibrous tissue. Through the pharyngotympanic (auditory or Eustachian) tube, air reachesthe cavity. This tube extends from the nasopharynx and it is about 4cm long, lined with ciliated columnarepithelium. The presence of air at atmospheric pressure on both sides of the tympanic membrane is maintained by the pharyngotympanic tube and enables the membrane to vibrate when sound waves strikes it. The auditory tube is normally closed but when there is an unequal pressure across the tympanic membrane e.g. at high altitude, it is opened by swallowing or yawning and the ears 'pop' equalizing the pressure again. Auditory ossicles:- These are three very small bones that extend across the middle ear from tympanic membrane to the oval window. They form a series of movable joints with each other and the medial wall of the cavity at the oval window. They are named according to their shapes (outwards inwards); the malleus (hammer) it is a lateral hammer shaped bone. The handle is in contact with the tympanic membrane and the head forms a movable joint with the incus (anvil); The Incus (anvil) is a middle anvil bone. Its body articulates with the malleus the long process with the stapes (stirrup) and its established by the short process, fixed by fibrous tissue to the posterior wall of the tympanic cavity. The stapes (stirrup): Its the medial stirrup shaped bone. Its head articulates with the incus and its footplate fits into the oval window. These three ossicles are held in position by fine ligaments. The Inner Ear The inner ear or labyrinth (meaning maze) contains the organs of hearing and balance. It is described in two parts, the bony labyrinth and the membrane labyrinth. Bony laby\[rinth:- This is a cavity within the temporal bone lined with periosteum. It is larger than and encloses, the membranous labyrinth of the same shape that fits into it, like a tube within a tube. Between the bony and membranous labyrinth there is a layer of watery fluid called perilymph and within the membranous labyrinth there is similarly watery fluid, endolymph. The bony labyrinth consists of the vestibule, cochlea, three semicircular canals. The vestibule is the expanded part very close to the middle ear. It contains the oval and round windows in its lateral wall. The cochlea (this resembles a snails shell. It has a broad base where it continues with the vestibule and a narrow apex, and it spirals round a central bony column. The semicircular canals are three tubes arranged so that one is situated in each of the three planes of space. They are continuous with the vestibule. Membranous labyrinth : This contains endolymph and likes within its bony counterpart it comprises of the vestibule (which contains the utricle and saccule) The cochlea : A cross-section of the cochlea contains three compartments these are the scala vestibuli the sale media or cochlear duct and scala tympani in cross-section the bony cochlea has two compartments containing perilymph: the scale vestibule (which originates at the oval window) and the scala tympani(which ends at the round window) the two compartments continues with each other. The cochlear duct is the part of the membranous labyrinth and is triangular in shape on the basilar membrane or base of the triangle there are supporting cells and specialized cochlear hair cells containing auditory receptors. These cells form the spiral organ (of corti), the sensory organ that responds to vibration by initiating nerve impulses that are then perceived as hearing by the brain the auditory receptors are dendrites of efferent nerves that combine forming the cochlear(auditory) part of the vestibulocochlear nerve 8^th^cranial nerve) which passes through a foramen in the hearing area in the temporal lobe of the cerebrum. **FUNCTIONS OF THE EARS** Hearing :- This is conducted over two pathways: air and bone. Sounds transmitted by air conduction travel over the air-filled external and middle ear through vibration of the tympanic membrane and ossicles Sounds transmitted by bone conduction travel directly through bone to the inner ear by passing the tympanic membrane and ossicles. Normally air conduction is the more efficient pathway. Defect in tympanic membrane or interruption of the ossicular chain disrupt normal air conduction. **SEE THE DIAGRAM OF EAR BELOW** **PHYSIOLOGY OF HEARING** Every sounds produces sound waves or vibration in the air and this travels at about 332 metres (1088feet) per second. The auricle or pinna with its shape helps to collect and concentrate the waves and directs them along the auditory meatus causing the tympanic membrane to vibrate. Vibrations from tympanic membrane are transmitted and amplified through the middle ear by movement of the ossicles (malleus(hammer), Incus (anvil) and stapes (stirrup). At their medial and, the footplate of the stapes rocks to and from in the oval window, setting up fluid waves in the perilymph of the scala vestibuli. Some of the force of these waves is transmitted along the length of the scala vestibule and scala tympanic, but most of the pressure is transmitted into the cochlea duct. This causes a corresponding wave motion in the endolymph, resulting in vibration of the basilar membrane and stimulation of the auditory receptors in the hair cells of the spiral organ (of corti) (which is formed by supporting cells and specialized cochlear hair cells). The nerve impulses generated pass to the brain in the cochlear (auditory) portion of the vestibule cochlear nerve (8^th^ cranial nerve). The fluid wave is finally expended into the middle ear by vibration of the membrane of the round window. The vestibulo cochlear nerve transmits the impulses to the hearing area in the cerebrum where sound is perceived and to various nuclei in the pons and the midbrain. The properties of waves are pitch (which is determined by the frequency of the sound waves and measure in hertz (HZ), volume or intensity (the volume depends on the amplitude of the sound waves and is measured in decibels (db), when there is a very loud noise that is prolong, it can cause damages to the sensitive hair cells of the spiral organ. **[BALANCE AND EQUILIBRIUM]** The semicircular canals have no auditory function although they are closely associated with the cochlea. The semicircular canals and the vestibule (utricle and saccule) are concerned with balance. Any change of position of the head causes motion in the perilymph and endolymph, which bends the hair cells and stimulates the sensory nerve ending in the utricle, saccule and ampullae. The resultant nerve impulses are transmitted by the vestibular nerve which joins the cochlear nerve to form vestibulocochlear nerve. The vestibular branch passes first to the vestibular nucleus, then to the cerebellum. The cerebellum also receiving impulses from the eye and proprioceptors (sensory receptors) in the skeletal muscles and joints. Impulses from these three sources are coordinated and efferent nerve impulses pass to the cerebrum and to skeletal muscles. This result in awareness of body position, maintenance of upright posture and fixing of the eyes on the same point, independently of head movements. [Assessment ] Inspection and palpation are used to examine external ear. The tympanic membrane is inspected with an otoscope and indirect palpation with a pneumatic otoscope The auricle and surrounding tissue should be inspected for deformities, tensions, discharge, size, symmetry and angle of attachment to the head. [OTOSCOPIC EXAMINATION] An otoscope is used to visualize the external auditory canal and eardrum. The canal is straightened prior to insertion of the otoscope speculum to afford better visualization. This is accomplished by gently pulling in children the auricle is pulled slightly down and back. [EVALUATION OF GROSS AUDITORY ACUITY:-] A general estimation of hearing can be made by assessing the patient's ability to hear a whispered phase or a ticking watch, testing one ear at a time.Whisper test, weber test, Rinne test. [Whisper test:-] stand about 1 to 2 feet away from then patient tell him /her to use palm to occlude the untested ear out of the sight of the patient, whisper some words. Patient with normal acuity can repeat whisper words correctly. [Rinne test for air and bone conduction:-]tunning fork is stroke and place about 2 inches from the opening of the ear canal (for air conduction) and against the mastoid bone (for bone conduction). Normal sound heard by air conduction is audible longer than sound heard by bone conduction. This test (Rinne) is used to distinguish between conductive and sensorineural hearing losses. In conductive hearing loss, bone-conducted sound is heard as long as or longer than air-conducted sound. While in sensorineural hearing loss, air-conducted sound is audible longer them bone conducted sound. Weber test (bone conduction testy). The tuning fork is tapped and placed in the patient's head or fore head. The sound is heard better in the affected ear. Diagnostic Evaluation. \- audiometry:- this is used to detect hearing loss. It is one of the most important diagnostic instrument.The audiometric testing is of two kinds which are pure or musical tone (the louder the tone before the patient perceives if the greater the hearing loss) and speech and audiometry, in which the spoken word is used to determine the ability to hear and disseminate sounds and words. Three characteristics are important when evaluating hearing loss viz frequency pitch and intensity The stimulus may be applied directly over the ear canal to determine our conduction (conductive hearing loss) or over the mastoid to determine air conduction (sensorineural hearing loss). Results are plotted on a graph known as audiogram. The patient wears ear phones and signal upon hearing a tone Electronystagmography (ENG) This is the measurement of changes in electrical potentials created by eye movement during spontaneous, positional calorically evoked nystagmus it is used to evaluate the oculomotor and vestibular system to differentiate the cause of vertigo tinnitus and hearing loss of unknown origin. It is also used in diagnosing Meniere's diseases. The test is done in a darkened room and it last for about an hour. Electrodes are taped to the patient is face and patient is asked to look in different directions and change positions. Air is gently blown into the external ear canal. Patient should avoid heavy in meal before the procedures. Caffeine, alcohol, sedatives, should be held for about five days before procedure. There are multiple causes of hearing loss and range of hearing loss vanes from mild high frequency loss to severe loss with complete inability to understand the spoken word. Two major types are conductive and sensorineural. There are about 20 million Americans with hearing loss. [Classification /Types of hearing loss:-] 1\. Conductive hearing loss:-hearing loss due to an impairment of the external or middle ear or both. If causative problem cannot be corrected a hearing aid may help 2\. Sensorineural (perceptive) loss:-hearing loss due to disease of the inner ear or nerve pathways, sensitivity to and dissemination of sounds are impaired.Hearing aids usually are helpful 3\. Central hearing loss: -- Damage to the brain's auditory pathways or auditory centre 4\. Psychogenic hearing loss :- hearing loss without physical problem. 5\. Functional hearing loss:- no organic lesion can be found. 6\. -Neural Hearing loss: This is sensorineural hearing loss originating in the nerve or brainstem 7.Fluctuating Hearing loss: A sensorineural hearing loss that varies with time 8\. Sensory Hearing loss: A sensorineural hearing loss originating in the cochlea and involving the hair cells and nerve endings. 9\. Sudden Hearing loss: A sensorineural hearing loss with a sudden onset 10\. - Mixed Hearing loss: Elements of both conduction and sensorineural hearing loss. [Clinical manifestations] Tinnitus, increasing in ability to hear in groups, change in attitude Symptoms include :- speech deterioration, fatigue, indifference, insecurity, suspiciousness, false pride, loneliness and unhappiness, tendency to dominate conversation. [Risk factors for hearing loss] -family history sensorineural impairment -congenital malformation of the cranial structure ear -low birth weight (\