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Questions and Answers
What is the function of the refracting tissues in the eye?
What is the function of the refracting tissues in the eye?
Focus light onto light-sensitive tissues to give a clear, sharp image.
Which tissues make up the refracting tissues in the eye?
Which tissues make up the refracting tissues in the eye?
Diseases affecting the function of light-sensitive tissues directly affect visual acuity. (True/False)
Diseases affecting the function of light-sensitive tissues directly affect visual acuity. (True/False)
True
___ is defined as the smallest object resolvable by the eye at a given distance.
___ is defined as the smallest object resolvable by the eye at a given distance.
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The technique for measuring vision with corrective prescription lenses is known as ____.
The technique for measuring vision with corrective prescription lenses is known as ____.
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Match the following eye components with their functions:
Match the following eye components with their functions:
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Which of the following is a cause of proptosis?
Which of the following is a cause of proptosis?
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Orbital cellulitis is a localized inflammation affecting the orbital soft tissue.
Orbital cellulitis is a localized inflammation affecting the orbital soft tissue.
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What is the main cause of unilateral proptosis in children?
What is the main cause of unilateral proptosis in children?
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What is the primary sign of squamous blepharitis, as described in the text?
What is the primary sign of squamous blepharitis, as described in the text?
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What is a common complication of squamous blepharitis?
What is a common complication of squamous blepharitis?
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Angular blepharitis is associated with infestation of lashes by ________.
Angular blepharitis is associated with infestation of lashes by ________.
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Zinc sulfate eye drops are used to neutralize the action of proteolytic enzymes in parasitic blepharitis.
Zinc sulfate eye drops are used to neutralize the action of proteolytic enzymes in parasitic blepharitis.
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Match the abnormality of eyelashes with their descriptions:
Match the abnormality of eyelashes with their descriptions:
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What is the definition of Meibomian gland dysfunction?
What is the definition of Meibomian gland dysfunction?
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What are the initial symptoms of sinus-involving mucormycosis?
What are the initial symptoms of sinus-involving mucormycosis?
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Rhino-orbital mucormycosis is commonly seen in patients with a history of diabetes, chronic steroid use, and immunosuppression.
Rhino-orbital mucormycosis is commonly seen in patients with a history of diabetes, chronic steroid use, and immunosuppression.
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What is the main function of the eyelids? Maintenance of ocular surface integrity & protecting the eyes from injury and excessive light. 2.________ barrier to a variety of insults.
What is the main function of the eyelids? Maintenance of ocular surface integrity & protecting the eyes from injury and excessive light. 2.________ barrier to a variety of insults.
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What is the mainstay of medical treatment for mucormycosis?
What is the mainstay of medical treatment for mucormycosis?
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What is the most common type of acquired ptosis?
What is the most common type of acquired ptosis?
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What is the most common type of congenital ptosis?
What is the most common type of congenital ptosis?
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Which condition is associated with Marcus-Gunn jaw winking?
Which condition is associated with Marcus-Gunn jaw winking?
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Match the eyelid gland with its description:
Match the eyelid gland with its description:
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Amblyopia can occur in cases of long-standing congenital ptosis.
Amblyopia can occur in cases of long-standing congenital ptosis.
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_______ causes incomplete closure of the eyelids.
_______ causes incomplete closure of the eyelids.
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What can cause the formation of a grayish membrane on the conjunctival surface?
What can cause the formation of a grayish membrane on the conjunctival surface?
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Which of the following may lead to Symblepharon?
Which of the following may lead to Symblepharon?
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Subconjunctival hemorrhage can be commonly seen in entero or coxsackieviruses.
Subconjunctival hemorrhage can be commonly seen in entero or coxsackieviruses.
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The causative agent for Acute infective conjunctivitis can include _________
The causative agent for Acute infective conjunctivitis can include _________
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Where are the puncti located in the lacrimal drainage system?
Where are the puncti located in the lacrimal drainage system?
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What are the parts of the lacrimal sac?
What are the parts of the lacrimal sac?
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What is the definition of chronic dacryocystitis?
What is the definition of chronic dacryocystitis?
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Which valve guards the opening of the nasolacrimal duct in the inferior meatus of the nose? Hasner's _____
Which valve guards the opening of the nasolacrimal duct in the inferior meatus of the nose? Hasner's _____
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What is the physiology behind tear drainage for the lacrimal sac to the nasolacrimal duct influenced by?
What is the physiology behind tear drainage for the lacrimal sac to the nasolacrimal duct influenced by?
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Tears pass through the nasolacrimal drainage system to the ears. (True/False)
Tears pass through the nasolacrimal drainage system to the ears. (True/False)
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What are the predisposing and precipitating factors for chronic dacryocystitis?
What are the predisposing and precipitating factors for chronic dacryocystitis?
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Match the following conjunctival disorders with their descriptions:
Match the following conjunctival disorders with their descriptions:
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The ________ serves as a tear drainage surgical procedure to bypass an NLD obstruction.
The ________ serves as a tear drainage surgical procedure to bypass an NLD obstruction.
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Chronic conjunctivitis is a potential complication of chronic dacryocystitis.
Chronic conjunctivitis is a potential complication of chronic dacryocystitis.
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Study Notes
Eye Structure and Function
- The eye is like a ball with most of it sitting in the orbit.
- The eye is cushioned by orbital fats and fibrous tissues, and moved by extraocular muscles.
- The eye has a multi-layered wall, and the space inside contains the lens and fluids (vitreous and aqueous humor).
- The eye detects light and converts it into electro-chemical impulses transmitted to the brain via the optic nerve and visual pathway to the visual cortex.
Structure of the Eye
- The wall of the eye has three layers: outer (cornea and sclera), middle (iris, ciliary body, and choroid), and inner (retina).
- The eye has three types of tissue: refracting (focus light), light-sensitive (detect light), and support (structural).
Clinical Examination of the Eye
- Visual acuity (VA) testing measures the smallest object resolvable by the eye at a given distance.
- VA is expressed as a fraction (e.g., 6/6, 6/18).
- Low-vision testing involves measuring the distance at which a patient can see the largest optotype.
External Head and Face Examination
- Inspect the patient for disturbances in head and face bony structures, skin, lymph nodes, mouth, eyelids, lacrimal system, and globe position.
Pupil Examination
- Examine the pupil's size, shape, and reaction to light.
- A normal response is constricted pupils in response to light.
Anterior Segment Examination (Slitlamp)
- Use a slitlamp to visualize the anterior segment of the eye, including the cornea, conjunctiva, sclera, anterior chamber, iris, lens, and vitreous.
Posterior Segment Examination (Fundoscopy)
- Examine the posterior segment of the eye, including the retina, optic nerve, and retinal blood vessels.
Intraocular Pressure (IOP) Measurement
- Measure IOP using applanation tonometry or indentation tonometry.
- IOP varies in the population, with a mean of 16 mmHg and a standard deviation of 3 mmHg.
Ocular Motility Testing
- Examine ocular motility by asking the patient to follow a target with their eyes.
Refraction and Best-Corrected Visual Acuity (BCVA)
- Measure refraction using automated or manual methods.
- BCVA is the best possible visual acuity with corrective lenses.
Diseases of the Ocular Adnexa
- The ocular adnexa include the eyelids, lacrimal gland, and orbit.
- Diseases of the ocular adnexa can affect the eye's protective structure and function.
Orbital Diseases
- Orbital diseases can cause proptosis, which is an abnormal protrusion of the globe due to increased intraorbital pressure.
- Causes of proptosis include congenital, acquired, endocrine, traumatic, inflammatory, neoplastic, and vascular disorders.
Workup of a Case of Proptosis
- Take a thorough history and examination, including measuring the degree and direction of proptosis.
- Investigations may include lab tests, imaging (CT or MRI), and biopsy.Here are the study notes for the given text:
- Diseases of the Ocular Adnexa*
Thyroid Eye Disease (TED)
- Age/sex: Middle-aged females
- Risk factors: Smoking, history of radioactive iodine treatment for thyroid dysfunction
- Pathogenesis: Autoimmune disease with infiltration of the orbit by plasma cells and lymphocytes, leading to extraocular muscle enlargement and fibrosis
- Manifestations:
- General: Symptoms and signs of hypo/hyperthyroidism
- Ocular:
- Hyperemia along the recti muscles insertions
- Lid signs: lid retraction (Dalrymple sign), lid lag on downgaze (Von Graefe's sign), infrequent blinking (Stellwag sign)
- Restrictive stage: Proptosis and limited motility (diplopia)
- Complications:
- Exposure keratitis
- Compressive optic neuropathy
- 2ry glaucoma
- Investigation:
- Thyroid function test (T3, T4, TSH)
- CT, MRI: EOM enlargement
- Treatment:
- Treatment and prophylaxis of exposure keratitis
- TTT of thyrotoxicosis (may not improve)
- Infiltrative stage: systemic steroids, immunosuppressive therapy, and radiotherapy
- Surgical: orbital decompression if severe exposure or compressive optic neuropathy
- EOM recession if diplopia in primary or reading position (+/- relieving prisms)
Orbital Cellulitis
- Incidence: Main cause of unilateral proptosis in children
- Source of infection:
- Sinusitis (especially ethmoidal)
- Trauma: surgical, penetrating trauma
- Symptoms:
- General: Fever, headache, anorexia, malaise
- Ocular: Severe pain, hot and tender skin
- Signs: Signs of orbital disease
- D.D: Preseptal cellulitis: no ophthalmoplegia, no proptosis
- Complications:
- Spread: eye (panophthalmitis), brain (cavernous sinus thrombosis, meningitis, brain abscess)
- Optic neuritis and CRVO
- Exposure keratitis
- Localization: orbital abscess and fistula
- Healing by fibrosis: Enophthalmos with restricted motility (frozen orbit)
- Investigation:
- CBC: leukocytosis
- CT scan: detect sinusitis and abscess localization
- Treatment:
- Treatment and prophylaxis of exposure keratitis
- Hospitalization
- Antibiotics (IV or IM broad-spectrum G+/G- and anaerobes)
- Hot fomentations and analgesia
- Surgical: if abscess—drain
Cavernous Sinus Thrombosis (CST)
- Etiology:
- Infection in the dangerous area of the face (angular vein connected to ophthalmic vein)
- Lid: stye
- Orbit: cellulitis
- Acute dacryocystitis
- Globe: panophthalmitis
- Infection in the dangerous area of the face (angular vein connected to ophthalmic vein)
- CST appears as orbital cellulitis or complicates orbital cellulitis, but differs in:
- Associated with more general symptoms and drowsiness
- Severe congestive signs
- Other eye affection (starting by 6th nerve palsy—diplopia and esotropia)
- Mastoid edema due to emissary vein affection
- 25% mortality rate (brain abscess, septicemia, and meningitis)
Mucormycosis
- Epidemiology:
- Associated with diabetes mellitus (especially with diabetic ketoacidosis)
- Other associated conditions: neutropenia, hematologic malignancy, chronic steroid or immunosuppressive drug use, history of transplant, and history of multiple blood transfusions
- Diagnosis:
- Signs and Symptoms:
- Initial symptoms of sinus-involving mucormycosis are consistent with acute or chronic sinusitis
- Involvement of the orbit is heralded by findings of chemosis, proptosis, extra-ocular motility deficits, and multiple cranial neuropathies, and loss of vision
- Direct visualization of the nasal mucosa and para-nasal sinuses reveals dark, necrotic tissue and a characteristic black eschar
- Investigation:
- CT of the orbits and/or para-nasal sinuses can show contrast-enhancing hypodense soft-tissue thickening of the involved sinuses
- Definitive diagnosis of mucormycosis can be made via histopathologic evaluation of tissue via biopsy or scraping
- Signs and Symptoms:
- Management:
- General treatment:
- Early recognition and initiation of appropriate treatment is very important
- Urgent correction of underlying metabolic derangements such as hyperglycemia and metabolic ketoacidosis, and tapering of corticosteroids or immunosuppressive medications
- The mainstay of medical treatment remains intravenous anti-fungals
- General treatment:
Anatomy and Physiology of the Eyelids
- Functions of the eyelids:
- Maintenance of ocular surface integrity and protection of the eyes from injury and excessive light
- Mechanical barrier to a variety of insults
- Sweeping mechanism to remove debris from the cornea (blink reflex) and spread tears over the surface of the eyes
- Contribution to the production (Meibomian gland function) and drainage (lacrimal pump and capillarity of the lid margin) of the tear film
- Gross anatomy:
- Position: In the primary position, the upper lid covers the upper 1/6 of the cornea, and the lower lid is at the level of the lower limbus
- Palpebral fissure: Opening of the two lids being separate apart
- Canthi: Angles of the palpebral fissure
- Upper lid crease: Develops as the upper lids rise due to the attachment of the levator muscle
- Minute anatomy:
- Skin
- Subcutaneous areolar tissue
- Striated muscle layer
- Sub-muscular space
- Septo-tarsal layer
- Palpebral conjunctiva
- Blood supply:
- Arteries: Medial and lateral palpebral arteries from the ophthalmic and lacrimal arteries
- Lymphatic drainage:
- Lateral: pre-auricular LN
- Medial: submaxillary LN
- Then both in deep cervical LN
- Nerve supply:
- Motor: orbicularis oculi (VII cranial nerve), levator palpebrae superioris (III cranial nerve), Muller's muscle (sympathetic fibers)
- Sensory: branches of the trigeminal nerve (V)### Lid Hygiene and Treatment
- Apply warm compresses for 30 minutes, twice daily
- Topical treatments: antibiotics, lubrication, and tear substitutes; corticosteroids for severe inflammation
- Oral tetracyclines: doxycycline 100 mg once daily
- Dietary recommendations: high omega-3 fats for ocular surface health
Abnormalities of Eyelashes
- Trichiasis: abnormal direction of lashes, normal position
- Distichiasis: extra row of lashes behind the grey line, arising from Meibomian gland orifices
- Metaplastic lashes: abnormal position of lashes
Acquired Trichiasis
- Types:
- Rubbing lashes (4 lashes or less)
- Trichiasis (more than 4 lashes rubbing against the cornea and conjunctiva)
- Etiology:
- Trachoma
- Lid margin inflammation
- Clinical picture:
- Corneal symptoms: foreign body sensation, lacrimation, photophobia, and blepharospasm
- Redness of the eye: conjunctival hyperemia
- Signs: misdirected lashes, conjunctival hyperemia, trichiasis-entropion
Complications
- Chronic conjunctivitis
- Corneal ulceration, opacification, vascularization, keratinization, and epithelial plaque formation
Treatment
- Rubbing lashes (Less than 4 lashes):
- Epilation (temporary)
- Destruction of the hair follicle by laser photocoagulation, cryotherapy, thermal coagulation, or electrolysis
- Trichiasis (more than 4 lashes):
- Trichiasis alone:
- Upper lid: Van-Millengen's operation (displace rubbing lashes away from the eyeball)
- Lower lid: Webster's operation (putting a mucous membrane graft in the sulcus subtarsalis)
- Trichiasis with entropion:
- Upper lid: Snellen's operation
- Lower lid: Webster's operation
- Trans-positioning of the lid skin by Z-plasty
- Trichiasis alone:
Lid Position Abnormalities
- Ectropion:
- Definition: Rolling outward of the lid margin
- Types:
- In the upper lid:
- Cicatricial (scarring of the anterior lamella)
- In the lower lid:
- Cicatricial (scarring of the anterior lamella)
- Senile (involutional)
- Paralytic
- Congenital
- In the upper lid:
- Clinical picture:
- Symptoms: watering of the eye, bad cosmetic appearance
- Signs: exposure of the punctum, palpebral conjunctiva, bulbar and forniceal conjunctiva
- Complications:
- Epiphora
- Eczema
- Exposure keratitis
Entropion
- Definition: Rolling inward of the lid margin
- Types:
- In the upper lid:
- Cicatricial (scarring of the posterior lamella)
- In the lower lid:
- Cicatricial (scarring of the posterior lamella)
- Senile (involutional)
- Spastic
- Congenital
- In the upper lid:
- Clinical picture:
- Symptoms: as for trichiasis
- Signs: rolling inward of the lid margin, signs of the cause of trichiasis
- Complications: as for trichiasis
Blepharoptosis
- Definition: Drooping of the upper lid more than 2 mm
- Etiology and classification:
- According to the site of primary pathology along the pathway from the nerve supply of the levator muscle to its insertion at the lid
- Dysgenetic, aponeurotic, neurogenic, myogenic, and mechanical
- Clinical assessment:
- History: duration, variability, and impact on vision
- Examination:
- Facial appearance
- Degree of ptosis
- Levator function
- Upper lid crease height
- Extraocular movements
- Pupil
- Visual acuity
- Protective mechanisms: Bell's phenomenon, corneal sensation, lid closure for lagophthalmos
Management of Ptosis
- Treatment of acquired ptosis:
- Traumatic ptosis: wait 6 months for regeneration of 3rd nerve fibers or recovery of lacerated levator muscle and absorption of edema
- Mechanical ptosis: removal of the cause
- Paralytic ptosis: control the underlying etiology and squint surgery
- Involutional aponeurotic ptosis: aponeurotic surgery
- Myogenic ptosis: medication control (prostigmine)
- Treatment of congenital ptosis:
- Timing: early (severe ptosis with fear of amblyopia) or late (less severe ptosis)
- Type of surgical intervention: according to the levator function, either levator resection or frontalis sling
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Description
Learn about the anatomy and functions of the human eye, including its position in the orbit, protective structures, and surrounding tissues.
