أسئلة المحاضرة السادسة رمد (قبل التعديل)

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Questions and Answers

What is the primary function of the cornea regarding light?

Regenerate rapidly after damage

Protect against infection

Store nutrients for the eye

Act as a primary refractive medium (correct)

Which layer of the cornea does not regenerate after damage?

Stroma

Epithelium

Bowman's membrane (correct)

Endothelium (correct)

What is the normal endothelial cell count at birth?

Around 4000 cells/mm2

Less than 2000 cells/mm2

About 2500 cells/mm2

Greater than 3000 cells/mm2 (correct)

How does corneal thickness vary from the center to the periphery?

Thinner at the center than the periphery Signup and view all the answers

What device is used to measure the corneal power?

Keratometer Signup and view all the answers

What is the typical power of the cornea, measured in diopters?

42 D Signup and view all the answers

What happens to endothelial cell density with age?

Decreases by 0.6% per year Signup and view all the answers

At which anatomical structure does Descemet’s membrane end?

Schwalb’s line Signup and view all the answers

Which of the following maps can corneal tomography determine?

Corneal power map Signup and view all the answers

What supplies oxygen to the cornea?

Tear film Signup and view all the answers

Which of the following is NOT a cause of corneal opacity?

Corneal perforation Signup and view all the answers

Which nerves are involved in the corneal sensitivity reflex?

Trigeminal nerve and facial nerve Signup and view all the answers

What structure primarily provides glucose and other nutrients to the cornea?

Aqueous humor Signup and view all the answers

Which condition can cause decreased or lost corneal sensations?

Corneal infection Signup and view all the answers

What is the primary factor that maintains corneal transparency?

Uniformity of collagen bundles Signup and view all the answers

Which term describes a faint opacity from which the iris structure can still be seen?

Nebula Signup and view all the answers

What characterizes leucoma?

A dense opacity preventing visibility of the iris Signup and view all the answers

Which surgical procedure is associated with central corneal opacity?

Deep anterior lamellar keratoplasty (DALK) Signup and view all the answers

What is the main predisposing factor for typical corneal ulcers?

Chronic dacryocystitis Signup and view all the answers

Which organism is most commonly associated with the use of contact lenses?

Pseudomonas Signup and view all the answers

What best describes keratectasia?

Loss of stroma leading to corneal thinning Signup and view all the answers

Which of the following is a type of bacterial corneal ulcer?

Marginal catarrhal ulcer Signup and view all the answers

What distinguishes typical from atypical corneal ulcers?

Type of bacterial infection causing them Signup and view all the answers

Which condition is NOT a risk factor for corneal ulcers?

Frequent blinking Signup and view all the answers

Which organism is most likely responsible for filamentous keratitis associated with trauma from a vegetable or contact lens?

Aspergillus Signup and view all the answers

What is a common symptom of keratitis caused by yeast in immunocompromised patients?

Lacrimation Signup and view all the answers

Which of the following is a suggested management approach for stromal keratitis?

Systemic antifungal medications Signup and view all the answers

In the treatment of epithelial keratitis, which topical medication is commonly used?

Ganciclovir Signup and view all the answers

What is a typical sign of keratitis as seen under examination?

Feathery borders Signup and view all the answers

Which symptom is associated with spasm of the constrictor pupillae muscle?

Photophobia Signup and view all the answers

What complication occurs after corneal perforation that is larger in size than before?

Peripheral large Signup and view all the answers

Which treatment is NOT recommended for immediate management of corneal issues?

Corticosteroids Signup and view all the answers

What symptom indicates the presence of nerve endings exposure?

Pain due to nerve endings exposure Signup and view all the answers

Which of the following is a sign of corneal perforation?

Hypotony and collapse of AC Signup and view all the answers

What must be observed in the eyes immediately after treating for infection?

Eye protection measures Signup and view all the answers

What type of corneal opacity occurs before perforation?

Central small opacity Signup and view all the answers

Which sign is used to measure the degree of anterior chamber inflammation?

Cells and flare Signup and view all the answers

What is the primary source of oxygen for the cornea?

Tear film Signup and view all the answers

Which of the following does NOT contribute to corneal transparency?

Presence of blood vessels Signup and view all the answers

What is the effect of extended use of contact lenses on the cornea?

Induces corneal infection Signup and view all the answers

Which condition is least likely to cause corneal opacity?

Normal aging process Signup and view all the answers

Which of the following factors most directly influences corneal sensitivity?

Afferent nerve pathways Signup and view all the answers

Which of the following statements regarding corneal healing is true?

Corneal epithelium heals faster than other layers. Signup and view all the answers

Which of the following is a common symptom of filamentous keratitis?

Lacrimation Signup and view all the answers

Corneal sensitivity testing may demonstrate decreased sensitivity due to which of the following factors?

Compression by tumors Signup and view all the answers

What is the management approach for stromal keratitis?

Topical steroids and antiherpetic medications Signup and view all the answers

What type of corneal opacity is characterized by faint opacity from which the iris structure can still be seen?

Nebula Signup and view all the answers

Which staining technique is used to observe the features of epithelial keratitis?

Fluorescein and rose Bengal staining Signup and view all the answers

What is a distinctive sign of yeast-related keratitis in an immunocompromised individual?

Satellite lesions Signup and view all the answers

What is the typical duration for topical antifungal treatment in cases of keratitis?

6-8 weeks Signup and view all the answers

What distinguishes infective corneal ulcers from non-infective ones?

Pus with living inflammatory cells Signup and view all the answers

Which procedure is least likely to be performed for central corneal opacity?

Colored contact lens application Signup and view all the answers

What is the most common organism responsible for typical corneal ulcers?

Pneumococci Signup and view all the answers

Which risk factor is NOT associated with the development of corneal ulcers?

Pneumococcal infection history Signup and view all the answers

In which type of corneal opacity can the iris structure still be seen?

Leucoma Signup and view all the answers

Which organism is most likely to invade intact corneal epithelium among the listed pathogens?

Hemophilus Signup and view all the answers

What treatment is typically NOT used for corneal ulcers with pus?

Surgical drainage Signup and view all the answers

Which of the following conditions is classified as a non-infective corneal ulcer?

Exposure keratitis Signup and view all the answers

What characteristic distinguishes Bowman's membrane from the other layers of the cornea?

It is a condensed layer that does not regenerate. Signup and view all the answers

Which measurement indicates the health of the corneal endothelial cells?

Density of endothelial cells. Signup and view all the answers

What role does the cornea play in the overall refractive power of the eye?

It provides the majority of the eye's refractive power. Signup and view all the answers

Which factor is primarily responsible for the variation in corneal thickness between the center and periphery?

Geometric curvature of the cornea. Signup and view all the answers

What is the significance of the corneal power measurement?

It represents how efficiently light is refracted by the cornea. Signup and view all the answers

What changes occur at the limbus in relation to the corneal structure?

The epithelium merges with conjunctival epithelium. Signup and view all the answers

How does endothelial cell density change with aging, and what is its impact?

It decreases, which may precipitate corneal edema. Signup and view all the answers

What is the primary composition of the stroma in the cornea?

Composed of densely packed collagen fibers. Signup and view all the answers

Which of the following symptoms is primarily caused by spasm of the orbicularis oculi muscle?

Blepharospasm Signup and view all the answers

What complication is characterized by a total iris prolapse as a result of a corneal perforation?

Central Large Signup and view all the answers

Which sign indicates a positive result on fluorescein staining related to corneal integrity?

Corneal ulceration Signup and view all the answers

Which of the following is an expected sign immediately after corneal perforation?

Hypotony and collapse of the anterior chamber Signup and view all the answers

What treatment is specifically indicated to prevent synechia after ocular trauma?

Mydriatics Signup and view all the answers

Which complication is associated with the development of peripheral synechia in response to anterior inflammation?

Leucoma adherent Signup and view all the answers

What immediate action is NOT recommended after a corneal perforation has occurred?

Apply steroids Signup and view all the answers

Which of the following represents a typical sign of corneal opacity observed before perforation occurs?

Corneal vascularization Signup and view all the answers

What are the distinguishing symptoms associated with filamentous keratitis?

Symptoms include lacrimation, photophobia, haloes, blurring of vision, and little pain. Signup and view all the answers

In the management of yeast keratitis in immunocompromised patients, what treatment is typically recommended?

Topical antifungal treatments such as Natamycin or Voriconazole are recommended for 6-8 weeks. Signup and view all the answers

Which staining techniques are utilized to observe epithelial keratitis, and what do they reveal?

Rose Bengal staining is used for the edges, and fluorescein staining for the floor, indicating different features of the keratitis. Signup and view all the answers

What is a common sign indicative of fungal keratitis as observed during examination?

A common sign includes feathery borders along with satellite lesions. Signup and view all the answers

What are the primary differences between epithelial keratitis and stromal keratitis in terms of treatment?

Epithelial keratitis is treated with topical antiherpetic medication, while stromal keratitis requires systemic treatment along with topical steroids. Signup and view all the answers

What nutrients are supplied to the cornea by the aqueous humor?

Glucose and other nutrients. Signup and view all the answers

Which nerve is responsible for the afferent pathway in the corneal sensitivity reflex?

Nasociliary nerve. Signup and view all the answers

Name a cause of decreased corneal sensations related to trauma.

Trauma. Signup and view all the answers

Identify a non-infectious cause of corneal opacity.

Corneal degeneration. Signup and view all the answers

What is the response of the cornea's sensitivity reflex when stimulated?

Blinking. Signup and view all the answers

What condition can result from extended use of contact lenses?

Corneal pannus. Signup and view all the answers

Describe a factor that contributes to corneal transparency.

Avascular nature of the cornea. Signup and view all the answers

What term describes a more severe opacity from which iris details are not visible?

Macula. Signup and view all the answers

What is the main cause of pus in the hypopion corneal ulcer?

Bacterial infection is the primary cause of pus in hypopion corneal ulcers. Signup and view all the answers

What type of corneal opacity cannot reveal the iris structure?

Leucoma is the type of corneal opacity from which the iris structure cannot be seen. Signup and view all the answers

What surgical procedure is typically associated with superficial corneal opacity?

Phototherapeutic keratectomy (PTK) is associated with superficial corneal opacity. Signup and view all the answers

Which organism is most notably linked to contact lens-related corneal complications?

Pseudomonas is the most common organism associated with contact lens-related infections. Signup and view all the answers

What condition is characterized by corneal thinning and dense scarring?

Keratectasia is characterized by loss of corneal stroma, leading to thinning and scarring. Signup and view all the answers

What type of corneal ulcer is primarily caused by pneumococci?

Typical corneal ulcers are primarily caused by pneumococci in 70-80% of cases. Signup and view all the answers

What is the most significant risk factor contributing to corneal ulcers?

Chronic dacryocystitis is the main predisposing factor for corneal ulcers. Signup and view all the answers

Name a condition that can lead to exposure keratitis.

Lagophthalmos can lead to exposure keratitis due to inadequate eyelid closure. Signup and view all the answers

What are the main components of the stroma layer of the cornea?

The stroma contains uniformly spaced collagen fibers and makes up 90% of corneal thickness. Signup and view all the answers

Explain the function of Descemet's membrane in the cornea.

Descemet's membrane serves as the basement membrane for the endothelium, providing structural support. Signup and view all the answers

How does the cornea's refractive power depend on its curvature?

The anesthetics shape of the cornea, with an anterior curvature of 7.8 mm and posterior of 6.5 mm, influences its refractive power. Signup and view all the answers

What role does Bowman's membrane play in the cornea's structure?

Bowman's membrane is a condensed superficial layer of stroma that does not regenerate after injury. Signup and view all the answers

What is the typical corneal endothelial cell density at birth, and how does it change with age?

The typical density is greater than 3000 cells/mm2 at birth, decreasing by 0.6% per year as a person ages. Signup and view all the answers

Describe the transition of the corneal layers at the limbus.

At the limbus, the corneal epithelium continues with the conjunctival epithelium, while Bowman's membrane transitions to conjunctival stroma. Signup and view all the answers

What are the implications of a decrease in endothelial cell density below 500 cells/cm2?

A decrease below this threshold may lead to corneal edema and compromised optical function. Signup and view all the answers

How is corneal thickness measured and how does it vary from the center to the periphery?

Corneal thickness is measured using ultrasound pachymetry, varying from 500-550 microns at the center to 500-900 microns at the periphery. Signup and view all the answers

What are the symptoms that indicate nerve endings exposure in the eye?

Pain due to exposure of nerve endings and ciliary muscle spasm, along with photophobia and lacrimation. Signup and view all the answers

Which sign indicates a significant decrease in intraocular pressure (IOP) after corneal perforation?

Sudden decrease in IOP. Signup and view all the answers

Identify at least two complications that may arise from a central large corneal perforation.

Total iris prolapse and lens dislocation/expulsion. Signup and view all the answers

What is the condition characterized by the formation of peripheral anterior synechia in peripheral small corneal perforations?

Anterior synechia. Signup and view all the answers

What immediate management steps should be taken to prevent complications after corneal scrap culture?

Start broad-spectrum antibiotics and administer mydriatics to prevent synechia. Signup and view all the answers

Explain the significance of fluorescein staining in the context of corneal ulcers.

Positive fluorescein staining indicates corneal damage and facilitates the diagnosis of ulcers. Signup and view all the answers

What role do vitamins A and C play in managing corneal issues?

Vitamins A and C are used for promoting healing and improving eye health. Signup and view all the answers

Describe the effect of contact lens use on corneal sensitivity.

The use of contact lenses can lead to decreased corneal sensitivity. Signup and view all the answers

What are two common symptoms associated with epithelial keratitis?

Lacrimation and photophobia. Signup and view all the answers

Describe the typical management approach for filamentous keratitis caused by Aspergillus or Fusarium.

Topical antifungals like Natamycin or Voriconazole for 6-8 weeks, along with topical antibiotics and lubricants. Signup and view all the answers

What is the importance of double staining with rose Bengal and fluorescein in diagnosing keratitis?

It helps to visually differentiate between the edges and floor of epithelial defects. Signup and view all the answers

Which systemic treatment is recommended for managing stromal keratitis caused by herpes simplex virus?

Systemic antiherpetic medication such as Acyclovir tablets. Signup and view all the answers

What are the typical signs of keratitis observed during an eye examination?

Feathery borders and stromal infiltration. Signup and view all the answers

What are the main components of the cornea and their functions?

The cornea consists of the epithelium, Bowman's membrane, stroma, Descemet's membrane, and endothelium, providing a protective barrier, transparency, and structural integrity. Signup and view all the answers

How does the curvature of the cornea influence its refractive power?

The corneal curvature, which is 7.8 mm at the anterior surface and 6.5 mm at the posterior, determines its refractive power, contributing significantly to the eye's total optical power. Signup and view all the answers

What is the significance of the endothelial cell density in the cornea?

Endothelial cell density is vital for maintaining corneal hydration and transparency, with a normal count being above 500 cells/cm². Signup and view all the answers

Explain the role of Bowman's membrane in the cornea.

Bowman's membrane acts as a barrier that provides structural support to the cornea but does not regenerate after injury. Signup and view all the answers

What occurs at the limbus regarding the transition of corneal tissues?

At the limbus, the corneal epithelium transitions into conjunctival epithelium, and the Bowman's membrane becomes conjunctival stroma. Signup and view all the answers

What are the primary nutritional sources for the cornea?

The cornea obtains nutrition from perilimbal blood vessels, aqueous humor, and the tear film. Signup and view all the answers

How can corneal thickness vary, and what are its average measurements?

The corneal thickness ranges from 500-550 microns at the center to 500-900 microns at the periphery. Signup and view all the answers

Which conditions can lead to decreased or lost corneal sensations?

Conditions such as infections (e.g., herpes, syphilis, leprosy), trauma, and post-operative complications can lead to decreased corneal sensations. Signup and view all the answers

Describe the role of Descemet's membrane in the cornea.

Descemet's membrane serves as the basement membrane for the endothelial layer, providing structural support and a barrier to fluid ingress. Signup and view all the answers

Explain the term 'corneal pannus' and its relevance to corneal vascularization.

Corneal pannus refers to the ingrowth of vascular tissue into the cornea, often due to inflammation or chronic irritation. Signup and view all the answers

What is measured by corneal tomography (Pentacam)?

Corneal tomography measures corneal power maps, thickness maps, and elevation maps. Signup and view all the answers

What are the implications of corneal topography in clinical practice?

Corneal topography is used to measure the corneal power at different points, aiding in diagnosing and managing refractive errors. Signup and view all the answers

Identify the significance of corneal transparency for the functioning of the eye.

Corneal transparency is crucial as it allows light to enter the eye without obstruction, aiding in vision. Signup and view all the answers

What role does the Cochet Bonnet aesthesiometer play in ophthalmology?

The Cochet Bonnet aesthesiometer is used to assess corneal sensitivity by evaluating the reflex response to corneal touch. Signup and view all the answers

List the factors that contribute to maintaining corneal transparency.

Key factors include the avascular nature of the cornea, uniformity of collagen bundles, and integrity of the endothelium. Signup and view all the answers

Describe what a 'nebulous' opacity is in relation to the cornea.

A 'nebulous' opacity refers to a faint opacity in the cornea through which the iris structure can still be seen. Signup and view all the answers

What symptom indicates irritation due to spasm of the constrictor pupillae muscle?

Photophobia. Signup and view all the answers

What pathological change occurs to the anterior chamber after corneal perforation?

The anterior chamber collapses due to aqueous gush. Signup and view all the answers

Identify one common sign of corneal perforation.

+ve Fluorescein staining. Signup and view all the answers

What is a common treatment used to prevent synechia in acute corneal conditions?

Mydriatics. Signup and view all the answers

How does the cornea appear before perforation compared to after perforation?

Before: Corneal opacity; After: Central small or large perforation. Signup and view all the answers

What is one possible consequence of severe ciliary muscle spasm due to irritation?

Pain. Signup and view all the answers

Mention one complication that can arise after corneal perforation.

Total iris prolapse. Signup and view all the answers

What is the role of vitamins A and C in the management of corneal issues?

They promote healing and improve corneal nutrition. Signup and view all the answers

What are the two main types of corneal opacity mentioned?

Peripheral and central corneal opacity. Signup and view all the answers

Identify one cosmetic and one surgical approach to managing peripheral corneal opacity.

Cosmetic approach: Colored contact lens; Surgical approach: Glasses. Signup and view all the answers

Which infections are most commonly associated with bacterial corneal ulcers?

Pneumococci for typical ulcers and staphylococci or pseudomonas for atypical ulcers. Signup and view all the answers

What type of corneal ulcer is characterized by the presence of pus in the anterior chamber?

Bacterial corneal ulcer. Signup and view all the answers

What is the most common organism linked to infections caused by contact lens usage?

Pseudomonas. Signup and view all the answers

Name one non-infective cause of corneal opacity.

Neuropathic keratopathy. Signup and view all the answers

List two risk factors that can contribute to the development of corneal ulcers.

Corneal abrasion/trauma and dryness (xerosis). Signup and view all the answers

What surgical procedure is performed on superficial central corneal opacity?

PTK (Phototherapeutic keratectomy). Signup and view all the answers

Study Notes

Cornea Anatomy and Histology

Definition: The cornea is the transparent anterior 1/6 of the outer coat of the eye. The limbus is the junction between the cornea and sclera.
Epithelium: Non-keratinized stratified squamous epithelium, covered by a tear film. It regenerates rapidly.
Bowman's Membrane: A condensed superficial layer of the stroma. It does not regenerate.
Stroma: Comprising 90% of corneal thickness, it has uniformly spaced collagen fibers. Scarring rather than regeneration occurs. Recent surgical tissue is different from that found anatomically.
Dua (Pre-Descemet's membrane): Recent term for a surgical tissue rather than an anatomical structure.
Descemet's Membrane: The basement membrane of the endothelium.
Endothelium: A single layer of polygonal cells that do not regenerate upon damage.

Corneal Function and Refraction

Refraction and Power: The cornea is the main refractive media in the eye (power 42 diopters). Its power depends on corneal curvature (anterior surface ~7.8mm & posterior ~6.5mm) and refractive index (1.33).
Measurement: Corneal power can be measured using a keratometer (power and axis of the steepest and flattest meridians) or corneal topography (power at each point).
Corneal Thickness: Measured using ultrasound pachymetry or corneal tomography (e.g., Pentacam). Varies between 0.5-0.9mm at center and periphery.
Nutrition: Corneal is avascular. Nutrition is provided by perilimbal vessels, aqueous humor, and tear film..

Corneal Sensitivity and Sensations

Corneal Sensitivity Test: Tested using Cochet Bonnet aesthesiometer
Corneal Vascularization and Causes: Cornea has no blood vessels. Causes are infection, chemical injury, autoimmune diseases, corneal hypersensitivity, corneal pannus, post-corneal transplantation, post-traumatic, and extended use of contact lenses.
Decreased/Lost Corneal Sensations: Factors are infections (herpes, syphilis, leprosy), trauma, post-operative, post-irradiation, and compression of orbital structures (e.g tumors like orbital apex syndrome, superior orbital fissure syndrome).

Corneal Opacity and Treatment

Corneal Transparency Factors: Factors important for transparency include avascularity, non-myelinated nerves, uniformity of collagen bundles, non-keratinized epithelium, and integrity of the endothelium.
Types & Causes of Opacity: Corneal opacities can result from inflammation (keratitis), degeneration, dystrophies (corneal ectasia), edema, pigmentation, or pannus formation. Other causes described are: nebula, macula, leucoma, and keratectasia
Treatment for opacity: Cosmetic treatments (colored contact lenses, tattoos, glasses) and surgical treatments are described. Peripheral treatment: colored contact lens, tattooing, astigmatism correction, glasses, or contact lenses. Central treatment: Phototherapeutic keratectomy (PTK), deep anterior lamellar keratoplasty (DALK), and penetrating keratoplasty (PKP)

Keratitis (Corneal Ulcers)

Infective & Non-Infective Causes: Infective causes include bacterial (hypopion), fungal (mycotic), viral (herpetic), and protozoal (acanthamoeba). Non-infective causes include: marginal catarrhal ulcers, exposure keratitis, traumatic, neuropathic keratopathy, keratomalacia, and atheromatous ulcers.
Hypopion Corneal Ulcer: Pus in anterior chamber (usually bacterial in origin but may be sterile). Typical cases (70–80%) are caused by pneumococci, atypical by staphylococci, or other pathogens. Chronic dacryocystitis is a key predisposing factor.
Key Risk Factors: Corneal abrasion/trauma (most important) , dryness (xerosis), exposure, loss of sensation, long-term steroid use, contact lens use, poor hygiene.
Complications of Corneal Ulcer: Sudden decreased intraocular pressure (IOP), pain, and improved corneal nutrition can be caused by perforation. Other complications described are corneal opacity and vascularization, toxic iridocyclitis, secondary glaucoma, descemetocele/keratocele.

Viral Corneal Conditions

Herpetic Keratitis: Self-limiting condition where the virus is latent in the trigeminal ganglion. Can lead to primary, recurrent (dendritic, stromal, endothelial, geographic type) and disciform types
VZV Keratitis: Associated with Chickenpox and shingles. Symptoms can include: dermatitis, epithelial/stromal keratitis, scleritis, episcleritis, iridocyclitis, chorioretinitis, or optic neuritis.
Acanthamoeba Keratitis: Related to contact lens use/swimming pools. Characterized by severe pain, dendritic-like peripheral perineural infiltrates ("ring ulcers").

Treatments for Corneal Ulcers

General Treatment Approach: Corneal scrap with sensitivity, immediate broad spectrum antibiotic, mydriatic (prevents synechia, cycloplegic), eye protection, with vitamins (A&C) & lubricants.
Steroids & Topical Anaesthetics: These are discouraged
Specific Treatments: Anti-herpetic (acyclovir or gancyclovir), anti-fungal (e.g., natamycin, voriconazole), systemic antiherpetics, topical antibiotics, cycloplegics, lubricants, and (in severe cases) keratoplasty are used.

Other information

Symptoms: Pain, lacrimation, photophobia, blepharospasm, haloes around light, and blurring of vision are all described. Lid edema, ciliary injection (circumcorneal ciliary flush), corneal ulceration, and anterior chamber reaction are also described. Pupillary constriction (miosis) and fluorescein staining are diagnostic signs (inferred).

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