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OP4.1-10 | Cornea, Keratitis and Eye Donation — Graded Quiz
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A patient has five distinct corneal layers on slit-lamp optical section. Which layer is responsible for maintaining corneal hydration through active ionic pumping and is post-mitotic in adults?
Correct. The endothelium pumps fluid out of the stroma using Na/K-ATPase. It is post-mitotic — lost cells are not replaced. Critical endothelial cell density (below 500 cells/mm2) causes irreversible corneal decompensation.
The corneal endothelium maintains stromal deturgescence through Na/K-ATPase pumps. It is post-mitotic — cells lost to injury or disease are not replaced, making endothelial cell count the key determinant in keratoplasty candidacy and surgical risk.
Incorrect. Bowman's layer is a structural barrier; the stroma provides tensile strength; Descemet's membrane is the endothelial basement membrane. Only the endothelium performs active fluid pumping essential for transparency.
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A 16-year-old male presents with progressive myopia that is not correctable beyond 6/18. Slit-lamp shows inferior corneal thinning with oil-droplet reflex on retinoscopy. Fleischer ring is noted at the base of the cone. Corneal topography confirms irregular astigmatism. This is a congenital anomaly of which embryological origin?
Correct. Corneal stroma and endothelium derive from neural crest cells. Keratoconus involves failure of the neural-crest-derived stroma to maintain structural integrity. The Fleischer ring (iron deposition at cone base) and oil-droplet reflex are pathognomonic.
Keratoconus is a corneal stromal ectasia. The stroma derives from neural crest cells (as does the endothelium). The primary defect in keratoconus involves stromal collagen cross-linking failure and proteolytic degradation of neural-crest-derived stroma.
Incorrect. Surface ectoderm gives rise to the epithelium. Neuroectoderm gives the retina and uvea. Mesoderm contributes to extraocular muscles. The corneal stroma and endothelium are neural crest derivatives — relevant in keratoconus and Peters' anomaly.
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A 45-year-old woman presents with right eye pain, redness, and photophobia for 3 days. She has systemic lupus erythematosus on hydroxychloroquine. Slit-lamp: deep stromal infiltration with vascularisation, no epithelial defect. Corneal sensation is normal. What is the most likely diagnosis?
Correct. Interstitial keratitis presents as stromal inflammation with vascularisation and no epithelial ulcer. In the context of SLE, this is autoimmune IK. Bacterial and fungal keratitis require an epithelial breach as the portal of entry.
Interstitial keratitis involves the corneal stroma with vascularisation but NO epithelial defect. In adults, common causes include autoimmune disease (SLE, sarcoidosis, Cogan's syndrome). Syphilitic IK is a classic cause historically. The absence of an epithelial defect distinguishes IK from ulcerative keratitis.
Incorrect. Bacterial, fungal, and Acanthamoeba keratitis all require an epithelial defect. The key here is stromal involvement with neovascularisation and NO epithelial ulcer in a patient with a known autoimmune disease — this pattern defines interstitial keratitis.
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Match the organism to the CORRECT first-line drug. A contact-lens wearer develops a suppurative corneal ulcer with hypopyon, rapid progression in 24 hours, and a grey-white infiltrate with clear surroundings. Culture grows gram-negative rods. The correct treatment is:
Correct. Pseudomonas bacterial keratitis is treated with topical fluoroquinolone (ciprofloxacin 0.3%) or fortified tobramycin. This is organism-specific: gram-negative bacteria require antibiotics, NOT antifungals, antivirals, or anti-amoebics.
Rapid-onset suppurative ulcer in a contact lens wearer with gram-negative rods = Pseudomonas aeruginosa bacterial keratitis. Treatment: topical fluoroquinolone (ciprofloxacin 0.3%) or fortified aminoglycoside (tobramycin). Natamycin is for fungi; acyclovir for HSV; chlorhexidine/propamidine for Acanthamoeba.
Incorrect. This is the critical organism-to-drug matching question. Natamycin is for filamentous fungi; acyclovir is for HSV dendritic keratitis; chlorhexidine + propamidine is for Acanthamoeba. Gram-negative bacterial keratitis requires a fluoroquinolone or fortified antibiotic.
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A 60-year-old farmer presents with a dense white corneal opacity covering the visual axis. Through it, the iris cannot be seen. The opacity has been present since a perforated corneal ulcer healed 5 years ago with iris prolapse into the wound. Which type of opacity is this?
Correct. Adherent leukoma results from corneal perforation with iris prolapse — the iris becomes adherent to the posterior corneal surface. It is the densest and most complex corneal opacity, often associated with raised IOP due to angle distortion.
Adherent leukoma is a dense corneal opacity with iris tissue adherent to its posterior surface, resulting from a perforated corneal ulcer where the iris plugged the perforation. It represents the most severe form of corneal opacity and may cause secondary glaucoma.
Incorrect. Nebula is faint; macula is visible in direct light with iris visible through it; leukoma is dense with iris not visible. Adherent leukoma specifically results from iris adhesion to a corneal scar after perforation — distinguishing it from simple leukoma.
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A 55-year-old woman with meibomian gland dysfunction complains of worsening symptoms in the afternoon, improved after blinking. Schirmer I test is 18 mm. Tear break-up time is 4 seconds. The meibum is thick and turbid. The primary mechanism and first-line management are:
Correct. Normal Schirmer test with low TBUT and obstructive MGD indicates evaporative dry eye due to lipid layer instability. Warm compresses liquefy inspissated meibum; lid hygiene removes toxic stagnant lipid. This is the correct mechanism-matched first-line treatment.
Meibomian gland dysfunction causes evaporative dry eye due to lipid layer deficiency. Normal Schirmer test (18 mm) and short TBUT (4 s) with obstructive meibomian disease indicates evaporative DED. First-line: warm compresses and lid hygiene to liquefy and release inspissated meibum.
Incorrect. A normal Schirmer test (18 mm) rules out aqueous deficiency. The short TBUT with MGD points to evaporative mechanism (lipid layer instability). Punctal plugs are for aqueous-deficient DED; cyclosporine targets inflammation. Warm compresses and lid hygiene address the root cause.
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India's National Programme for Control of Blindness and Visual Impairment (NPCBVI) defines blindness as a presenting visual acuity of less than:
Correct. India's NPCBVI defines blindness as presenting VA less than 6/60 in the better eye — a different (more inclusive) threshold than WHO's less than 3/60. This broader definition is used for programme planning and resource allocation in India.
The WHO definition of blindness is presenting VA less than 3/60. India's NPCBVI uses a stricter operational definition of less than 6/60 to capture a wider population for programme eligibility. Students must know both thresholds.
Incorrect. While WHO sets blindness as less than 3/60, India's NPCBVI programme uses less than 6/60. This distinction is tested in community ophthalmology and national health programmes — both thresholds must be memorised.
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A 58-year-old woman with Fuchs' endothelial dystrophy has bilateral corneal oedema and specular microscopy showing 400 cells/mm2. Stroma is clear on anterior segment OCT. Which procedure is the CURRENT standard of care for this condition?
Correct. Fuchs' dystrophy is a primary endothelial disease. DMEK replaces only Descemet's membrane and endothelium (the diseased tissue), preserving all host stroma. It provides faster visual rehabilitation and lower rejection risk compared to penetrating keratoplasty or DSAEK.
Fuchs' endothelial dystrophy requires endothelial replacement. DMEK (Descemet membrane endothelial keratoplasty) is the current gold standard: it transplants only Descemet's membrane and endothelium, giving faster visual recovery, lower rejection rates, and better refractive outcomes than DSAEK or PK.
Incorrect. DALK replaces anterior stroma — inappropriate for an endothelial disease. Penetrating keratoplasty replaces all layers unnecessarily when stroma is healthy. Therapeutic contact lens does not treat endothelial failure. DMEK is the tissue-specific, minimally invasive standard of care.
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An eye bank receives a cornea from a 68-year-old donor who died of HIV infection. The eye bank's correct action is:
Correct. HIV is an absolute contraindication to eye donation for any purpose including research. The cornea must be discarded. Informed consent from the recipient does not override this — the risk of transmission is unacceptable.
Active HIV infection is an absolute contraindication to corneal donation for transplantation, research, or training. Other absolute contraindications include active Hepatitis B or C, rabies, prion diseases (CJD), septicaemia, intraocular malignancy, and unknown cause of death. The tissue must be discarded.
Incorrect. HIV infection is an absolute contraindication — the tissue cannot be used for transplantation or research. Re-testing after 3 months is not standard practice for a known HIV-positive donor. Discard is the only safe option.
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A patient presents with a rusty ring (rust ring) visible around a metallic corneal foreign body after removal of the metallic fragment. The appropriate management is:
Correct. Rust rings are iron oxide deposits that are toxic to the cornea and must be removed. However, waiting 24-48 hours after the metallic FB is removed allows the ring to soften, making the second sitting removal with an Alger brush safer and more complete.
A rust ring forms when a metallic foreign body oxidises in the corneal stroma. It is toxic to epithelium and must be removed, but immediate removal of a freshly formed rust ring is technically difficult and risks deeper injury. Allowing 24-48 hours softens the ring (aided by topical antibiotics preventing infection) and makes removal with an Alger brush or needle easier and safer.
Incorrect. Rust rings do not dissolve spontaneously — they cause progressive corneal toxicity and must be removed. Immediate aggressive removal risks deeper stromal injury. Keratoplasty is not indicated. The correct approach is to start topical antibiotics and remove the softened rust ring at a second sitting in 24-48 hours.
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