Cornea and External Disease Flashcards

A 25-year-old patient with progressive myopic astigmatism is examined. On downgaze, the lower eyelid is pushed forward into a 'V' shape by the conical cornea. What is this clinical sign called?

Answer: Munson's sign

Munson's sign is the V-shaped indentation of the lower eyelid on downgaze, caused by an advanced conical cornea in keratoconus. It is a classic clinical sign indicating significant corneal ectasia.

A patient presents with a red, painful eye and foreign body sensation. Slit-lamp examination after fluorescein staining reveals a linear, branching epithelial lesion. This finding is pathognomonic for which condition?

Answer: Herpes simplex keratitis

A dendritic ulcer, which appears as a branching, tree-like lesion with terminal bulbs that stain with fluorescein, is the classic presentation of epithelial herpes simplex keratitis. It represents active viral replication within the corneal epithelium.

A 60-year-old female complains of blurry vision that is worse in the morning. Slit-lamp examination reveals corneal guttae and stromal edema. The primary pathology in this condition involves which corneal layer?

Answer: Endothelium

Fuchs' endothelial dystrophy is characterized by the progressive loss of corneal endothelial cells. This leads to the formation of guttae (excrescences on Descemet's membrane) and a breakdown of the endothelial pump function, resulting in corneal stromal and epithelial edema.

A 22-year-old who sleeps in their soft contact lenses presents with severe eye pain, discharge, and a corneal infiltrate with an overlying epithelial defect. Which organism is most notoriously associated with this clinical scenario?

Answer: Pseudomonas aeruginosa

Pseudomonas aeruginosa is a gram-negative bacterium commonly associated with contact lens-related infectious keratitis, particularly with overnight wear. It can be highly virulent, causing rapid corneal destruction and perforation if not treated aggressively.

A patient with Fuchs' dystrophy and significant corneal edema but a clear stroma is a candidate for a corneal transplant. Which procedure would be most appropriate to selectively replace the diseased tissue?

Answer: Descemet's Membrane Endothelial Keratoplasty (DMEK)

Descemet's Membrane Endothelial Keratoplasty (DMEK) is a type of partial-thickness corneal transplant that replaces only the patient's diseased endothelium and Descemet's membrane. It is the preferred procedure for isolated endothelial dysfunction like Fuchs' dystrophy as it offers faster visual recovery and lower rejection rates compared to full-thickness transplants.

A patient with dry eye disease has rapid tear break-up time but normal Schirmer's test results. Examination reveals inspissated meibomian glands. This presentation is most consistent with which type of dry eye?

Answer: Evaporative dry eye

This patient has evaporative dry eye, most commonly caused by meibomian gland dysfunction (MGD). The glands produce a deficient lipid layer for the tear film, leading to rapid evaporation and instability (short tear break-up time), even if the aqueous production (measured by Schirmer's) is normal.

A 50-year-old outdoor worker presents with a fleshy, triangular growth extending from the nasal conjunctiva onto the cornea. What is the most likely diagnosis?

Answer: Pterygium

A pterygium is a fibrovascular growth of the conjunctiva that crosses the limbus and encroaches onto the cornea, often in a triangular shape. It is strongly associated with chronic ultraviolet light exposure. A pinguecula, in contrast, is a degenerative lesion that is confined to the conjunctiva and does not cross onto the cornea.