After six months of unilateral latanoprost therapy for glaucoma, a brown-eyed patient notices that the treated iris has become visibly darker than the fellow eye. The mechanism responsible for this change is:

• A Deposition of drug pigment complex within iris stromal melanocytes
• B Stimulation of melanogenesis in iris melanocytes with increased melanin production ✓
• C Necrosis and phagocytosis of iris pigment epithelium releasing pigment into the stroma
• D Reactive hyperplasia of the iris dilator muscle fibres

Explanation

Prostaglandin analogues stimulate melanocytes through prostanoid receptors, increasing melanin synthesis within the iris stroma, so the change is gradual, irreversible, and confined to the treated eye. It is benign but cosmetically significant and must be warned about before starting therapy. Pigment dispersion into the aqueous (option C) describes pigmentary glaucoma physiology, not latanoprost-induced heterochromia. Hypertrichosis of lashes also occurs through growth-cycle stimulation of lash follicles.

Reference: Parsons' Diseases of the Eye, 22nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.