After eight months of unilateral latanoprost therapy for glaucoma, a patient reports that the treated eye appears darker-eyed than the fellow eye in the mirror. The most likely cause is:
- A Deposition of drug pigment complex in the iris stroma
- B Post-inflammatory hemosiderin staining of the iris
- C Increased melanin synthesis within iris melanocytes ✓
- D Pigment dispersion from reverse pupillary block
Correct answer: C. Increased melanin synthesis within iris melanocytes
Explanation
Latanoprost stimulates melanocytes in the iris stroma, increasing melanin production and causing gradual darkening of light-colored irides, typically after several months of therapy. The change is usually permanent and is more likely with unilateral treatment, producing heterochromia. It is not pigment deposition of the drug, not hemosiderin, and unrelated to pigment dispersion syndrome, although latanoprost can cause mild anterior chamber flare and should be used cautiously in uveitis and herpetic keratitis histories.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.