A 70-year-old man using an eye drop reports eyelash growth and a change in eye colour. Which anti-glaucoma medication could be responsible?

• A. Timolol
• B. Dorzolamide
• C. Brimonidine
• D. Latanoprost

Answer: (D)

Prostaglandin analogs used for glaucoma work by increasing outflow of aqueous humor through the uveoscleral pathway. A common and distinctive side effect of these drugs is pigment changes around the eye and eyelash changes. Specifically, they can cause darkening of the iris and increased eyelash growth (hypertrichosis) due to stimulation of pigment production and hair follicles.

Latanoprost is a prostaglandin F2α analogue, so this combination of eyelash thickening and iris darkening points to it as the culprit. Other anti-glaucoma drugs (such as beta-blockers, carbonic anhydrase inhibitors, or alpha-2 agonists) have different side effect profiles and do not typically produce iris pigmentation changes or noticeable eyelash growth.