What should patients understand about iris color changes with prostaglandin analog therapy?

• A. Iris color darkening may occur in both eyes and is always temporary.
• B. Iris color darkening may occur in the treated eye and can be permanent.
• C. Iris color remains unaffected by treatment.
• D. Iris color changes are systemic rather than localized.

Answer: (B)

Prostaglandin analogs used for lowering eye pressure can cause pigment changes in the iris because they stimulate melanin production in iris melanocytes. This effect is localized to the eye being treated, not a systemic change. The color change is usually gradual over months to years and may be permanent, often most noticeable in the treated eye, and it can occur even if only one eye is using the medication. If both eyes receive treatment, both can darken over time. So, patients should understand that iris darkening may occur in the treated eye and can be permanent, rather than being temporary or systemic.