To examine the histopathologic features of iridectomy specimens frompatients undergoing glaucoma surgery and to compare histologic abnormalitiesin a group of patients with a history of latanoprost therapy with those ina group of patients who had no history of prostaglandin therapy (controls).
Iridectomy specimens and patient history forms were submitted to thecentral Latanoprost Pathology Center. These were independently examined by3 ophthalmic pathologists in a masked fashion. Specimens were evaluated formalignant, premalignant, and other changes including differences in levelsof pigmentation, degrees of cellularity, inflammation, vascular abnormalities,and changes in the iris pigment epithelium.
Specimens were received from 449 patients with a history of latanoprosttreatment and 142 patients who had no history of treatment with latanoprostor other prostaglandin analogues. No evidence of malignant or premalignantchanges was found. In latanoprost-treated irides, the prevalence of iris freckleswas higher (P = .001) than in control irides,as was the combined number of stromal fibroblasts and melanocytes (P<.001). In a subgroup of specimens received through June 2002,there was no significant difference in mean melanocyte counts (P=.35) obtained by immunohistochemical staining techniques betweenthe latanoprost-treated and control groups.
These findings support previous studies indicating that latanoprost-inducedeye color changes are due to an increased amount of melanin within the irisstromal melanocytes. The increased numbers of freckles may be a focal manifestationof this effect.