A standardized approach for iris color determination.

Abstract

Latanoprost, the phenyl-substituted prostaglandin F2alpha, has been found to be an effective agent for glaucoma therapy. This prostaglandin derivative exerts ocular hypotensive activity but is also associated with an untoward side effect, namely iris color changes. Latanoprost provoked iris color changes in cynomolgus monkeys and in multicenter clinical trials. Until now photographs were taken and compared with color plates to document these changes. The disadvantage of this method is obvious, i.e., the color luminance varies between measurements due to changes in the developer. Furthermore, subjective comparison of color changes relative to color plates rendered judgment subject to impression and opinion rather than to objective data. Therefore, a computerized method using a 3-CCD video camera attached to a slit lamp was developed. The signals were transferred to a computer and a single frame, which was "frozen" by means of a "grabber card." Camera and the computer had previously been calibrated and color plates were measured to check the standard conditions. They were evaluated by a software program displaying average color (as red, green, and blue values) of the selected area. This method provides a fast and accurate way to quantify color changes in the iris of both experimental animals and clinical trials.