A NOVEL SYSTEM FOR THE OBJECTIVE CLASSIFICATION OF IRIS COLOR AND ITSCORRELATION WITH RESPONSE TO 1-PERCENT TROPICAMIDE

Iris colour can provide an enormous amount of information about an ind ividual. In addition to changes with pathological conditions, the colo ur of the in's can be a particularly useful indicator of how well a pe rson will respond to a topically applied ocular drug. Until recently, classification of iris colour has been subjective, ranging from a basi c description ('light' and 'dark') to more detailed grading systems, s uch as a comparison with preset photographic standards. However, varia bility within observers and differences in the interpretation between observers can influence the results. Objective techniques, in this res pect, possess several advantages. They are able to detect differences in colour that subjective techniques are incapable of and they provide continuous data rather than discrete categories, thus improving the a ccuracy of drug response predictions. This study assessed iris colour by objective means. Slit-lamp photographs of Various coloured irides w ere taken under standardised conditions. The slides were then scanned into a computer and the colour analysed using a calibrated software pa ckage. To establish the optimum colour parameter to be used for predic tions of drug response, several parameters were calculated and compare d with the subject response to 1% tropicamide (maximum change in pupil size, time to maximum change and total duration of effect). Many para meters had strong correlations with drug response, but the parameters 'z', 'b' (the proportion of blue in the image) and 'y' (the proportion of yellow in the image) were found to exhibit the highest correlation s. They also showed better correlations with drug response than did a current iris colour grading system. (C) 1998 The College of Optometris ts. Published by Elsevier Science Ltd.