Colour contrast sensitivity in ocular hypertension. A five-year prospective study.

Abstract

To evaluate a peripheral colour contrast sensitivity test as a tool for early diagnosis of glaucoma in a five-year prospective study. Peripheral colour contrast sensitivity was measured with a computer graphics system developed by Arden et al. The test colours were varied along the protan, deutan and tritan colour confusion axes on a scale from 0 to 100 percentage units. Fifty-five ocular hypertensive (OH) patients examined with the colour contrast test, stereoscopic photography of the optic discs, and measurements of visual fields (Humphrey 24-2 glaucoma hemifield test (GHT)) in 1994, were re-examined after five years. Ten patients were 'outside normal limits' in the GHT at follow-up. This group of 10 patients did not differ in colour contrast thresholds at the test in 1994 from the 45 who were still 'normal' (or 'borderline') at follow-up. Neither were there proportionally more patients with GHT 'outside normal values' for the patients with high colour contrast thresholds (> 30% units) in 1994 regarding any of the three colour axes. As judged from patient files, 27 patients had developed glaucoma during follow-up. Although there were differences between these 27 glaucoma patients and the remaining OH group at the colour contrast test in 1994, these differences did not reach statistical significance for any of the colour axes (largest difference in the tritan axis: 6.2% units, P = 0.0745). At follow-up, however, there was a significant difference in colour contrast for the protan axis between the clinical glaucoma group and the OH group (6.7% units, P = 0.0105). The method used for colour contrast measurement did not reveal glaucomatous changes before conventional perimetry (Humphrey 24-2, GHT). Neither did it predict the patients who, in our clinic, subsequently developed glaucoma during a five-year period. A change over time in colour contrast in the protan axis for an OH patient may, however, indicate glaucoma development.