Reversibility by timolol of optic nerve disc cupping and pallor in ocular hypertensives (summary)

Abstract

study that focused on the effect of timolol on the optic disc in patients with ocular hypertension (OHT). Our investigation was concerned with the effect of timolol on optic disc cupping, as determined by photogrammetry, and pallor, evaluated by computerized image analysis.6s Cupping is a three-dimensional depression of the surface of the optic disc .4 Pallor is an important monitoring factor because of its relationship to visual field 10~s.~ Pallor also provides some indication of blood flow to the optic disc. Patients with OHT entered into this study had to have had ocular pressures ~21 mm Hg on two or more occasions without evidence of glaucomatous visual field loss. The timolol and placebo groups were matched for sex, race, iris color, intraocular pressure (IOP), blood pressure, and pulse rate. Forty-one patients meeting the criteria were randomly assigned to receive either timololO.5% or placebo drops in both eyes twice a day for 18 months. After a baseline examination, patients were observed at three-month intervals and photographs obtained for the measurement of cupping by photogrammetry11-18 and the measurement of optic disc pallor by computerized image with multiple plan points.‘” Visual fields were evaluated every six months with the Goldmann perimeter. There were progressive dropouts of individuals throughout the trial. Lack of compliance was the most frequent reason for discontinuance, although bradycardia occurred in some timolol-treated subjects. Patients with a pulse rate 160/min were dropped as a precaution. Our preliminary analysis using linear regression analysislO of all measurements of disc cupping as a function of time, irrespective of follow-up time, showed significant decreases in cup volume, with the timolol-treated eyes having a greater decrease than the placebo-treated eyes. When these data were expressed on a per-year basis, there was about a 15% net decrease in initial cup volume with timolol therapy* Similar analysis of the data obtained for disc pallor provided different results. Net average pallor decreased with timolol therapy about 8% for the right eye and 0.5% for the left eye. These changes were small, but only just statistically significant for the right eye. These results have to be confirmed by further analyses and studies, but it appears on preliminary analysis that timolol had a continuous effect on reversal of optic disc cupping for both eyes and pallor for the right eye.9 These changes are of interest, because in treating patients with OHT we were, in effect, probably intervening early in the disease and obtaining some reversal of disc parameters.