Flicker sensitivity in treated ocular hypertension

Reductions in flicker sensitivity in ocular hypertension are thought to precede manifest glaucomatous damage, but the proportion of patients with ocular hypertension reported to have losses in flicker sensitivity (50-90%) is far out of step with the proportion of ocular hypertensive patients in whom clinically defined glaucoma will develop (5-30%). The authors examined the possibility that the flicker losses in some of these patients represent not early glaucomatous damage, but instead a transient influence of raised intraocular pressure (IOP) on an otherwise normal eye. Temporal contrast sensitivity was measured in 26 patients with ocular hypertension and in 22 patients with primary open-angle glaucoma (POAG) before and after hypotensive treatment (timolol). Compared with normotensive controls, all POAG patients exhibited sensitivity losses before treatment which remained unchanged after treatment. The ocular hypertensive patients were divided into three groups, which may reflect differing risks of glaucoma conversion. Group I patients (8/26) had normal flicker sensitivity, and thus appear to be resistant to high IOP. Group II patients (9/26) showed initial losses which disappeared with lowered IOP. They probably have not yet suffered damage but appear to be sensitive to high IOP. Group III patients (9/26) had losses that persisted despite lowered IOPs. The similarity of their response to that of the POAGs suggests that group III patients have already suffered early glaucomatous damage.