Nerve Fiber Layer Defects with Normal Visual Fields: Do Normal Optic Disc and Normal Visual Field Indicate Absence of Glaucomatous Abnormality?

Abstract

When the optic disc has normal appearance with no abnormalities in routine automated perimetry, the subject is not considered to have glaucoma. The purpose of this study is to show how such patients may have localized retinal nerve fiber layer defects with corresponding functional abnormality. The authors selected eight eyes of eight patients who had a localized retinal nerve fiber layer defect extending within a few degrees from fovea but in whom the optic disc appearance and Humphrey 30-2 visual fields were normal. Of the eight patients, three had positive family history of glaucoma, two had suspected retinal nerve fiber layer abnormality in routine eye examination, two had increased intraocular pressure (IOP), and one had advanced low-tension glaucoma in one eye with a normal fellow eye. The authors examined the central 10 degrees visual field with 1 degree resolution using Humphrey perimeter and the Ring and Centring programs of the high-pass resolution perimeter. A central field defect corresponding to retinal nerve fiber layer defect was found in six of eight patients: in both 10 degrees Humphrey field and Centring programs (2 eyes), in Humphrey only (2 eyes), and in Centring only (2 eyes). The results indicate that retinal nerve fiber layer photographs are helpful in diagnosing glaucoma because early glaucomatous abnormalities cannot be excluded without nerve fiber layer photography. Currently available routine perimetric examination programs do not always detect very early functional damage.