Visual Field Defects in Ocular Hypertension and Glaucoma

We measured visual fields using three unconventional test stimuli; sinewave grating targets of 2 and 5 cycles/ degree and a visual acuity target. Of 15 patients with ocular hypertension (OHT), eight had visual field defects for contrast sensitivity when tested with a sine-wave grating target of low spatial frequency; these patients had normal perimetric fields and normal fields for visual acuity. We hypothesize that the outer extremities of the largest dendritic trees of retinal ganglion cells become functionally ineffective in some patients with OHT and early glaucoma, possibly due to retinal ischemia, and as a result visual sensitivity to low spatial frequency gratings is reduced while visual acuity is spared. Since this hypothetical mechanism may be somewhat independent of the mechanism that causes ganglion cell loss, not all the contrast field defects in OHT would be expected to progress to glaucomatous field defects and be evident to clinical perimetry.