Visual field defects in ocular hypertension and glaucoma
D. Neima, R. LeBlanc and D. Regan
We measured visual fields using three unconventional test stimuli;
sine-wave 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.
