Psychophysical characterisation of early functional loss in glaucoma and ocular hypertension.
OBJECTIVE
The psychophysical evaluation of selective cell loss in early glaucoma and ocular hypertension.


METHODS
Contrast sensitivity was measured for the detection of luminance modulated gratings at a range of spatial (0.5, 2, 8 c/deg) and temporal (0, 16 Hz) frequency combinations in three groups of age matched patients (primary open angle glaucoma, ocular hypertension, normal controls; n=16). Stimuli of 5 degrees were presented foveally and at 15 degrees along the nasal horizontal meridian under photopic conditions.


RESULTS
Fovea: Compared to the normal group, the thresholds for the glaucoma patients were significantly elevated at all spatial and temporal frequencies (p<0.0001), but this reduction was not significantly different at any particular spatial or temporal frequency (p>0.1). There was no difference in contrast sensitivity between the normals and OHTs (p>0.10). Periphery: The thresholds of the glaucoma patients were elevated compared to the normal controls (p<0.01). The loss of sensitivity was slightly greater at the higher spatial frequencies for both stationary and flickering patterns but this did not reach significance (p=0.09). The contrast sensitivity in normal and OHT groups was not significantly different (p>0.10).


CONCLUSIONS
In early glaucoma, the reduction in contrast sensitivity to stimuli which isolate the magnocellular pathway (0.5 c/deg, 16 Hz) was not significantly different compared with the reduction in contrast sensitivity to stimuli that isolate the parvocellular pathway. These findings are not consistent with the hypothesis that the magnocellular pathway is selectively damaged in early glaucoma.
Ansari
E A
EA
Department of Ophthalmology, University of Wales College of Medicine, Cardiff, UK.
Morgan
J E
JE
Snowden
R J
RJ
D000328:Adult; D000368:Aged; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D005584:Fovea Centralis / Q000503:physiopathology; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000503:physiopathology*; D012684:Sensory Thresholds / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*