Scotopic sensitivity loss in glaucoma
B. Drum, M. F. Armaly and W. Huppert
Photopic and scotopic increment thresholds were measured at selected visual
field positions for 39 patients suspected of having glaucoma, 39 patients
with diagnosed glaucoma, and 31 age-matched normal control subjects.
Stimuli were presented at equal-eccentricity pairs of positions just above
and below the nasal horizontal meridian. Both photopic and scotopic
thresholds were elevated significantly for both the suspect and glaucoma
groups. The average photopic and scotopic threshold elevations were the
same for the suspect group, but scotopic threshold elevations were
substantially greater than photopic threshold elevations for the glaucoma
group. In a more detailed analysis of the glaucoma group data, local and
diffuse components of the photopic and scotopic threshold elevations were
operationally defined. The analysis revealed that localized photopic and
scotopic scotomas were of equal depth, but diffuse scotopic defects
exceeded diffuse photopic defects by a factor of 2:1 log units. These
findings suggest that not all ganglion cell types are equally susceptible
to glaucomatous damage and also point to scotopic perimetry as a
potentially sensitive test for early glaucoma detection.
