The effect of refractive blur on the visual field using the ring perimeter.
To determine the effect of optically induced blur on the visual field measured with high pass spatially filtered targets, 10 normal subjects had field examinations with 0 diopter + 1.00 diopter or + 2.00 diopter of overcorrection in the cyclopleged state. All subjects showed a significant loss of sensitivity when defocussed, but not with pupil dilation. Mean thresholds for the central field rose from 4.79 +/- 0.68 dB (Mean +/- SD) with the image focussed and pupil dilated, to 7.16 +/- 0.72 dB with two diopters of image blur (P less than 0.001). The effects of defocussing did not differ significantly between the central and peripheral parts of the field. The great influence of defocussing the image on sensitivity should be considered during clinical perimetry as the 2.37 dB decline shown would place the group's mean sensitivity below the fifth percentile for age corrected normals.
House
P H
PH
Department of Ophthalmology, University of British Columbia, Vancouver, Canada.
Drance
S M
SM
Schulzer
M
M
Wijsman
K
K
D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology; D003519:Cyclopentolate / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008297:Male; D011680:Pupil / Q000187:drug effects; D011897:Random Allocation; D012029:Refraction, Ocular; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields
D003519:Cyclopentolate