The Effect of Refractive Correction on Automated Perimetric Thresholds

We determined the effect of introducing errors in refractive correction on the threshold retinal sensitivity in the central 6 degrees of the visual field in 11 normal subjects using automated static perimetry (Octopus program 62). A summated value of threshold retinal sensitivity was computed for each visual field by taking the sum of all 21 measured points in units of decibels. In 21 of 22 tested eyes, the emmetropic condition was associated with the highest summated retinal sensitivity. Summated retinal sensitivity decreased with increasing plus spherical (+1.00 and +2.00 diopters) power in 21 of 22 eyes. Threshold retinal sensitivity decreased -0.377 dB/degree for each degree away from fixation (P less than .0001). These slopes did not appear to depend on the refractive error (P = .77). Thus, even small refractive errors can artifactitiously decrease threshold retinal sensitivity within the central 6 degrees of the visual field.