Effect of uncorrected refractive errors upon central visual field testing.

An investigation of the effects of uncorrected refractive errors upon a central visual field examination has been made with a view to establishing what the likely effects would be of omitting a refractive correction when screening the visual field with a threshold related, supra-threshold strategy on the Henson CFA3000. The results indicate that, while a linear relationship exists between the extent of threshold elevation and the product of residual refractive error and pupil size, the scatter in the results means that accurate predictions cannot be made in individual cases. The threshold elevation was found to be independent of eccentricity (within the central 21 degrees from fixation) and did not increase the variability of results. These last two findings indicate that uncorrected refractive errors are unlikely to affect the sensitivity of the threshold related, supra-threshold strategy to localized visual field defects.