Interferometric resolution determinations in the fovea and parafovea.

Abstract

Foveal and extrafoveal interferometric determinations of retinal resolution were made on two observers. Resolution fell with increasing decentration of fixation. For example, the two subjects exhibited retinal resolution ‘equivalent’ to Snellen 20/40 respectively at 6.3° and 3.75° from fixation. The test criterion was the ability to distinguish the vertical line (fringe) interferometric pattern formed on the retina. One must conclude that comparable interferometric determinations (resulting in equivalent resolution measurements) do not imply that a patient has central fixation. This finding means that we must use care when interpreting the results of such tests on patients. Of course, if test parameters are altered, or if media are hazy or cloudy, the result may be somewhat different.