Changes in Spectral Acuity following Laser Irradiation

Abstract

Maximal visual acuity and normal color vision are closely associated with foveal receptor function. When the fovea is destroyed or altered by intense laser irradiation, severe and sometimes permanent losses in visual acuity ensue. In this paper we have shown that the threshold for long-term functional alterations in the fovea is determined not only by the wavelength and corneal exposure power of a laser flash but also by the types of performance criteria used to assess visual functioning. Chromatic acuity provides a much lower threshold for permanent alterations (Krypton — 6 mW; Argon — 3 mW) as opposed to achromatic targets (HeNe — 11 mW). Further, the use of chromatic acuity to assess post-exposure functioning can more accurately delineate the specific cone process most affected by the exposing source. The data from these studies also suggest that some relatively long-term (24 h) cumulative process within the retina is occurring which obviously will affect any threshold value determined.

Visual Functional Changes Associated With Low-level Light Effects

“…In experiments designed to measure the immediate effects of acuity loss from foveal exposure in awake task-oriented rhesus (Robbins et al 1973(Robbins et al , 1980Robbins and Zwick 1980;Graham et al 1971), thresholds for permanent change were far more consistent with histological criteria than for exposures made under anesthesia where several days elapsed before acuity could be remeasured in exposed eyes. At transition levels of exposure from temporary to permanent visual acuity loss, more than one exposure was required to produce a permanent loss in visual acuity.…”

“…In a series of experiments on awake task-oriented rhesus (Robbins et al 1973(Robbins et al , 1980Robbins and Zwick 1980), the transition exposure level for a brief foveal exposure was determined. At that level, where temporary acuity loss transitioned to more permanent visual acuity loss, successive exposure had a cumulative effect on acuity, lengthening recovery time until recovery completely failed.…”