正常和弱视者立体和形状视觉感知时间的差异

THE DIFFERENCE OF PERCEPTION TIMES ON STEREOPSIS AND FORM VISION BETWEEN NORMAL AND AMBLYOPIC SUBJECTS

在速示器,以随机点立体图对为刺激,测量了正常和弱视者的立体视和形状视感知时间。实验表明:正常被试需要大约100ms感知深度,110ms或更长时间感知形状。这二种感知时间与刺激视差的种类和大小无关。弱视者需要比正常人较长的时间达到立体和形状的视感知。这二种感知时间的差别,弱视者也大于正常人。视锐度和立体视范围均恢复到正常的弱视者,以上二种感知时间,可以达到正常人范围,也可能显著地大于正常人。

The perception times (PT) of stereopsis and form vision in normaland anisometropic amblyopic subjects were measured using StereoscopicTest Charts (S-M Yan, and Z-Y Zheng, 1985). These charts consist ofanaglyph (red-green) random dot stereograms (RDS) which have a rangeof zero (20-320 sec arc), and crossed, uncrossed (12-60 min arc) dispa-rities. The forms defined by stereoscopic disparity include common figuressuch as triangles, squares, etc. Tachistoscopic (Gl136, Gerbrands Corp.)presentations were used to control test stimulus and mask durations. Forboth normal and amblyopic subjects the perception of depth preceded theperception of form. For normal subjects about 100 ms were required toperceive depth while an additional 10 or more ms were needed to perceiveform. Stereopsis and form PT were independent of absolute disparity.Amblyopic subjects needed longer time for stereopsis and form perceptionscompared to normal subjects, The difference of PT between stereopsis andform in the amblyopic subjects was also longer than those of the normal. Two recovered amblyopes were also tested. The long term recoveredsubject had perception times within the normal range. Interestingly, therecent recovered patient who appeared clinically normal, still had eleva-ted perception times. This technique may prove to be a particularly sensi-tive measure of recovery from amblyopia beyond that of visual acuity.