Visual mode switching for glasses: Observers can learn to immediately correct spatial distortions produced by prescription lenses

Wearing prescription glasses often produces geometric distortions while improving focus. For instance, cylindrical lenses, prescribed for astigmatism, create skew by scaling the image along an oriented axis, causing rectangles to appear like slightly tilted parallelograms. Most people adapt to these distortions, and report the world returning to normal appearance after a few days. They additionally note normal appearance immediately when they put on the glasses back on, and when they take them off. However, there have been few laboratory tests of learned immediate adjustment to compensate for geometric distortions; here we examined whether observers can learn to rapidly switch to "glasses mode”. Five observers wore +1.25D, 45-deg axis, cylindrical lenses binocularly, which skewed and blurred the images reaching the eyes. They wore the lenses in glasses for four hours during each of five consecutive days. Perception of skew was measured using a cancellation method. Observers adjusted the physical skew (along the 45 degree axis) of a parallelogram presented against a grayscale naturalistic background. Observers set the physical skew so that it canceled the effects of the glasses, and the parallelogram appeared to contain 90 degree angles. When first donning the glasses on day 1, observers settings were around 2% on average (scaled by 1.02 along the -45 degree axis); this scaling counteracted the skew produced by the glasses, producing a perceived rectangle. By day 5, however, this initial setting reduced to an average of 1%, indicating that the world appeared much less skewed when putting the glasses on. This trend across days was visible in all individual observers and reliable at the group level (t(4) =-4.9859, p < 0.01). These results suggest that observers can learn to rapidly adjust their perception to counteract spectacles' distortions. Failure of such learning may underlie dissatisfaction with glasses, especially for more complex prescriptions.