Reflected images of a white ring fr

Reflected images of a white ring from the fiber-optic ring illuminator of the stereoscopic zoom microscope (SMZ 1500; Nikon) were taken immediately after euthanasia, 2 hours after instillation of the last treatment drop. This ring light is firmly attached and surrounds the bottom of the microscope objective. Because the illumination path is nearly coincident with the optical axis of the microscope, the viewing area is evenly illuminated and nearly shadowless. The projected ring light will reflect off a wet surface and the regularity of the reflected ring depends on the surface’s smoothness. The smoothness of the reflected rings was graded in digital images by two masked observers. The projected ring was divided into four quarters, of 3 clock hours each. The corneal irregularity severity score was calculated using a 5-point scale based on the number of distorted quarters in the reflected ring: 0, no distortion; 1, distortion in one quarter of the ring (3 clock hours); 2, distortion in two quarters (6 clock hours); 3, distortion in three quarters (9 clock hours); 4, distortion in all four quarters (12 clock hours); and 5, severe distortion, in which no ring could be recognized.