Figure 1.

Light micrographs of central retinas of wild-type and arrestin/rhodopsin kinase double-knockout mice that were exposed to 200 ft-c white fluorescent light for various time. (a) Retina from double-knockout mice raised in the dark shows normal morphology. (b) Five hours after light exposure, mutant retina shows no signs of damage. (c) Eight hours after light exposure, overall retinal structure of mutant mice is preserved; however, early signs of apoptosis, such as condensed cytoplasm of rod inner segments (RIS) and scattered pyknotic nuclei in the ONL can be found. (d) By 16 h of light exposure, both the rod outer segment (ROS) and the rod inner segment are disorganized, and pyknotic nuclei are abundant in the ONL in mutant mice. However, the ONL still contains about 9–10 rows of nuclei as the normal morphology. Continuous exposure of mutant mice to light for 24 h (e), 48 h (f), and 96 h (g) begins to shorten the ONL, which has less than half of the initial number of nuclei left by 96 h. In contrast, the retina of wild-type mice that are exposed to the same light condition for 96 h (h) shows no signs of damage compared with the retina before light exposure (i). (Scale bar, 30 μm.)