Topography of retinal damage in light-exposed albino rats

Previous studies have shown that retinal damage induced by damaging light exposure is more severe in superior retina than inferior retina when measured along the vertical meridian of eyes. However, the extent of retinal damage over all retinal regions is not clear. Albino rats were exposed to bright light (5000 lux for 6h) and eyes removed 7 days later. Outer nuclear layer (ONL) thickness was measured along four different meridians; temporal-to-nasal (T-N), superior-to-inferior (S-I), superiotemporal-to-inferionasal (ST-IN), and superionasal-to-inferiotemporal (SN-IT). As reported previously, superior retina is more severely damaged than inferior retina along the S-I meridian. In addition, we found that the temporal retina is more severely damaged than nasal retina on the T-N meridian. Color-coded topographic maps clearly revealed that thinning of ONL was greatest at 1-1.5mm superior and superiotemporal to the optic nerve head and that most damage was in the superiotemporal region of the fundus. For consistency in quantification of ONL thickness, using retinal sections cut along the S-I meridian is preferable to using those along the T-N meridian, since minor orientations to superior or inferior directions along the T-N meridian may cause greater variations in measured ONL thickness values in this experimental model.