Abstract
Abstract: :
Purpose: Age–related macular degeneration is a leading cause of vision loss for people over the age of 50 in the Western world. For the early diagnosis of such functional disorders, an objective and simple method for measuring macular function is necessary. We have applied the technique of optical imaging of intrinsic signals to macaque retina, to establish a non–invasive imaging method that reveals two–dimensional functional organization of retina with fine spatial resolution. Methods: We have built an intrinsic signal imaging system for retina with which we can monitor reflectance changes in macaque under anesthesia (ARVO 2003). The intrinsic signals evoked by full field white flash stimulus (duration, 1 ms) was calculated by dividing the averaged images obtained after stimulus by those obtained during a 1–second period before the stimulus onset. Results: Under infrared illumination (800–950nm), decreases in light reflectance was observed over the whole posterior region of retina following a flash stimulus. The spatial patterns of signal intensity corresponded to anatomical cone distribution, with a peak of light absorption increase at the fovea. A functional map could be obtained even from a single imaging trial lasting only a few seconds. The optical signal intensity showed a statistically significant positive correlation with electrophysiological cone responses measured by multifocal electroretinogram. A focal lesion artificially induced by laser photocoagulation was identified as a region with low optical signal intensity. Furthermore, imaging under visible light (650nm) could detect not only decreases but increases in light reflectance, which may reflect bleaching of cone photopigment. Conclusions: We have successfully measured the intrinsic signals of retina, which reflected photoreceptor function in normal and artificially damaged eyes. This seems to be a promising method which will provide valuable information about the macular and peri–macular function in various disorders such as age–related macular degeneration, retinal artery– or vein–occlusion and retinitis pigmentosa.
Keywords: retina • topography • macula/fovea