Abstract
Purpose:
To assess the cone packing density in emmetropic and myopic patients using adaptive optics and its correlation with retinal sensitivity.
Methods:
An adaptive optics retinal camera prototype (rtx1, Imagine Eyes) was used to evaluate the cone packing density. The rtx1 consists of a wavefront sensor (HASO 32-eye, Imagine Eyes), a correcting element (MIRAO 52-e, Imagine Eyes), and a high resolution charge-coupled device camera (Rope Scientific). T A light source of 850 nm is used to illuminate the retina and capture an image of 4 degree x 4 degree. Cone packing density analysis was performed using a custom software (Imagine Eyes). All images were processed by the software for cone analysis. A total of 25 emmetropic and 25 myopic subjects were analyzed. Five images , foveal (0°,0°), superior (3°,0°), inferior (0°,-3°), temporal (-3°,0°) and nasal (3°,0°) were acquired. Emmetropic subjects were studied for cone packing densities along with microperimetry to determine threshold sensitivity and fixation characteristics.
Results:
Cone packing densities were calculated at 2 degrees and 3 degrees from the fovea in the temporal , superior, nasal and inferior quadrants Mean cone packing densities in different quadrants were 25786.68+-4367.07 temporal , 23009.35+/-5415.81 , superior,22838.09+/-4166.22 nasal and 21097.53+/-4235.84 inferior. Mean cone packing densities at 2 degree from the fovea was 25154.67+-4777.69 and at 3 degreea was 21.366.28+-4167.86. The sensitivity values derived using MAIA at 2 degrees from fovea was 31.13dB and at 3 degrees was 30.43dB and the mean in each quadrant was temporaly 31.69 dB, superiorly 30.61dB, nasaly 31.15 dB and inferiorly was 29.67 dB.There was a significant correlation between the cone density and the retinal sensitivity in all the quadrants and with the eccentricies.
Conclusions:
As the cone density decreases with increasing distance from the fovea, the retinal sensitivity using microperimetry also decreases proprtionally. Hence structural cones can be considered functional cones. Understanding their distribution is of importance in diseased retina to consider newer theraopeutic modalities and monitoring their response to treatment .
Keywords: 648 photoreceptors •
688 retina •
605 myopia