In vivo measurements of cone photoreceptor density in normal human eyes based on images obtained with an adaptive optics imaging system (MICRO/ZSC-1)

Objective To study a practical application in clinical ophthalmology studies by measuring cone photoreceptor density from processed images obtained with an adaptive optics imaging system.Methods This was a cross-sectional study.An adaptive optics imaging system was used to image the cones of 30 normal human eyes and the position of each cone within the sampling windows was manually digitized by the investigator.From these cone counts,the density of the cones was calculated for a set of fixed distances from the fovea at locations throughout the image,and the images were processed to obtain the cone photoreceptor density in different regions (nasal and temporal sides, superior and inferior sides).A regression analysis was used to estimate the cone photoreceptor density in different regions. Results Cone photoreceptor densities decreased from 70 000 cells/mm2 to 16 000 cells/mm2 from a retinal eccentricity of 0.5°to 3°.Overall, cell densities showed a tendency to decrease with deviation from the fovea. Conclusion Clear high-resolution retinal images from human eyes in vivo can be obtained with an adaptive optics imaging system.This system may play a role in ophthalmology based clinical trials. Key words: Cones (retina);  Cell count;  Image processing,computer-assisted;  Optics system,adaptive