Single Cell Imaging of the Chick Retina with Adaptive Optics

Abstract

Purpose: The chick eye is extensively used as a model in the study of myopia and its progression; however, analysis of the photoreceptor mosaic has required the use of excised retina due to the uncorrected optical aberrations in the lens and cornea. This study implemented high resolution adaptive optics (AO) retinal imaging to visualize the chick cone mosaic in vivo.

Methods: The New England College of Optometry (NECO) AO fundus camera was modified to allow high resolution in vivo imaging on two 6-week-old White Leghorn chicks (Gallus gallus domesticus)–labeled chick A and chick B. Multiple, adjacent images, each with a 2.5^o field of view, were taken and subsequently montaged together. This process was repeated at varying retinal locations measured from the tip of the pecten. Automated software was used to determine the cone spacing and density at each location. Voronoi analysis was applied to determine the packing arrangement of the cones.

Results: In both chicks, cone photoreceptors were clearly visible at all retinal locations imaged. Cone densities measured at 36^o nasal-12^o superior retina from the pecten tip for chick A and 40^o nasal-12^o superior retina for chick B were 21,714 ± 543 and 26,105 ± 653 cones/mm² respectively. For chick B, a further 11 locations immediately surrounding the pecten were imaged, with cone densities ranging from 20,980 ± 524 to 25,148 ± 629 cones/mm².

Conclusion: In vivo analysis of the cone density and its packing characteristics are now possible in the chick eye through AO imaging, which has important implications for future studies of myopia and ocular disease research.

Keywords::

• Adaptive optics
• Cone
• Photoreceptors
• Retinal imaging
• Chick

ACKNOWLEDGMENTS

This study was supported by a National Eye Institute T35 summer research training grant (NIH-EY007149). The authors thank Kenneth Chung, Heather Melanson, and Joyce Wei for the imaging assistance as well as Rachel Currin, Oesa Eng, and Maria Walker for Matlab analysis of the images. We would like to thank Kristen Totonelly for assistance and training with ultrasound and refraction. Also, we are grateful to Dr Francis Rucker (New England College of Optometry) for advice and direction with chick modeling and Dr Joseph Corbo (Washington University, School of Medicine, St Louis) for useful discussion.

Declaration of interest: N. Doble was a founder of Iris AO Inc, the DM manufacturer. The other authors report no conflict of interest.