The photoreceptors of the retina represent the first step of vision. This project will use advanced adaptive optics imaging techniques to bypass the resolution limits imposed by the eye's optics in order to measure cellular structure and function in the living human retina. Using the techniques already developed in our lab we will be able to probe photoreceptors with unprecedented precision. In addition, we will further develop Adaptive Optics imaging techniques to improve our existing ability to image the rod and cone photoreceptors of the eye, with the goal of imaging every photoreceptor in large regions of the posterior pole in a single subject session. This will be achieved using dual wavelength imaging where we use near infrared light to image the cones at high contrast, and use simultaneously acquired low intensities visible light images to provide higher resolution images of rods and cones through image averaging. The ability to use visible light at lower intensities will also allow us to directly measure the amount of photopigment in the eye, and how the quantity of photopigment changes with bleaching and regeneration. Finally, by using the high quality images to dynamically guide a retinal tracking algorithm, we will probe local retinal sensitivity over abnormal regions of the eye using a dual image stabilization technique and probing retinal sensitivity on a purely local basis. We will use the above techniques to ask a specific series of questions. These questions focus on the control of retinal light absorption, and the effects of aging and disease on the ability of the photoreceptors to collect light. The first question addresses how photoreceptor packing interacts with the amount of photopigment in the outer segments to set the relative absorptivity of cones. If cones actively control their quantum catch, then individuals with larger cones in a given area could be expected to have lower optical density of their pigment. Similarly as the eye ages, there should be adjustments in the photopigments that reflect losses in photoreceptor numbers. In the second set of experiments we will extend this analysis to patients with early age related maculopathy and early geographic atrophy testing the nature and extent of photoreceptor changes. In a final set of experiments we will pursue preliminary data showing that cones have a common phenotypic appearance across a number of early stage diseases. We will test the hypothesis that cones that are diseased, but not yet dead, have a common functional and structural appearance. If true, it would imply that this change could be an effective biomarker of a retina at risk for vision loss and for treatment efficacy.

Public Health Relevance

To fully understand the impact of new therapies, as well as to monitor treatments, we need to develop better ways to monitor the health of the living human retina. We will further develop our proven technology for imaging the retina at cellular resolution in order to provide full spatial maps of rod and cone photoreceptors as well as to estimate their photopigment content. We will apply these techniques to better understand the impact of aging and retinal disease on human photoreceptors.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Special Emphasis Panel (ZRG1-BDPE-J (09))
Program Officer
Neuhold, Lisa
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Indiana University Bloomington
Schools of Optometry/Ophthalmol
United States
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Huang, Gang; Gast, Thomas J; Burns, Stephen A (2014) In vivo adaptive optics imaging of the temporal raphe and its relationship to the optic disc and fovea in the human retina. Invest Ophthalmol Vis Sci 55:5952-61
Chui, Toco Y P; VanNasdale, Dean A; Elsner, Ann E et al. (2014) The association between the foveal avascular zone and retinal thickness. Invest Ophthalmol Vis Sci 55:6870-7
Burns, Stephen A; Elsner, Ann E; Chui, Toco Y et al. (2014) In vivo adaptive optics microvascular imaging in diabetic patients without clinically severe diabetic retinopathy. Biomed Opt Express 5:961-74
Chui, Toco Y P; Gast, Thomas J; Burns, Stephen A (2013) Imaging of vascular wall fine structure in the human retina using adaptive optics scanning laser ophthalmoscopy. Invest Ophthalmol Vis Sci 54:7115-24
Chui, Toco Y P; Zhong, Zhangyi; Song, Hongxin et al. (2012) Foveal avascular zone and its relationship to foveal pit shape. Optom Vis Sci 89:602-10
Huang, Gang; Qi, Xiaofeng; Chui, Toco Y P et al. (2012) A clinical planning module for adaptive optics SLO imaging. Optom Vis Sci 89:593-601
Zou, Weiyao; Burns, Stephen A (2012) Testing of Lagrange multiplier damped least-squares control algorithm for woofer-tweeter adaptive optics. Appl Opt 51:1198-208
Huang, Gang; Zhong, Zhangyi; Zou, Weiyao et al. (2011) Lucky averaging: quality improvement of adaptive optics scanning laser ophthalmoscope images. Opt Lett 36:3786-8
Song, Hongxin; Chui, Toco Yuen Ping; Zhong, Zhangyi et al. (2011) Variation of cone photoreceptor packing density with retinal eccentricity and age. Invest Ophthalmol Vis Sci 52:7376-84
Zhong, Zhangyi; Song, Hongxin; Chui, Toco Yuen Ping et al. (2011) Noninvasive measurements and analysis of blood velocity profiles in human retinal vessels. Invest Ophthalmol Vis Sci 52:4151-7

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