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Xincheng Yao, Qiuxiang Zhang, Benquan Wang; Functional Optical Coherence Tomography of Transient Intrinsic Optical Signal Changes in Retinal Rod and Cone Photoreceptors. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5908.
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© ARVO (1962-2015); The Authors (2016-present)
This study is to characterize intrinsic optical signals (IOSs) in retinal photoreceptors, and to test the potential of optical coherence tomography (OCT) mapping of rod and cone functions.
A custom-designed OCT was employed to achieve high spatiotemporal resolution imaging. An adaptive data processing algorithm was developed to achieve a high signal-to-noise ratio (SNR) in single-pass IOS recordings. Grass frog (Rana pipiens), which has rod and cone photoreceptors stratified into different axial depths, was selected for quantitative evaluation of rod and cone responses. Both short (10 ms) and prolonged (500 ms) visible light flashes were employed to evoke fast IOSs in the retina. Variable background light controls were conducted to test IOS difference in rod and cone photoreceptors.
High spatiotemporal resolution OCT revealed robust IOSs, without an averaging requirement for multiple trials. Transient IOSs, which might reflect an early stage of light phototransduction, were consistently observed almost immediately (<4 ms) after retinal stimulation. Combined OCT-IOS (structural-functional) images allowed precise identification of anatomic sources of the IOSs. With visible short (10 ms) flash stimulation, fast IOSs were predominantly observed in the outer retina, particularly in the photoreceptor outer segments (OSs). However, prolonged (500 ms) stimulation evoked additional IOSs in the inner retina, with a delayed time course (1.5-2 s). In the dark condition, transient IOSs were observed in both cone and rod OSs. In contrast, under the light condition, the IOS distribution was significantly shifted to the cone OS area.
In coordination with adaptive data processing, functional OCT enabled robust IOS detection in single-pass measurements. The OS was identified as the primary IOS source in retinal photoreceptors. Comparative study of dark- and light-adapted retinas demonstrated the potential of functional OCT-IOS mapping of rod and cone photoreceptors, which promises a new method for improved detection and treatment evaluation of age-related macular degeneration (AMD) and other eye diseases that can cause photoreceptor damage.
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