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Xiquan Cui, Scott Fraser; Assess the Function and Health of Retina in vivo with Triple Wavelengths Imaging Multispectral Reflectometry. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2160.
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Photoreceptor (PR) and retinal pigment epithelium (RPE) cells are essential components of retina. Their dysfunction or loss causes various retinal diseases or even blindness. Despite of their importance, until now there is no tool that can provide adequate assessment to their function in an intact eye. We report a functional retina imaging method - triple wavelengths imaging multispectral reflectometry (TW-IMR) - to directly, quickly, quantitatively, and non-invasively assay the health of retina.
Rhodopsin is a critical protein in PR cells. It absorbs light (photobleaching) and converts photons into visual signals. Thus, decreasing density of functional rhodopsin directly leads to the degradation of vision or even blindness. In addition, in order for the photobleached rhodopsin to absorb new photons and capture subsequent light images, it has to be regenerated by the 11-cis-retinal molecules exclusively supplied by the RPE cells in vivo. Therefore, the regeneration speed of rhodopsin allows assessing the health of RPE cells. By probing retina with light of three wavelengths and solving three independent equations, TW-IMR is able to achieve the clean measurement of rhodopsin without the interference of transient metarhodopsin III and eye movement.
We mapped the optical density and regeneration speed of rod rhodopsin in wild-type (Sprague Dawley) and diseased (Royal College of Surgeons) rats with a field-of-view of 30º and resolution of 0.1º. We found that the regeneration of rhodopsin in the diseased rats is >100 fold slower than that of the wild-type rats even when they are both as young as1 month old, which is consistent with the congenital dysfunction of RPE cells in the diseased rats. We were also able to follow the decreasing density of functional rhodopsin in the diseased rats till it becomes undetectable. Our results coincide with the degeneration of PR cells in these rats.
TW-IMR overcomes many challenges of in vivo functional retina imaging and offers a simple, direct, fast, and robust means to assess the health of retina. We anticipate that it will play an important role in the classification, research, diagnosis, treatment, and patient management of retinal diseases (e.g. AMD).
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