Characterizing And Identifying The Fluorescence Lifetime Of The In Vivo Human Rpe Cellular Mosaic PDF Download

"The retinal pigment epithelium (RPE) is a cell layer in the back of the eye essential for ocular health. With age, the RPE naturally accumulates autofluorescent material called lipofuscin, just one of many retinal fluorophores. Fluorescence is useful for diagnosing and tracking retinal disease. Beyond measuring intensity fluorescence lifetime imaging ophthalmoscopy (FLIO) varied with fluorophore composition and environmental factors that may provide critical insight into retinal mechanisms. Adaptive optics ophthalmoscopy can target specific retinal layers or individual cells. This thesis characterizes the in vivo human RPE layer using AOFLIO and investigates potential sources of change across the retina and with age. Firstly, it demonstrates the safety and repeatability of AOFLIO in human subjects with green-light excitation at 532 nm. By imaging at both the 532 nm spectral channel and mimicking the clinical device with two blue-light excitation channels - the long spectral channel (LSC) and short spectral channel (SSC) - I found that there was a high correlation between the LSC and 532 nm channel with a near-constant offset between the two lifetimes. That is likely because of a higher relative contribution of melanin to the 532 nm channel. To elucidate how AOFLIO results can be translated into the clinic, some subjects were also imaged with clinical FLIO. The AO LSC was well correlated with the clinical LSC, making the comparison simple between those channels. The AO 532 nm channel and the clinical LSC were not well correlated. The in vivo human signal in all 3 channels was compared to that from endogenous fluorophores in cuvettes. These results indicated that the main sources of fluorescence in the 532 nm channel are lipofuscin, melanin, and FAD where the increase of fluorescence lifetime with age can be attributed to the increase of melanolipofuscin which likely pulls the lifetime signal longer. Lastly, the cell-to-cell dynamics were investigated which found lifetime increases with age and eccentricity. The AO SSC changes were found to also be likely due to melanin changes across the retina. Future work will include applying AOFLIO to disease eyes to begin probing the dynamics of change with retinal degeneration."--Pages xiii-xiv.