Fluorescence Lifetime Imaging Ophthalmoscopy of Mouse Models of Age-related Macular Degeneration

To investigate fluorescence lifetime of mouse models of age-related macular degeneration (AMD) by fluorescence lifetime imaging ophthalmoscopy (FLIO). Two AMD mouse models, apolipoprotein E knockout (ApoE−/−) mice and NF-E2-related factor-2 knockout (Nrf2−/−) mice, and their wild-type mice underwent monthly ophthalmic examinations including FLIO from 3 months of age. After euthanasia at the age of 6 or 11 months, blood plasma was collected to determine total antioxidant capacity and eyes were enucleated for Oil red O (ORO) lipid staining of chorioretinal tissue. In FLIO, the mean fluorescence lifetime (τm) of wild type shortened with age in both spectral channels. In short spectral channel, τm shortening was observed in both AMD models as well, but its rate was more pronounced in ApoE−/− mice and significantly different from the other strains as months of age progressed. In contrast, in long spectral channel, both model strains showed completely opposite trends, with τm becoming shorter in ApoE−/− and longer in Nrf2−/− mice than the others. Oil red O staining at Bruch's membrane was significantly stronger in ApoE−/− mice at 11 months than the other strains. Plasma total antioxidant capacity was highest in ApoE−/− mice at both 6 and 11 months. The two AMD mouse models exhibited largely different fundus fluorescence lifetime, which might be related to the different systemic metabolic state. FLIO might be able to indicate different metabolic states of eyes at risk for AMD. This animal study may provide new insights into the relationship between early AMD-associated metabolic changes and FLIO findings.