Purpose
Age-related macular degeneration (AMD) is the leading cause of blindness in industrialized countries. AMD is characterized by changes in the supportive cells of the retina, the retinal pigmented epithelium (RPE). Over time, the RPE accumulates fluorescent organelles, called lipofuscin, that contain engulfed photoreceptor fragments. An attractive hypothesis is that RPE lipofuscin accumulation helps drive the detrimental changes in AMD. Quantitative auto-fluorescence (qAF) is a surrogate for measurement of RPE lipofuscin. RPE qAF increases over time (Ach et al., 2014), however the trend in older populations is unknown. Such studies are challenging due to age-related changes in the lens and vitreous that may affect light transmission. We aim to determine the trend of qAF in healthy patients over age 50 with pseudophakia.
Methods
Healthy pseudophakic patients over age 50 were recruited. Approval was obtained from the NYU School of Medicine IRB. Prior to imaging, consent and background medical information were obtained. Following pupil dilation, spectral-domain optical coherence tomography (SD-OCT) images of the macula were captured with a Spectralis HRA+OCT (Heidelberg) to detect retinal pathology for study exclusion. qAF images were obtained by Spectralis with an internal fluorescence reference (Delori et al., 2011). Resultant images were uploaded into Igor Pro software (WaveMetrics) to generate qAF intensity maps calibrated to the internal reference and corrected for intraocular lens type (blue-blocker or clear).
Results
27 patients (31 eyes) were enrolled. Demographic information will be presented. Mean qAF was calculated in an annular region surrounding the fovea for each patient (Greenberg et al., 2013). Between the ages of 50 and 75 years (18 patients, 21 eyes) qAF increased. Interestingly, between the ages of 75 and 90 years (9 patients, 10 eyes) qAF declined (figure, linear fits).
Conclusions
We show that qAF indeed displays a linear overall increase until age 75-80 years, as previously suggested (Ach et al., 2014), but then appears to decline thereafter. Because RPE cell number and health appears to be maintained to old age (Ach et al., 2014), we hypothesize that decreasing qAF after age 75 may be due to changes in lipofuscin turnover. Further recruitment of normal and AMD subjects is indicated to study the role of lipofuscin in health and disease.