We considered the product of optical path length (l) and granule concentration (ng) to be indicative of light absorption by lipofuscin granules. Here, we tested whether this product correlates with calibrated SW- AF measurements published earlier (‘qAF8’ [28, 44, 45]), possibly allowing an estimation of this product (ng · l) in patients with STGD1 based on their qAF8 values. qAF8 values were measured in the posterior pole of the fundus (colored area in the inset). Blue dots represent average values of healthy people of different age-ranges; the red dot represents average values of patients with STGD1 (age < 30 years). Pearson’s correlation (r = 0.97) was significant (P = 0.0259); therefore, a linear regression analysis was performed with data from healthy people (solid line). With the average qAF8 value of patients with STGD1, we extrapolated the value of (ng · l) in STGD1 prior to atrophy of the RPE (red dot).