Personalized lens correction for quantitative fundus autofluorescence measurements

Abstract

Purpose : Quantitative fundus autofluorescence (QAF) currently uses an age-based average score to correct for lens opacification. In aged populations, however, lens opacification may vary to large degree between individuals and innate lens autofluorescence (AF) is not incorporated into the correction formula. Consequently, phakic subjects >60 years are often excluded from QAF studies in retinal diseases. Our goal was to develop and compare an individualized correction formula based on measurements of lens opacification and AF.

Methods : A total of 27 eyes of 27 subjects (12 female, age 70 ± 27 (mean ±SD)) underwent multimodal imaging including Scheimpflug, anterior chamber optical coherence tomography (AC-OCT), lens quantitative autofluorescence (LQA) and retina QAF imaging prior to cataract surgery and two weeks post-operatively. QAF values were measured at the middle “Delori ring”, QAF8. LQA, normalized mean reflectivity of the lens compared to the cornea of AC-OCT, and the pentacam nucleus score (PNS) was computed at baseline. Least absolute shrinkage and selection operator (LASSO) and random forest regression was performed to predict the difference between QAF measurements and to assess the putative importance of determinants pre- and post cataract extraction.

Results : The PNS and LQA measurements were selected by the LASSO regression as the most relevant variables (cross-validated R2=0.59), whereas AC-OCT measurements and age were eliminated by backward selection. Both PNS and LQA were associated with a decrease in QAF values. The mean absolute error for QAF difference was statistically significant improved with 49.5 ± 37.5 QAF a.u. (mean ± SD) compared to the current age-based estimate 98.3 ± 94.6 QAF a.u. (p< 0.01).

Conclusions : LQA measurements revealed that lens AF estimates lens opacification rather than contributing to the AF signal of the fundus. A personalized correction factor based on lens opacification and AF measurements could increase the accuracy of retina QAF imaging – and might enable to include aged phakic patients in future QAF studies.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.