Quantitative Fundus Autofluorescence: Advanced Analysis Tools

Abstract

To use multimodal retinal images (including quantitative fundus autofluorescence [QAF]) for spectral-domain optical coherence tomography (SD-OCT)-based image registration and alignment. For each age decade of healthy adults, normative fine-grained QAF retinal maps are generated and advanced methods for QAF image analysis are applied. Methods: Multimodal retinal images were obtained from 103 healthy subjects (age 19-77 years; unremarkable retina/macula, age-appropriate clear optic media). Custom written FIJI plugins enabled: (1) determination of the fovea in SD-OCT and the edge of the optic disc in infrared (IR) images; (2) alignment and superimposition of multimodal retinal images based on foveal and optic disc position; (3) plotting of normative QAF retinal maps for each decade; and (4) comparison of individual retinas with normative retinas of different decades using newly introduced analysis patterns (QAF97, freehand tool). Results: SD-OCT based image registration enables easy image registration, alignment, and analysis of different modalities (QAF, IR, and SD-OCT here reported). In QAF, intensities significantly increase with age with two major inclines between the third/fourth and seventh/eighth decades. With aging, the parafoveal area of maximum QAF intensity slightly shifts from temporal-superior to temporal. Compared with standard QAF analysis, refined QAF analysis patterns reveal a more detailed analysis of QAF, especially in the diseased retina. Conclusions: Age-related QAF normative retinal maps can be used to directly compare and classify individual's QAF intensities. Advanced QAF analysis tools will further help to interpret autofluorescence changes in normal aging and in the diseased retina in a multimodal imaging setting. Translational Relevance: Advanced methods for QAF analysis link basic findings with clinical observations in normal aging and in the diseased macula.

Quantitative Fundus Autofluorescence in Systemic Chloroquine/Hydroxychloroquine Therapy

“…Furthermore, well-trained technical assistance is required to guarantee reliability and repeatability of QAF imaging. Previous studies in our cohorts showed mean variability of about 8% in normal subjects 37 and <12% in patients with maculopathy, comparable to results from other groups. 31 In conclusion, this study is a prospective preclinical report on increased quantitative short wavelength FAF during CQ/HCQ treatment, compared to QAF of healthy controls.…”

“…Furthermore, well-trained technical assistance is required to guarantee reliability and repeatability of QAF imaging. Previous studies in our cohorts showed mean variability of about 8% in normal subjects 37 and <12% in patients with maculopathy, comparable to results from other groups. 31 …”

“…As shown in our study, especially in the maculopathy patients, QAF8 analysis does not capture the affected areas and more flexible analysis patterns (narrowing of the analysis field, flexible dimensions, free hand tools) are warranted to specifically analyze the respective areas. 37,71 Limitations of this study include an imbalance according to gender, which is due to prevalence and incidence of the rheumatologic disorders and CQ/HCQ drug indications. Furthermore, cumulative dose and intake duration are mostly based on patient recall and were only partially available from documented patient charts, which might have led to unprecise cumulative doses in patients with longlasting intake.…”

“…As shown in our study, especially in the maculopathy patients, QAF8 analysis does not capture the affected areas and more flexible analysis patterns (narrowing of the analysis field, flexible dimensions, free hand tools) are warranted to specifically analyze the respective areas. 37 , 71 …”

“…S2). Bisecting each ring segment of the original QAF grid and extending it toward the fovea results in a total of 97 segments (including the foveal area), 37 plus a parafoveal ring ( Supplementary Fig. S2).…”