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Kaspar Schuerch, Winston Lee, Tobias Duncker, Francois C Delori, Rando Allikmets, Stephen H Tsang, Janet R Sparrow; Longitudinal Analysis of Quantitative Autofluorescence in Recessive Stargardt Disease (STGD1). Invest. Ophthalmol. Vis. Sci. 2017;58(8):4651. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
STGD1 is caused by mutations in the ABCA4 gene. Quantitative autofluorescence (qAF) is increased in patients with STGD1 due to an excessive accumulation of RPE bisretinoid lipofuscin. Whether qAF levels in individual patients continue to increase over time or rather decrease with disease progression due to RPE atrophy and/or photodegradation is unclear. Here, we present longitudinal qAF data over a 4-year period.
107 eyes of 59 STGD1 patients with at least 1 known ABCA4 mutation were included in this analysis. 2 to 6 visits for each patient were included in the analysis. SW-AF images (30°; 486 nm excitation) were acquired using a confocal scanning laser ophthalmoscope modified by the insertion of an internal fluorescent reference. Mean grey levels (GLs) were determined in fundus areas defined by 8 pre-set concentric segments at 7-9° eccentricity. GLs were then normalized to the GL of the internal reference to generate qAF values after accounting for the zero GL, the magnification (refraction), and ocular media absorption. Patients were assigned to 5 fleck groups.
Most patients had qAF levels that were higher than the upper 95% confidence interval of healthy eyes. Over the period of 4 years qAF levels in patients assigned to fleck group 1 (bull’s eye with no flecks), 2 (lesion centric flecks) and 3 (extramacular flecks) remained relatively stable, while qAF levels decreased for patients assigned to fleck group 4 a (confluent flecks) and 4b (resorbed flecks, salt and pepper fundus). In patients carrying the p.G1961E mutation, qAF increased by an average of 3.6% (16.3 qAF units) over the mean follow up period of 2.2(±1.3) years (p=0.08). In other patients exhibiting ABCA4-associated disease, qAF increased or decreased depending on the mutation (non-p.G1961E).
The clinical phenotypes of ABCA4-associated disease range from excessive accumulation of flecks in the posterior pole to central optical gap or central bull’s eye atrophy. Longitudinal studies of STGD1 have tracked the progression of central atrophy, changes in fleck distribution, decreased central vision and deteriorations in the ERG. The qAF approach aids efforts to distinguish between some genotypes (e.g. p.G1961E vs non-p.G1961E), and contributes to an understanding of the natural history of the disease. qAF could serve to assess the efficacy of small molecule and gene therapies in future clinical trials.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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