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Winston Lee, Maarjaliis Paavo, Jana Zernant, Stephen H. Tsang, Janet R Sparrow, Rando Allikmets; Regions of Disease Sparing Spatially Correlate with Choroidal Thinning in ABCA4 Disease. Invest. Ophthalmol. Vis. Sci. 2018;59(9):787. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To study the relationship between choroidal structure and autofluorescence characteristics underlying regions of disease sparing in ABCA4 disease.
Twenty-four patients (n=24) clinically diagnosed with ABCA4 disease were prospectively studied. Disease-causing mutations were found in all patients by direct sequencing of the ABCA4 gene. Main outcome measures choroidal thickness on swept source-optical coherence tomography (SS-OCT) scans, spectral domain-optical coherence tomography (SD-OCT), quantitative autofluorescence (qAF, 488-nm), near infrared-autofluorescence (NIR-AF, 787-nm) and ultra-wide field autofluorescence (532-nm).
Funduscopic examinations revealed early to advanced stage ABCA4 disease-associated characteristics in all patients. Circumsparing of the parapapillary (PP) region was visible on standard retinal imaging (SW-AF, NIR-AF and SD-OCT) in all patients, including 14 patients in whom disease changes (flecks and atrophy) progressed to this portion of the retina and the remaining 10 patients who presented with either a bull’s eye maculopathy lesion or atrophy that was confined to the central macula. The inferonasal (IN) region of the macula (below the optic nerve) was also noted to have fewer disease-related changes relative to other adjacent regions of the optic nerve and macula. The PP/IN regions consistently exhibited the lowest qAF intensities across the macula in 95% of analyzed eyes. Choroidal thickness varied across the posterior pole (9mm x 12mm) but was thinnest in the PP/IN regions in 96% of studied eyes. An ETDRS grid centered over the optic nerve revealed a significant difference in mean choroidal thickness of both eyes (p<0.05) between the outer inferior subfield (145.1 µm) and the outer superior subfield (197.3 µm). A comparative analysis across imaging modalities revealed spatial agreement between regions of visible sparing of disease changes with regions of lowest qAF and choroidal thickness in the PP/IN retina.
A thin choroid underlying the PP and, to a lesser extent, the IN retina, may reflect a diminished metabolic demand of photoreceptors in this region. Alternatively, this structural deviation may provide less retinoid precursors (derived from the choriocapillaris) to the RPE/photoreceptors and, consequently, result in slower accumulation of lipofuscin (qAF) in this region relative to other parts of the ABCA4 disease-affected retina.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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