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Won Kyung Song, Anika Nanda, Jasmina Cehajic-Kapetanovic, Robert E MacLaren; Enhanced autofluorescence ring findings in RPGR-associated retinitis pigmentosa. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4524.
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© ARVO (1962-2015); The Authors (2016-present)
X-linked retinitis pigmentosa (RP) caused by mutations in the RPGR gene is a common cause of inherited blindness in young people. There is particular interest in the RPGR phenotype due to the recently commenced gene therapy clinical trials. An enhanced ring on autofluorescence (AF) imaging is sometimes seen in RP patients and correlates with vision loss. However, the relationship between outer retinal degeneration and the enhanced ring has not so far been investigated.
This was a retrospective non-interventional study. Among 38 consecutive patients, 19 eyes of 10 patients with enhanced AF rings were included. Excluded eyes were due to: (1) no ellipsoid zone (EZ) remaining, (2) poor image quality, and (3) enhanced AF ring extending beyond the image. Measurements in the transfoveal horizontal plane were performed by two independent observers.
The mean inner width of the enhanced ring was 2.4±1.2 mm in the right eyes and 2.6±1.4 mm in the left. The mean outer width was 3.9±1.4 mm in the right eyes and 4.0±1.6 mm in the left. The mean EZ horizontal width at the same plane of the OCT in the right eyes was 2.8±1.2 mm and 2.9±1.3 mm in the left. The mean external limiting membrane (ELM) width was 4.0±1.4 mm in the right and 4.1±1.6 mm in the left. Statistical analysis between AF and OCT measurements showed a correlation between the ring inner width and the edge of the EZ (right eyes: first observer r=0.951; second observer r=0.907; left eyes: first observer r=0.961; second observer r=0.957, p<0.001 in all analysis). Conversely, the outer ring width was correlated to the width of the ELM (right eyes: first observer r=0.852; second observer r=0.898; left eyes: first observer r=0.965; second observer r=0.963, p<0.001 in all analysis). Measurements performed by two individual observers all showed high repeatability (p<0.001 for all measurements).
About a quarter of RPGR patients have a clear hyperfluorescent ring visible in the central macula on autofluorescence. This ring appears to correlate with the region of retina that has lost the EZ but still has an intact ELM. Anatomically this would correspond to degenerating photoreceptors that have lost the outer segment, but not yet the inner segment.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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