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Beng Beng Ong, mohamed katta, camille yvon, Lu Lin, Nishal Patel; SHRM as a biomarker of disease activity in classic and occult AMD subtypes. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2340.
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The presence of subretinal hyper-reflective material (SHRM) in age-related macular degeneration (AMD is thought to be composed of a combination of vascular network, fibrosis and haemorrhage. However, there has not been much research looking into the dynamic nature of SHRM, as well as its variability within the various subtypes of AMD.
We analysed the behavior of SHRM by conducting a retrospective analysis of Topcon OCT scans of 70 patients with classical or occult choroidal neovascular membranes (CNV) as diagnosed on FFA. Volume measurements were done in two ways: an automated method (whereby the computer software automatically segments and estimates the lesion volume) and a calculated formula method: measurements were made of the maximal length and height of SHRM, and an ellipsoid formula (derived from tumour models) was applied to derive a formula for the SHRM volume. Patients were treated with a PRN regime of anti-VEGF injections.
Occult CNVs tend to have larger SHRM volumes at presentation as compared to classical CNVs (calculated formula: 2.36 mm3 vs 1.16mm3, p<0.01; automated formula: 0.80 mm3 vs 0.58 mm3, p=0.20). After completion of loading of anti-VEGF therapy, both cohorts demonstrated regression of SHRM, with the occult cohort exhibiting a larger proportion of regression than the classic cohort (calculated formula: 58.9% vs 13.5% reduction, automated: 33.9% vs 7.8% reduction). At 12 months, whilst the classical group continued to show modest regression of SHRM (automated: 18% lower at 12 months vs. 7.8% at 4 months), the occult group tended to show a rebound effect and of mean SHRM volume, (automated: 19% lower at 12 months vs. 33.9% at 4 months).The volume calculated by the ellipsoid formula had correlated very strongly with the automated segmented volume (Pearson correlation 0.644, p<.0001), although the calculated formula tended to overestimate the volume of the automated software.
SHRM represents a biomarker of disease activity for AMD. Occult CNVs have larger sizes at presentation, and more refractory to treatment. PRN regime can contribute to regrowth of SHRM as per our results. Also, the use of manual calipers to derive a calculated volume is a viable option where automated segmentation is not available. Plans are underway to also measure SHRM in IPCV and RAP. In the future, we hope to further elucidate the characteristics of SHRM and CNVs with OCT angiography.
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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