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Ravi Keshavamurthy, Joseph Carroll, Jacque L Duncan; The effect of measurement method in determining photoreceptor layer thickness in patients with Best Vitelliform Macular Dystrophy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3846. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Measures of photoreceptor structure in regions unaffected by vitelliform lesions using spectral-domain optical coherence tomography (SD-OCT) in patients with Best Vitelliform Macular Dystrophy (BVMD) have reported conflicting results. Two different quantitative methods were used to compare photoreceptor layer thickness in areas adjacent to vitelliform lesions in BVMD.
This retrospective observational case series assessed 6 eyes of 6 patients from 4 families with BVMD and BEST1 genetic mutations. Thickness of outer retinal layers corresponding to photoreceptor inner and outer segments (IS and OS) was measured using both a segmentation algorithm and longitudinal reflectivity profiles (LRP) from SD-OCT scans in regions of the macula outside vitelliform lesions or regions with subretinal fluid or atrophy. Thickness measures were correlated with data from age-matched controls and with mutations in the BEST1 gene.
The mutations in the subjects with BVMD included Glu292Lys (n=1), Arg218His (n=1), Glu300Lys (n=2), and Val9Ala (n=2). Using segmentation, the mean IS and OS lengths were 26.16 and 43.32 microns, respectively, which were not statistically significantly different from controls (26.46 and 37.31, p=0.6 and 0.4, respectively). In contrast, the LRP method produced mean IS and OS lengths of 34.21 and 34.88 microns, respectively, which were statistically significantly different from controls (p<0.0001). IS and OS lengths measured using the LRP method were generally greater than segmentation measures. Val9Ala mutation was associated with increased OS lengths by both segmentation and LRP methods.
SD-OCT quantification methods and genetic mutations influence the measured photoreceptor IS and OS lengths in areas outside clinically visible vitelliform lesions in patients with BVMD. Care should be taken when comparing photoreceptor thickness values across studies that utilize different measurement methods. In addition, the possibility of genotype-dependent differences highlight the importance of complete and accurate disclosure of the mutation profile of a study population.
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