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Ken Marion, Moritz Niemeyer, Anna Dastiridou, Brian Francis, Srinivas R Sadda, Vikas Chopra; Effects of Ambient Light Level Variation on Spectral Domain OCT-derived Anterior Chamber Angle Metrics in Non-Asians vs. Asians. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1954.
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© ARVO (1962-2015); The Authors (2016-present)
To better understand the effect of ambient light level variation on spectral domain OCT-derived anterior chamber angle metrics in Non-Asians vs. Asians.
Non-Asian (n=24) and Asian participants (n=24) with open angles by gonioscopy had both eyes imaged twice at five strictly controlled, ambient light levels at UCLA Doheny Eye Center. Ethnicity was self-reported.<br /> Light levels strictly controlled using a light meter at 1.0, 0.75, 0.5, 0.25, and 0 foot candle at the eye interface (fce). Each eye was imaged 10 times for a total of 960 assessments in the study. Zeiss Cirrus SD-OCT 5-line raster scans at IC270 irido-corneal angle were measured twice by 2 trained, masked graders from the Doheny Image Reading Center using customized Image J software. Metrics: Schwalbe’s Line-angle-opening-distance (SL-AOD) and SL-trabecular-iris-space area (SL-TISA). Delta change differences in measurements from brightest to darkest ambient light levels were computed. Statistical analysis completed using MedCalc v18.104.22.168.
Non-Asian eye angle metrics (SL-AOD 0.443±0.114mm/SL-TISA 0.330±0.105mm2) are significantly larger (~38%, p=0.016) than Asian eyes (SL-AOD 0.322±0.120mm/SL-TISA 0.237±0.092mm2)(Graph 1, Table 1a). Asian eyes are more susceptible to light variations compared to Non-Asian eyes (repeated measures ANOVA, p=0.009). Light meter reading 1.0 to 0 fce; Non-Asian Δ change SL-AOD 7.89%, SL-TISA 10.71% vs. Asian eyes Δ change SL-AOD 13.39%, SL-TISA 16.54% (Table 1b). Excellent Intra- and Inter-grader reproducibility/reliability (Table 1c).
Anterior chamber angle morphometrics are exquisitely sensitive to changes in ambient illumination in all populations, especially in Asian eyes. Schwalbe’s-line based ACA metrics from the Cirrus SD-OCT could be measured with excellent intra- and inter-grader reproducibility. These findings highlight the need to strictly control lighting conditions in order to obtain reproducible measurements of anterior chamber geometry.
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