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Robert Wojciechowski, Pradeep Y Ramulu, Sabyasachi Sengupta, Palaniswamy Krishnamurthy, Srinivasan Kavitha, Periasamy Sundaresan, Rengaraj Venkatesh; Heritability of anterior segment optical coherence tomography parameters in the Indian Family Angle Closure Evaluation. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5818.
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We previously reported a very high sibling recurrence risk of angle-closure (AC) in a South Indian population. In the current study, we report on the heritability (h2) of quantitative parameters measured using anterior segment optical coherence tomography (ASOCT) in 631 individuals in 305 sibships in the Indian Family Angle Closure Evaluation.
AC (i.e., either AC suspects, primary angle closure or primary angle closure glaucoma) and open-angle control (OA) probands and their siblings were examined at the Aravind Eye Hospital glaucoma specialty clinic in Pondicherry, India. All participants received a complete eye examination and full glaucoma workup. ASOCT (Zeiss Visante) was performed on both eyes under ambient light and dark illumination. AC biometric parameters were estimated using automated image analysis software. These included AC width (ACW); AC depth (ACD); AC area; angle-opening distances (AOD); angle recess area (ARA), trabecular-iris spacing (TISA); iris area (IA); iris thickness (IT); maximum iris thickness, iris volume; and iris concavity. Means or first principal components (PC1) of parameters measured at multiple locations and illuminations (e.g., AOD, TISA, etc.) were used as derived traits in the analyses. H2 estimates were obtained for each derived trait using generalized estimating equations and computing the residual within-sibship correlation matrix after adjusting for age and sex.
PC1 explained 47% (IA) to 73% (TISA, AOD) of the variance of AC parameters. H2 of AC parameters ranged from 48% (ACD) to >80% (AOD, ARA, TISA, IT). ACD had a lower (pseudo)h2 in AC sibships (2%; NS) compared to OA sibships (40%). Iridolenticular contact (IC) parameters had relatively low h2 (14-30%) although PC1 for IC explained less than 35% of their variances.
Our results show that AS biometric parameters measured with ASOCT are highly heritable in a South Indian population. Interestingly, ACD—a measure often used as a clinical predictor of AC glaucoma development—was uncorrelated in AC siblings. Though numerous measures were taken at different anatomical locations and illumination conditions, one principal component was generally sufficient to capture >50% of the variability of these parameters, simplifying their clinical interpretation and utility.
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