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Ce Zheng, Carol Y. Cheung, Paul Tec Kuan Chew, Tin Aung, Sim Heng Ong; Analysis Of Vector Acceleration Of Iris Constriction In Response To Dark Light Illumination Using Anterior Segment Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6277.
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© ARVO (1962-2015); The Authors (2016-present)
To describe a method using anterior segment optical coherence tomography (AS_OCT) for quantitatively estimating vector acceleration of iris constriction in response to dark and light change and evaluating their association with anterior chamber angle area.
This was a prospective observational study. Study subjects were recruited from Singapore Eye Research Institute. Videos anterior chamber changes in response to dark-light illumination were captured with real-time video recording from AS_OCT. The relationship between the pupil diameter and time was modeled by 2nd order polynomial function. The vector acceleration will further divided into vector acceleration between iris and lens (Acc_PB and Angle_PB) and vector acceleration to constrict the pupil (Acc_PC and angle PC). The pupil diameter (PD), anterior chamber angle area (trabecular iris space area (TISA500)), iris thickness were also measured by customized software as well. The average of temporal and nasal measured values was used for analysis. The associations between vector acceleration and corresponding angle with other biometric parameters were evaluated with univariate and multivaria te regression analyses.
A total of 138 of 166 eligible videos were available for analysis. Using gonioscopic grading as the reference, 50 subjects with open angles and 88 subjects with closed angles were evaluated. The Acc_PC was larger in eyes with open-angle than the eyes with closed-angle, after adjusting for age and anterior chamber width (0.864 mm/sec2 vs. 0.562 mm/sec2, p = 0.007), whereas Acc_PB was smaller in eyes with open-angle than the closed-angle eyes (0.040 mm/sec2 vs. 0.118 mm/sec2, p < 0.000). The Angle_PC was larger in the eyes with close-angle than open-angle (12.012 vs 2.563, p < 0.000). No significant difference was found for Angle_PC bewteen two groups (p = 0.649). Based on multivariate analysis, Acc_PB and Angle_PC was both significantly associated with the presence of narrow angle after adjust for age, cup-to-disc ratio, axil length and anterior chamber width.
The vector acceleration of pupil constriction in response to dark-light illumination may be estimated with AS OCT. Angle_closure eyes tend to have bigger Acc_PB and larger Angle_PC than those of health control eye.
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