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Syril Dorairaj, Anup Pant, Jason Calhoun, Rouzbeh Amini; Quantitative Analysis of Anterior Segment Biometric Parameters in Controlled Light Conditions after Laser Peripheral Iridotomy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4999. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the anterior segment biometric parameters during dilation induced by controlled light intensity.
A light controlling device capable of emitting light at four different intensities (0-300 lux) was designed and built for this study. Six eyes from four patients, who previously underwent laser peripheral iridotomy, were imaged using ultrasound biomicroscopy (UBM) imaging. The eyes were subjected to four levels of light intensity starting at 300 lux and decreasing in 100 lux increments to dark condition (~0 lux). The UBM images were further analyzed using internally developed image analysis software. Different anterior segment parameters such as angle opening distance (AOD) 500, iris cross sectional area, iris volume, and pupil diameter were quantified. Data from one of the patients who received dilation medication prior to the test was excluded from the analysis (n=5 used in all analyses).
As shown in Fig. 1, all measured parameters changed as the light intensity altered. In particular, AOD 500 decreased from 0.61 ± 0.10 mm (mean ± standard error) at the light intensity of 300 lux to 0.50 ± 0.01 mm, at the dark condition. Both the iris cross sectional area and the iris volume decreased when the light intensity was reduced. The iris volume was particularly larger at the highest intensity level of 300 lux (69.90 ± 4.35 mm3) compared to the other light levels (63.95 ± 6.89 mm3, 64.19 ± 4.03 mm3, and 63.50 ± 5.08 mm3 for 200, 100, and 0 lux, respectively). Pupil diameter was found to be increasing as the light intensity decreased with a maximum standard error of 0.40 mm.
In this study, for the first time, we developed a device to measure anterior segment biometric parameters for a range of light intensities. We observed that during the transition from dark to light conditions, the anterior segment biometric parameters altered continuously.
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