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C. Zheng, J. See, P. Chew, K. Bang, S. H. Ong, T. Aung; Dynamic Analysis of Iris Movements in Response to Change in Illumination Using Anterior Segment Optic Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3350.
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© ARVO (1962-2015); The Authors (2016-present)
To analyze dynamic iris and pupil changes in response to change in illumination using anterior segment optic coherence tomography (AS-OCT).
This was a prospective observational study of 21 subjects with primary angle closure (PAC) and 9 with primary open angle glaucoma (POAG) who were recruited from Singapore National Eye Center. Videos of iris-pupil movement in response to dark-light illumination changes were captured with real-time video recording using AS-OCT. Each video was then divided by a video processing software into 600 - 1000 frame images. After dewarping for differing refractive indices at the surfaces of the eye, a computer program (ImageJ, US, National Institutes of Health) was used to adjust for small ocular movements in the different frame images and then analyzed. The following parameters were measured: MVPM (mean velocity of pupil movement), MVITM (mean velocity of iris tip movement), MVAOD500 (mean velocity of change in angle opening distance 500um from the scleral spur); and MVAOD750 (mean velocity of change in angle opening distance 750um from the scleral spur).
The mean age of PAC subjects was 64.24 ± 8.93 and that of POAG subjects was 62.56 ± 9.82 (p=0.547). Approximately 20.000 frame images were analyzed. In response to illumination changes, PAC subjects has slower pupil velocity (MVPM 1.0602 ± 0.2436 mm/sec vs 1.3034 ± 0.3559 mm/sec, p=0.038) and iris tip movement (MVITM 0.5321 ± 0.1937mm/sec vs 0.6905 ± 0.1842mm/sec, p=0.0036). There was no difference between the 2 groups for MVAOD500 ( 0.05488 ± 0.04899mm/sec for PAC group vs 0.05451 ± 0.0506mm/sec for POAG, p=0.978 ); or MVAOD750 ( 0.07076 ± 0.05409mm/sec for PAC group vs 0.06242 ±0.06449mm/sec for POAG, p=0.607).
In response to illumination, PAC eyes had slower iris and pupil movements compared to POAG controls. The rate of change in angle width was similar in the 2 groups.
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