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Y. Li, D. Huang; Pupil Size and Iris Thickness Difference Between Asians and Caucasians Measured by Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5785.
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© ARVO (1962-2015); The Authors (2016-present)
To measure pupil size and iris thickness with optical coherence tomography (OCT) in Asian and Caucasian eyes.
A time-domain anterior segment OCT prototype system (Optovue, Inc., Fremont, CA) operated at 1.3 µm wavelength was used in the study. The OCT system is capable of a speed of 2000 axial scans per second. Horizontal widefield line scans (16mm wide, 8mm deep in air, 512 axial scans per scan) were used to image the cross-section of the anterior eye. Healthy Asian and Caucasian subjects were prospectively enrolled. Both eyes of the subjects were scanned and the scans were centered at the corneal vertex. The horizontal pupil diameter and iris widths were measured using computer calipers. The average iris thickness was calculated by iris cross-sectional area divided by its width. All scans were performed with room light on. T-test was used to compare the average value between the two ethnic groups. The significant level was set at 0.05.
Nineteen Caucasian (age mean +/- standard deviation 33.8 +/-9.6 yr, 47% female) and 23 Asian (age 32.8+/-7.8 yr, 48% female) subjects were enrolled. The average pupil size was 4.73 +/- 0.85mm for Asian eyes and 4.30 +/- 1.02 mm in Caucasian (p = 0.041). The average iris thickness was 0.55 +/- 0.03 mm and 0.49 +/- 0.05 mm for Asian and Caucasian, respectively (p < 0.00001). The average iris length was 3.50 +/- 0.41 mm in Asian and 3.81 +/- 0.49 mm in Caucasian (p = 0.0019). There was no statistical difference between iris cross-sectional areas (Asian 1.91 +/- 0.22 mm2 vs. Caucasian 1.83 +/- 0.22 mm2, p=0.135).
Asian has larger pupil and thicker iris than Caucasian. This information may be useful in understanding why Asian persons are at a higher risk for primary angle closure glaucoma than Caucasians.
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