Iris Crypts Influence Dynamic Changes of Iris Volume

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• 作者：Jacqueline Chua ; PhD¹ ; ² ; Sri Gowtham Thakku ; BEng¹ ; Tin A. Tun ; MD¹ ; Monisha E. Nongpiur ; MD ; PhD¹ ; ² ; Marcus Chiang Lee Tan ; MBBS¹ ; Michael J.A. Girard ; PhD¹ ; ³ ; Tien Yin Wong ; FRCS ; PhD¹ ; ² ; ⁴ ; Joanne Hui Min Quah ; MMed⁵ ; Tin Aung ; FRCS ; PhD¹ ; ² ; ⁴ ; Ching-Yu Cheng ; MD ; PhD¹ ; ² ; ⁴ ; ^{chingyu.cheng@duke-nus.edu.sg" class="auth_mail" title="E-mail the corresponding author}
• 关键词：AOD ; angle opening distance ; AS-OCT ; anterior-segment optical coherence tomography ; CI ; confidence interval ; CIE ; Commission Internationale de l'Eclairage ; PAC ; primary angle closure ; PACG ; primary angle-closure glaucoma ; SS-OCT ; swept-source optical coherence tomography ; 3D ; 3-dimensional
• 刊名：Ophthalmology
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：123
• 期：10
• 页码：2077-2084
• 全文大小：511 K

文摘

To determine the association of iris surface features with iris volume change after physiologic pupil dilation in adults.

Design

Cross-sectional observational study.

Participants

Chinese adults aged ≥ 50 years without ocular diseases.

Methods

Digital iris photographs were taken from eyes of each participant and graded for crypts (by number and size) and furrows (by number and circumferential extent) following a standardized grading scheme. Iris color was measured objectively, using the Commission Internationale de l’Eclairage (CIE) L* color parameter (higher value denoting lighter iris). The anterior segment was imaged by swept-source optical coherence tomography (SS-OCT) (Casia; Tomey, Nagoya, Japan) under bright light and dark room conditions. Iris volumes in light and dark conditions were measured with custom semiautomated software, and the change in iris volume was quantified. Associations of the change in iris volume after pupil dilation with underlying iris surface features in right eyes were assessed using linear regression analysis.

Main Outcome Measures

Iris volume change after physiologic pupil dilation from light to dark condition.

Results

A total of 65 Chinese participants (mean age, 59.8±5.7 years) had gradable data for iris surface features. In light condition, higher iris crypt grade was associated independently with smaller iris volume (β [change in iris volume in millimeters per crypt grade increment] = −1.43, 95% confidence interval [CI], −2.26 to −0.59; P = 0.001) and greater reduction of iris volume on pupil dilation (β [change in iris volume in millimeters per crypt grade increment] = 0.23, 95% CI, 0.06–0.40; P = 0.010), adjusting for age, gender, presence of corneal arcus, and change in pupil size. Iris furrows and iris color were not associated with iris volume in light condition or change in iris volume (all P > 0.05).

Conclusions

Although few Chinese persons have multiple crypts on their irides, irides with more crypts were significantly thinner and lost more volume on pupil dilation. In view that the latter feature is known to be protective for acute angle-closure attack, it is likely that the macroscopic and microscopic composition of the iris is a contributing feature to angle-closure disease.