Elsevier

Ophthalmology

Volume 121, Issue 6, June 2014, Pages 1194-1202
Ophthalmology

Original article
Association between Baseline Iris Thickness and Prophylactic Laser Peripheral Iridotomy Outcomes in Primary Angle-Closure Suspects

https://doi.org/10.1016/j.ophtha.2013.12.027Get rights and content

Objective

To evaluate the association between baseline measurements of iris thickness at 3 positions and change in anterior segment biometric parameters after prophylactic laser peripheral iridotomy (LPI).

Design

Prospective clinical cohort study.

Participants

Fifty-two eyes of 52 nonglaucomatous subjects with anatomically narrow angles.

Methods

Anterior segment optical coherence tomography (ASOCT) images captured before and after LPI were analyzed using customized software, the Zhongshan Angle Assessment Program (ZAAP) (Zhongshan Ophthalmic Centre, Guangzhou, China). Differences in preoperative and postoperative measurements for anterior segment biometric parameters were compared by paired Student t tests. Multivariate linear regression models, adjusted for age, sex, ethnicity, and preoperative pupil diameter, were used to examine the association between the baseline measurements of iris thickness at 3 positions and the change in anterior segment biometric parameters after LPI.

Main Outcome Measures

Baseline iris thickness measured at 750 μm from the scleral spur (IT750), iris thickness measured at 2000 μm from the scleral spur (IT2000), and maximal iris thickness (ITM). Changes in iris curvature (ICURV) and trabecular–iris space area at 500 μm from the scleral spur (TISA500) and 750 μm from the scleral spur (TISA750) after LPI.

Results

The ICURV significantly decreased, whereas TISA500 and TISA750 significantly increased after LPI (all P < 0.0001). Lower baseline IT750 was significantly associated with greater postoperative increases in TISA500 and TISA750 (both P < 0.05). Lower baseline IT2000 and ITM were significantly associated with greater postoperative decrease in ICURV (both P < 0.05).

Conclusions

Our results showed that lower baseline measurements of iris thickness are associated with greater decrease in ICURV and increases in TISA500 and TISA750 after LPI. This suggests that eyes with thinner irides undergoing LPI were more likely to exhibit greater magnitude of change in terms of flattening of the iris convexity (i.e., ICURV) and widening of the anterior chamber angle (i.e., TISA500 and TISA750).

Section snippets

Methods

Approval for this prospective study was obtained from the University of California, San Francisco, Committee on Human Research. The study was carried out in accordance with the tenets of the Declaration of Helsinki. Caucasian and Chinese subjects were consecutively recruited from the University of California, San Francisco, general ophthalmology and glaucoma clinics between April 2008 and December 2012. All enrolled subjects provided written informed consent. Inclusion criteria for subject

Results

A total of 74 consecutively enrolled Caucasian and Chinese patients received LPI and agreed to participate in the study during the specified time period. Among them, 22 subjects were excluded from the study for 1 or more of the following reasons: (1) Five subjects could not or did not complete the ASOCT examination; (2) 13 subjects had poor ASOCT imaging quality (evaluated on the basis of corneal reflection, continuity of anterior segment structures, motion artifacts, and indeterminate scleral

Discussion

This study evaluated the association between baseline measurements of iris thickness at 3 positions (IT750, IT2000, and ITM) and the change in anterior segment biometric parameters (ICURV, TISA500, and TISA750) after prophylactic LPI in nonglaucomatous subjects with anatomically narrow angles. Our results showed significant decrease in ICURV and increases in TISA500 and TISA750 after LPI. These findings are consistent with previous imaging studies using ASOCT to examine the morphology of the

References (34)

  • S. Radhakrishnan et al.

    Reproducibility of anterior chamber angle measurements obtained with anterior segment optical coherence tomography

    Invest Ophthalmol Vis Sci

    (2007)
  • R.Y. Lee et al.

    Differences in iris thickness among African Americans, Caucasian Americans, Hispanic Americans, Chinese Americans, and Filipino-Americans

    J Glaucoma

    (2013)
  • J.H. Sun et al.

    Factors associated with anterior chamber narrowing with age: an optical coherence tomography study

    Invest Ophthalmol Vis Sci

    (2012)
  • B.S. Wang et al.

    Increased iris thickness and association with primary angle closure glaucoma

    Br J Ophthalmol

    (2011)
  • American Academy of Ophthalmology Glaucoma Panel

    Preferred Practice Pattern Guidelines. Primary Angle Closure

    (2010)
  • P.J. Foster et al.

    The definition and classification of glaucoma in prevalence surveys

    Br J Ophthalmol

    (2002)
  • R.N. Shaffer

    Primary glaucomas. Gonioscopy, ophthalmoscopy and perimetry

    Trans Am Acad Ophthalmol Otolaryngol

    (1960)
  • Cited by (45)

    • Anterior Segment Imaging for Angle Closure

      2018, American Journal of Ophthalmology
    • Anterior Segment Dimensions Following Laser Iridotomy in Acute Primary Angle Closure and Fellow Eyes

      2018, American Journal of Ophthalmology
      Citation Excerpt :

      In the adjusted model, assigning to the fellow eye did not reach significance, revealing that angle width and iris curvature before LPI can predict LPI efficacy in eyes with APAC and their fellow eyes. Iris thickness, iris curvature, baseline angle opening, and LV are among factors that have been demonstrated to affect the anatomic LPI efficacy.18,22,24,33 In a study by Huang and associates,33 greater preoperative iris curvature and smaller preoperative iris area were predictive of angle widening.

    View all citing articles on Scopus

    Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

    Supported by National Institutes of Health National Eye Institute EY002162 Core Grant for Vision Research, Research to Prevent Blindness, and That Man May See, Inc.

    View full text