September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
A New Definition of Narrow Angles Based on Anterior Segment Optical Coherence Tomography Measurements: The Chinese American Eye Study
Author Affiliations & Notes
  • Natasha Naik
    Ophthalmology, USC Eye Institute, Los Angeles, California, United States
  • Benjamin Xu
    Ophthalmology, USC Eye Institute, Los Angeles, California, United States
  • Paul Israelsen
    Ophthalmology, USC Eye Institute, Los Angeles, California, United States
  • Billy Xiaoyi Pan
    Ophthalmology, USC Eye Institute, Los Angeles, California, United States
  • Dandan Wang
    Ophthalmology, USC Eye Institute, Los Angeles, California, United States
  • Xuejian Jiang
    Ophthalmology, USC Eye Institute, Los Angeles, California, United States
  • Rohit Varma
    Ophthalmology, USC Eye Institute, Los Angeles, California, United States
  • Footnotes
    Commercial Relationships   Natasha Naik, None; Benjamin Xu, None; Paul Israelsen, None; Billy Pan, None; Dandan Wang, None; Xuejian Jiang, None; Rohit Varma, None
  • Footnotes
    Support  Grant EY-017337 from National Eye Institute, Bethesda, MD, and Research to Prevent Blindness, New York, NY.
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 5132. doi:
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      Natasha Naik, Benjamin Xu, Paul Israelsen, Billy Xiaoyi Pan, Dandan Wang, Xuejian Jiang, Rohit Varma; A New Definition of Narrow Angles Based on Anterior Segment Optical Coherence Tomography Measurements: The Chinese American Eye Study. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5132.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Gonioscopy is the current gold standard in the evaluation of narrow angles although it is a poor predictor of which patients will develop elevated intraocular pressure (IOP) and primary angle closure glaucoma. Previous studies comparing gonioscopy and anterior segment optical coherence tomography (AS-OCT) found varying degrees of agreement between the two methods leading researchers to question the clinical role of AS-OCT. Recent work has demonstrated a strong correlation between intraocular pressure and AS-OCT measurements of angle recess area (ARA) in subjects with elevated intraocular pressure. This relationship manifests only for ARA values below a certain threshold which creates a novel OCT-based definition of "narrow.” This study examines the relationship between this threshold value and ARA values from angles that are “narrow” on gonioscopy but do not exhibit elevated IOP.

Methods : We analyzed four OCT images from one eye each of 28 subjects selected from the Chinese American Eye Study (CHES), a population based study of Chinese Americans in Los Angeles, CA. These subjects had IOP less than 21 and gonioscopic grade of 0 or 1 in all four quadrants based on the modified Shaffer grading scale. We calculated ARA values measured 500 micrometers from the sclera spur (ARA500) and compared these values to 0.45 mm2, which has previously been shown to be the mean threshold below which intraocular pressure begins to rise. We also plotted ARA value against gonioscopic grade for each eye to assess their relationship in these “narrow” angle subjects.

Results : Among the 28 subjects with angle grade of 0 or 1 in all four quadrants, the majority had ARA500 values greater than 0.45 mm2 (range 0.047 to 0.124, median = 0.70, STD = 0.021). Only 7 subjects had ARA500 values of 0.45 mm2 or less (range 0.015 to 0.034, median = 0.030, STD = 0.007). The linear regression line of ARA500 values plotted against angle grade revealed a weak correlation between the two (slope = 0.004, R2 = 0.003).

Conclusions : Our results show that in subjects with normal IOP, the majority of angles “narrow” on gonioscopy do not fit the AS-OCT definition of “narrow.” These results coupled with previous results demonstrating a strong correlation between low ARA values and high IOP suggest that AS-OCT might be more effective than gonioscopy in assessing patient risk for elevated IOP.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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