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S. Osmanovic, S. Radhakrishnan, S. Lin, M. Pekmezci, M. He; Variable Change in Angle Morphology After Iridotomy Between Whites and Chinese. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5524.
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Prior literature has explored the notion that angle closure has distinct etiologies and a different natural history in East Asian populations when compared to Western Caucasian populations, and thus it may respond differently in these groups following Laser Peripheral Iridotomy (LPI). Anterior Segment Optical Coherence Tomography (AS-OCT) is a novel imaging modality that has proven useful for the assessment of primary angle closure (PAC) and for visualization of anatomic changes following LPI. We report on differential effects on angle morphology following LPI in Chinese and White patients at a single university-based clinic.
In this retrospective study, we examined AS-OCT images before and after LPI in cohorts of consecutive Chinese and Caucasian patients diagnosed with PAC, PAC glaucoma, or PAC suspicion. Main outcome measurements were the mean differences in established angle parameters (Angle Opening Distance, Trabecular Iris Segmental Area, Angle Recess Area) in temporal and nasal angles as calculated by custom software. Mixed effects regression analyses were performed to account for the use of both eyes in some patients. We also examined the percentage of patients in each group that remained narrow by gonioscopy and AS-OCT cutoff criteria.
From Jan 2008 to Sept 2009 there were 31 Chinese eyes and 36 Caucasian eyes treated with LPI and all angle parameters were increased in both groups following LPI. The mean difference post LPI was significantly greater in Caucasian patients for all 6 measurement variables in both temporal and nasal angles. P-values ranged from .0001 to .043. Additionally, 61% of Chinese and 25% Caucasian remained narrow by AS-OCT criteria (p= .0027), and 58% and 33% respectively per gonioscopy grading (p=.034).
By all angle measures (AOD, TISA, ARA), Caucasians demonstrated greater angle opening than Chinese for both temporal and nasal angles of the eye, along with less persistence of narrow angles after iridotomy. Our data indicate that there is a potential for greater anatomic angle opening in Caucasians versus Chinese as measured by AS-OCT imaging. This suggests that other mechanisms such as plateau iris are more common in Chinese than Caucasians and that the utility of LPI may be different between these groups.
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