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E. W. Chan, M. C. D. Aquino, P. T. Chew, W. L. Wong, J. L. See; Iris Characteristics in Acute Primary Angle Closure: Comparison Between Attack and Fellow Eyes at Presentation on Anterior Segment Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5543.
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Iris structural characteristics are associated with narrow angles and dynamic iris changes may be related to an increased angle closure risk. This study aims to evaluate the role of the iris in acute primary angle closure (APAC) by comparing iris biometric parameters between APAC and fellow eyes at presentation using anterior segment optical coherence tomography (ASOCT).
Cross-sectional study of 13 consecutive patients presenting with a first unilateral APAC attack to the Singapore National University Hospital Glaucoma Service. ASOCT imaging was performed under dark conditions before medication or laser treatment. Mean measurements of pupil diameter (PD), iris thickness at 500 µm (IT500), iris area at 500 µm (IA500), iris curvature (I-curve) and iris tilt (I-tilt) based on nasal and temporal parameters were quantified with standardized software.
9 females and 4 males were enrolled. The mean time from symptom onset was 12 hours (range 3 to 23). Pupil-block was present in all APAC eyes; fellow eyes did not have plateau iris configurations or thick peripheral iritides. Fellow eyes underwent prophylactic laser iridotomy and none had an APAC event in the next 3 months. The mean PD was larger in APAC than in fellow eyes, although this result was not statistically significant (4.84 µm [95% CI 4.28, 541] vs. 4.32 µm [95% CI 3.60, 5.05], p = 0.23). APAC eyes had significantly lower I-curve than fellow eyes (0.127 µm [95% CI 0.006, 0.248] vs. 0.279 µm [95% CI 0.227, 0.331], p = 0.023). After controlling for PD, the association between I-curve and eye status remained statistically significant (mean difference 0.124 µm [95% CI 0.002, 0.246] respectively, p = 0.047). No significant differences were found in IT500, IA500 and I-tilt between APAC and fellow eyes.
Anterior iris bowing is a feature of APAC independent of pupil size. However, other differences in iris dimensions in APAC eyes compared to the unaffected fellow eyes were not observed, which may be due to the small sample size. Larger studies may be useful to evaluate this association.
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