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Ophthalmology. 2010 Jan;117(1):3-10. doi: 10.1016/j.ophtha.2009.10.030. Epub 2009 Nov 17.

Optical coherence tomography quantitative analysis of iris volume changes after pharmacologic mydriasis.

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Department of Ophthalmology, Edouard Herriot Hospital, Lyon 1 University, Lyon, France.



To describe a method using anterior segment optical coherence tomography (AS OCT) for estimating iris volume. To quantify changes in iris volume induced by pharmacologic mydriasis in narrow-angle eyes predisposed to angle-closure compared with normal open-angle eyes.


Cross-sectional study.


Thirty fellow eyes of 30 patients who had an episode of primary acute angle-closure and 30 eyes of 30 normal age- and gender-matched subjects with open angles. All fellow eyes had a patent laser peripheral iridotomy.


Iris volume and all biometric measurements were performed before and after instillation of 1% tropicamide and at least 1 week later 10% phenylephrine. Iris volume was estimated using AS OCT radial sections of the iris and a customized image-processing software.


Iris volume, pupil diameter, angle configuration including angle opening distance at 500 mum (AOD 500) and trabecular-iris space at 500 mum (TISA 500), AS OCT anterior chamber depth, and A-scan ultrasonography axial length before and after pupil dilation.


Iris volumes measured before dilation of the pupil were 44.94+/-2.1 mm(3) and 44.29+/-3.9 mm(3) in the fellow eyes and open-angle eyes, respectively, which was not significantly different (P>0.1). Thirty minutes after instillation of 1% tropicamide, mean iris volume increased significantly in the fellow eyes (from 44.94+/-2.1 mm(3) to 49.92+/-2.9 mm(3); P<0.01), whereas it decreased significantly in the open-angle eyes (from 44.29+/-3.9 mm(3) to 37.88+/-2.2 mm(3); P<0.01). Similar changes were observed after instillation of 10% phenylephrine. Based on multivariate analysis, significant predictors of increase in iris volume after pupil dilation were eyes predisposed to angle-closure compared with open-angle eyes (P = 0.008), larger pupil diameter (P = 0.02), and brown eyes (P = 0.01). Relative iris volume increase was correlated significantly with AOD 500 and TISA 500 relative decrease in the narrow-angle group (P<0.05).


The iris volume may be estimated with AS OCT. The iris volume increases after pupil dilation in narrow-angle eyes predisposed to acute angle closure. In those patients, this biometric change is associated with a narrowing of the angle despite a patent laser peripheral iridotomy.


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

[Indexed for MEDLINE]

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