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

Area of Science:

• Ophthalmology
• Medical Imaging
• Anatomy

Background:

• Iris volume changes are critical in angle-closure glaucoma.
• Pharmacologic mydriasis is commonly used in ophthalmologic examinations.
• Understanding iris dynamics is essential for managing narrow-angle eyes.

Purpose of the Study:

• To introduce a method for iris volume estimation using anterior segment optical coherence tomography (AS OCT).
• To quantify iris volume changes induced by pharmacologic mydriasis.
• To compare these changes in narrow-angle eyes versus normal open-angle eyes.

Main Methods:

• A cross-sectional study involving 30 narrow-angle eyes and 30 normal open-angle eyes.
• Iris volume was measured using AS OCT before and after pupil dilation with tropicamide and phenylephrine.
• Key outcome measures included iris volume, pupil diameter, and angle configuration (AOD 500, TISA 500).

Main Results:

• Iris volume increased significantly in narrow-angle eyes after mydriasis (P<0.01) but decreased in open-angle eyes (P<0.01).
• Predictors of iris volume increase included predisposition to angle-closure, larger pupil diameter, and brown irides.
• Increased iris volume correlated with angle narrowing (decreased AOD 500 and TISA 500) in narrow-angle eyes.

Conclusions:

• AS OCT provides a reliable method for estimating iris volume.
• Pupil dilation causes iris volume to increase in eyes predisposed to angle-closure.
• This iris biometric change contributes to angle narrowing, even with a patent iridotomy.