Abstract
We introduced a new method for detecting iris surface furrows and identify its associations with dynamic changes in iris volume in healthy eyes. Swept-source optical coherence tomography was performed on 65 subjects with open angle under light and dark conditions. Iris boundaries were identified and a reconstruction of the anterior iris surface was obtained. Furrows were detected by identifying locally deep (minima) points on the iris surface and reported as furrow length in millimetres. Iris volume was quantified. Associations between furrow length and dynamic changes in iris volume were assessed using linear regression model. With pupil dilation, furrow length increased (15.84 mm) whereas iris volume decreased (−1.19 ± 0.66 mm3). Longer furrow length was associated with larger static iris volume, as well as smaller loss of iris volume with pupil dilation (β = −0.10, representing 0.1 mm3 less loss in iris volume per 10 mm increase in iris furrow length; P = 0.002, adjusted for age, gender and changes in pupil size). Our iris furrow length measurements are robust and intuitive. Eyes with longer furrows have larger iris volume and lose less volume during physiological pupil dilation. These findings highlight the potential for iris surface features as indicators of iris morphological behavior.
Highlights
There are several features that can be found in the surface of the human iris, including crypts and contraction furrows
We developed an automated tool to measure iris furrow length using images acquired from anterior segment swept-source optical coherence tomography (SS-OCT)
We applied this new technique on a set of study eyes and were able to identify an association between iris furrow length and changes in iris volume during physiological pupil dilation
Summary
There are several features that can be found in the surface of the human iris, including crypts and contraction furrows. A possible reason for this is that the assessment of iris furrows was based on a three-point grading scale[16] While this grading system has allowed us to identify significant associations with static iris thickness[16] and volume[17], having only 3 grades may be less sensitive in capturing the full range of variations in iris characteristics among study subjects. Our novel method was able to provide an objective and more quantitative measurement of the actual length of iris furrows, and is more sensitive to capture the full variations in furrow length We applied this new technique on a set of study eyes and were able to identify an association between iris furrow length and changes in iris volume during physiological pupil dilation
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