Morphologic features of iris in highly myopic eyes based on a novel swept-source optical coherence tomography

Background

To investigate the morphologic features of iris in the highly myopic (HM) eyes using a novel swept-source optical coherence tomography (SS-OCT).

Methods

In this retrospective case-control study, 100 eyes of 100 patients scheduled to have cataract surgery were included, categorized into the control (22 mm< AL < 24.5 mm) and HM (AL ≥ 26 mm) groups. Iris volume (IV), area of anterior iris surface (IS), area of posterior IS, and average iris thickness (IT), as well as anterior chamber volume (ACV) and trabecular-iris space at 500 µm (TISA 500) were evaluated using SS-OCT. The associated factors with morphologic features of iris were also investigated.

Results

The HM group showed significantly larger IV and area of anterior and posterior IS than the control group (all P < 0.001), while no difference was identified in IT between the groups. Similar trend in IV was seen in the superior and nasal segments, and area of anterior and posterior IS showed similar trends in all segments except the temporal segment. The IV, area of anterior and posterior IS were all positively correlated with AL (all P < 0.001). Multivariate linear regression revealed that a larger IV was associated with greater ACV. Both larger areas of anterior IS and posterior IS were associated with male, longer AL, greater ACV, and smaller TISA 500.

Conclusions

The HM eyes showed larger IV and area of IS than the control eyes, indicating a coronal expansion of the iris with AL. Iris morphology correlated with anterior chamber angle configuration.