Effect of Laser Peripheral Iridotomy on Anterior Chamber Angle Anatomy in Primary Angle Closure Spectrum Eyes

Abstract

Purpose: To evaluate the change in trabecular-iris circumference volume (TICV) after laser peripheral iridotomy (LPI) in primary angle closure (PAC) spectrum eyes.

Patients and methods: Forty-two chronic PAC spectrum eyes from 24 patients were enrolled. Eyes with anterior chamber abnormalities affecting angle measurement were excluded. Intraocular pressure, slit lamp examination, and gonioscopy were recorded at each visit. Anterior segment optical coherence tomography (ASOCT) with 3D mode angle analysis scans were taken with the CASIA SS-1000 before and after LPI. Forty-two pre-LPI ASOCT scans and 34 post-LPI ASOCT scans were analyzed using the Anterior Chamber Analysis and Interpretation (ACAI) software. A mixed-effect model analysis was used to compare the trabecular-iris space area (TISA) changes among 4 quadrants, as well as to identify potential factors affecting TICV.

Results: There was a significant increase in all average angle parameters after LPI (TISA500, TISA750, TICV500, and TICV750). The magnitude of change in TISA500 in the superior angle was significantly less than the other angles. The changes in TICV500 and TICV750 were not associated with any demographic or ocular characteristics.

Conclusions: TICV is a useful parameter to quantitatively measure the effectiveness of LPI in the treatment of eyes with PAC spectrum disease.

Figure 1

Trabecular Iris Circumference Volume (TICV). Anterior Segment Optical Coherence Tomography (ASOCT) image exhibiting TISA750 (light green space) and TICV750 (darker green spaces), along with the scleral spur landmark (red circle), iris (yellow), and cornea (violet line) in an open angle.

Figure 2

Comparison images of exhibiting TISA750 in a normal eye (A), before LPI in an eye with PAC spectrum disease (B), and after LPI in the same eye (TISA is indicated by yellow asterisk). TICV is TISA integrated over the peripheral angle.