Iris Morphological Features in Patients with 360° Angle-Closure Neovascular Glaucoma: An Anterior Segment Optical Coherence Tomography Study

Abstract

Purpose: To investigate iris morphological features in 360° angle-closure neovascular glaucoma (NVG) by swept-source anterior segment optical coherence tomography (ASOCT).

Patients and methods: In this retrospective, clinic-based, comparative study, 14 patients with 360° angle-closure NVG and 14 healthy age-matched control subjects were enrolled. All patients enrolled had no prior glaucoma surgery but underwent cataract surgery with intraocular lens implantation. Horizontal scanning images of swept-source ASOCT were analyzed using software calipers in temporal and nasal angle areas. The iris thickness at 1 and 2 mm from the pupil edge, iris length, trabecular meshwork length, peripheral anterior synechia (PAS) length, PAS height ratio (PAS length/trabecular meshwork length), and pupil diameter were measured.

Results: Between the groups, there were no statistically significant differences in iris length, trabecular meshwork length, and pupil diameter (p > 0.05). However, the iris thickness was significantly reduced in the NVG group compared with the control group in the temporal and nasal areas (0.306 vs. 0.563 mm/0.326 vs. 0.645 mm at 1 mm, 0.278 vs. 0.523 mm/0.282 vs. 0.546 mm at 2 mm, respectively) (mean, all p < 0.001). In the NVG group, PAS height ratios were 1.55 ± 0.45 (mean ± standard deviation) (range, 0.58-2.30) and 1.55 ± 0.78 (range, 0.68-3.68) at the temporal and nasal angles, respectively.

Conclusions: In patients with 360° angle-closure NVG, the iris thickness decreased to about 50% of that in healthy subjects, and the PAS length exceeded the trabecular meshwork length by about 1.5 times.

Keywords: Angle closure; Anterior segment optical coherence tomography; Neovascular glaucoma; Peripheral anterior synechia.

Fig. 1

Morphological parameters of the iris and angle measured using swept-source anterior segment optical coherence tomography. a A 43-year-old male patient's left eye suffering from 360° angle-closure neovascular glaucoma as a result of central retinal vein occlusion. PAS, peripheral anterior synechia. b Magnification of the nasal angle of Figure 1a. TM, trabecular meshwork.

Fig. 2

Representative images of the iris and angles in the neovascular glaucoma (NVG) and control groups. Images were obtained from a 35-year-old male with NVG resulting from proliferative diabetic retinopathy and a 34-year-old male as a normal control. A thinner iris and completely closed trabecular meshwork due to a high peripheral anterior synechia were observed in the patient with NVG.