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.

Determination of iris thickness development in children using swept-source anterior-segment optical coherence tomography

“…Second, our method for the measurement of IT[5,6,7] (i.e., measured from the edge of the pupil) and that used also by Invernizzi A et al,[10] (i.e., measured at the thickest point) were different from those employed in other previous studies[4,8,11] (i.e., measured near the angle). However, the root of the iris exhibits variations.…”

“…In our analysis, the IT was measured from the edge of the pupil in line with the hyperreflective line at the bottom of the iris. The IT was measured twice at 1 and 2 mm (± 0.005 mm) from the edge of the pupil (Fig 1A) used in our previous study,[6,7] and the mean of two measurements was used for subsequent analysis. The eyes of children with large mydriasis in the dark room condition were not suitable for measuring IT because the distal point (2 mm) from the edge of the pupil will locate the angle or cornea.…”

“…Especially, iris thickness (IT) (i.e., CT) is a simple morphological parameter to determine the pathology of the iris. A previous study showed that the IT decreased in patients with Fuch’s uveitis,[4] pseudoexfoliation syndrome,[5] neovascular glaucoma,[6,7] and primary congenital glaucoma. [8] In contrast, it increased in patients with sympathetic ophthalmia.…”

Decreased iris thickness on swept‐source optical coherence tomography in patients with primary open‐angle glaucoma

“…Furthermore, previous studies on glaucomatous eyes have shown that a prolonged increase in the intraocular pressure in POAG eyes might reduce the iris blood volume, resulting in a lower IT. [19][20][21][22] In a histological study, 22 Kubota et al observed that patients with secondary glaucoma with high intraocular pressure had a lower parapapillary choroidal thickness than those with normal intraocular pressure, mainly due to decreased choroidal vessel diameter and choriocapillary vessel collapse. These pathological changes might have also occurred in the iris of the patients with POAG in this study.…”