In Vivo Assessment of the Pediatric Trabecular Meshwork, Schlemm Canal, and Iridocorneal Angle Using Overhead-Mounted Optical Coherence Tomography

Abstract

Purpose: To describe the in vivo morphologic characteristics of the trabecular meshwork (TM), Schlemm canal (SC), and iridocorneal angle in pediatric patients with normal eyes, glaucoma, and cataract.

Design: Prospective cohort study.

Study population: A total of 41 children (70 eyes) were enrolled, comprising 28 normal eyes, 19 eyes with glaucoma, and 26 eyes with cataract (15 pre-, 11 post-lensectomy). Average age was 2.8 ± 3.0 years at imaging.

Methods: Pediatric patients undergoing clinically indicated examination under anesthesia underwent overhead-mounted optical coherence tomography (OCT) imaging of the outflow pathway. Images were then evaluated for abnormalities in the outflow pathway.

Main outcome measure: Presence of thickened TM, SC patency, any iridocorneal angle malformation, and episcleral vessel patency in normal eyes vs all other eyes.

Results: Thickened TM tissue was found in no normal eyes, 47.4% of eyes with glaucoma, and 53.8% of eyes with cataracts. A patent SC was demonstrated in all normal eyes, 32% with glaucoma, and 65.4% with cataracts. Iridocorneal angle abnormality was identified in no normal eyes, 94.7% with glaucoma, and 69.2% with cataracts. Prevalence of iridocorneal angle abnormality was similar in cataract eyes pre- and post-lensectomy. All but one eye with glaucoma secondary to anterior segment dysgenesis had patent episcleral vessels. Intraocular pressure (IOP) at imaging was lower in eyes with than without a patent SC (13.9±3.8 mm Hg vs 28.2±11.7 mm Hg, P < .001). IOP was lower in eyes with normal iridocorneal angles compared to those with angle malformation (13.9±3.2 mm Hg vs 22.6±12.1 mm Hg, P < .001). There was no significant difference in IOP between eyes with normal TM thickness compared to those with thickened TM (17.4±8.2 mm Hg vs 17.4±9.5 mm Hg, p = 0.943).

Conclusion: Eyes of children with glaucoma demonstrated thickened TM, decreased patency of SC, and abnormalities of the iridocorneal angle on OCT imaging, compared with normal controls. These abnormal findings also appear in many pediatric eyes with cataracts, even before lensectomy. Future study is warranted to evaluate the role these structural differences may play in the development of glaucoma following cataract surgery and the significant variation in how individual glaucoma eyes respond to angle surgery.