Identification and Quantitative Assessment of Schlemm's Canal in the Eyes with 360° Angle Recession Glaucoma

SYNOPSIS: Angle recession, trabecular meshwork injury, increased trabecular pigmentation, and reduced Schlemm's canal dimensions can cause reduced aqueous outflow and unilateral glaucoma in an eye, following blunt trauma. Also, these patients are possibly at a risk to develop raised intraocular pressure (IOP) in the normal fellow eye due to reduced Schlemm's canal area. AIM: To identify and quantitatively evaluate Schlemm's canal (SC) parameters by anterior segment optical coherence tomography (AS-OCT) in the patients with unilateral 360° angle recession glaucoma (ARG) and compare with the fellow normal eyes and age-related normal control. MATERIALS AND METHODS: Six patients with a history of unilateral ocular blunt trauma and unilateral 360° ARG, normal fellow eyes and 34 age-matched normal controls underwent anterior chamber angle imaging with corneal line scan protocol using AS-OCT. Schlemm's canal cross-sectional area (SC-CSA) and meridional and coronal diameters were measured on temporal and nasal sections at 3 and 9 o'clock positions. RESULTS: In the AS-OCT cross-sectional images, SC was observed as a horizontally oval or ellipsoidal translucent space. The mean SC-CSA (1,710 ± 376.1 μm(2) vs 6,100 ± 2,700 μm(2), p < 0.0001), mean meridional diameter (243.6 ± 55.47 μm vs 474 ± 125.6 μm, p < 0.0001), and mean coronal diameter (32.68 ± 6.27 μm vs 57.42 ± 16.27 μm, p < 0.0001) of the SC were smaller in ARG eyes when compared with the normal eyes. The SC dimensions were reduced in the untraumatized fellow eyes of ARG patients when compared with the normal eyes (SC-SCA: 2350 ± 602.1 μm(2), p = 0.001, meridional diameter: 341.8 ± 88.8 μm, p = 0.012 and coronal diameter: 31.67 ± 3.8 μm, p < 0.0001). There was no difference in the measured SC dimensions between the ARG eyes and the normal fellow eyes. CONCLUSION: The reduced SC parameters in the eyes with unilateral 360° ARG and the normal fellow eyes could mean that these patients probably have an underlying structural abnormality in the SC. Trabecular meshwork injury, angle recession, and increased trabecular pigmentation are probably the predisposing factors in the ARG eyes for the increase in IOP. Whether the normal fellow eyes develop IOP rise in the future needs to be seen during regular follow-up. HOW TO CITE THIS ARTICLE: Mansoori T, Reddy AA, Balakrishna N. Identification and Quantitative Assessment of Schlemm's Canal in the Eyes with 360° Angle Recession Glaucoma. J Curr Glaucoma Pract 2020;14(1):25–29.