ABSTRACT
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 µm2 vs 6,100 ± 2,700 µm2, 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 µm2, 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.
ABSTRACT
PURPOSE: To image and quantitatively evaluate the Schlemm's canal (SC) dimensions in the eyes with acute primary angle closure (APAC) with anterior segment optical coherence tomography (AS-OCT), and compare it with the SC measurements taken after the control of intraocular pressure (IOP) and in the normal age-matched controls. MATERIALS AND METHODS: Seventeen eyes of 14 patients with the newly diagnosed APAC and 59 age-matched normal subjects underwent AS-OCT to image SC. SC cross-sectional area, SC meridional and coronal diameters were measured in the temporal and nasal regions at 3 and 9 o'clock position. After laser iridotomy and control of the IOP, all SC parameters were measured again at a week later, in APAC eyes. Intrasession intraobserver reliability of the SC measurements was assessed with intraclass correlation coefficient. RESULTS: Mean SC-SCA (10,600 ± 2691 µm2), SC meridional (682 ± 125 µm) and coronal diameters (21.2 ± 8.2 µm) showed a significant increase in the APAC eyes at presentation, when compared to the SC parameters measured at a week later (6499 ± 1754 µm2, 450 ± 169 µm and 15.75 ± 8.6 µm, p = < 0.0001, < 0.0001 and 0.01, respectively) and in the normal controls (7192 ± 1022 µm2, 499.2 ± 179.8 µm, 15.43 ± 4.35 µm, p = 0.02, < 0.0001, 0.01, respectively). There was no difference in the measured SC parameters between the normal controls and APAC eyes, when the parameters were measured at a week, after resolution of the acute attack (all p > 0.05). CONCLUSION: A significant expansion of SC was observed in the APAC eyes at presentation, when compared to the normal controls and after the acute attack resolved. SC parameters may provide a useful research tool for evaluating morphological changes in the SC in APAC eyes, during an acute attack.