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Eyes with primary angle-closure glaucoma (PACG) have a higher maximum intraocular pressure (IOP) and thinner lamina cribrosa thickness (LCT) than those with primary open-angle glaucoma (POAG), according to a study published in Clinical Ophthalmology. The study also said all glaucomatous eyes had a thinner LCT than healthy control eyes, with maximum IOP inversely correlated to the LCT.
The comparative cross-sectional study, designed to compare the LCT between 34 patients with PACG, 38 patients with POAG, and 62 control group patients, used enhanced depth-imaging optical coherence tomography (EDI-OCT) to reach its findings. A single eye of each patient was tested. The LCT was determined at the center of the optic nerve head using EDI-OCT, with 9 points measured and averages analyzed.
Investigators found that significant differences between the PACG and POAG eyes, including maximum IOPs of approximately 32.5 mm Hg in PACG vs 25.05 mm Hg in POAG eyes, P =.001). Also, LCTs were significantly different between the 3 groups measuring 226.99 µm in the PACG group, 257.17 in the POAG group, and 290.75 μm in the control group (P <.001). In addition, LCT was correlated with mean deviation of the visual field (P =.001), and was inversely correlated with maximum IOP (P <.001).
Linear regression analysis revealed that LCT was inversely related to age (P =.008), female sex (P =.018), and maximum IOP (P =.002). LCT was marginally related to visual field MD (P =.053), investigators report.
Limitations of the study include that patients were recruited at a referral tertiary eye care in a cross-sectional manner, which meant that glaucomatous eyes were at such an advanced stage that investigators couldn’t know the trend of preglaucomatous thickness of lamina cribosa. Also, maximum IOP data came from hospital records and referral letters so might not have been correct. The small sample size might have introduced bias as well. Finally, researchers were unable to enroll matched IOP of POAG and PACG patients.
“This study supports the use of SD-OCT with EDI mode for detecting lamina cribrosa change,” investigators write. “The LCT was significantly thinner in the glaucoma (POAG and PACG) groups compared to control eyes, and we found that maximum IOP was inversely correlated to LCT, and PACG had a higher maximum IOP and thinner LCT than POAG. The pressure-dependent mechanism deformed the lamina cribrosa in which the higher IOP-loaded stress led to a greater lamina cribrosa strain.”
Reference
Wanichwecharungruang B, Kongthaworn A, Wagner D, Ruamviboonsuk P, Seresirikachorn K. Comparative study of lamina cribrosa thickness between primary angle-closure and primary open-angle glaucoma. Clinical Ophthalmol. 2021;15(2):697-705. doi:10.2147/OPTH.S296115.
