Bulbar conjunctival and tenon’s layer thickness measurement using optical coherence tomography

Abstract

Purpose: Observations made during glaucoma filtering surgery (trabeculectomy) suggest variability in the thickness of the bulbar conjunctiva and Tenon’s layers between individuals. We propose that this could influence the final bleb morphology and function. We designed a pilot study to assess this using optical coherence tomography (OCT) to measure bulbar conjunctival and Tenon’s layer thickness. Materials and methods: A total of 67 eyes of 48 individuals were scanned using an optovue Mode RT100 version 2.0 OCT machine. Cross-line CAM-L scans were taken and the combined bulbar conjunctival and Tenon’s layer thickness was measured 3 mm above the superior limbus. Conjunctival and Tenon’s layers appeared as a hyper-reflective section as opposed to the hyporeflective underlying sclera a. Measurements were taken using the inbuilt review software. Results: The age ranged from 23 to 91 years. There were 20 males and 28 females. The mean conjunctival and Tenon’s layer thickness was 393 ± 67 microns (mean ± SD) ranging from 194 to 573 microns. Conclusion: Optical coherence tomography conjunctival and Tenon’s layer thickness measurements appear to vary significantly between individuals. We postulate that this could influence the final bleb morphology and may predict the risk of bleb encapsulation and failure or thin avascular blebs. Further assessment could establish cut-offs on which patients should receive intraoperative antimetabolites and/or Tenon’s layer excision.