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 infuence 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 com bined bulbar conjunctival and Tenon's layer thickness was measured 3 mm above the superior limbus. Conjunctival and Tenon's layers appeared as a hyper-refective section as opposed to the hypo refective underlying sclera. Measurements were taken using the inbuilt review software.Results: The age ranged from 23 to 91 years. There were 20 mal e s and 28 females. The mean conjunctival and Tenon's layer thick ness 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 infuence 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.How to cite this article: Howlett J, Vahdani K, Rossiter J. Bulbar Conjunctival and Tenon's Layer Thickness Measurement using Optical Coherence Tomography. J Curr Glaucoma Pract 2014;8(2):63-66.

Effect of the outer stent position on efficacy after minimally invasive transscleral glaucoma gel stent implantation

“…As shown by Howlett et al. (), Tenon's layer in the OCT appears as a hyperreflective section as opposed to the hyporeflective section underlying the sclera. The conjunctival stroma in OCT consists of irregular fibres, perfused blood vessels and cystic spaces and therefore appears more irregular (Howlett et al.…”

“…The OCT is capable of distinguishing Tenon's layer from the stromal layer of the conjunctiva and therefore shows the position of the stent after the implantation (Howlett et al. ).…”

“…The conjunctival stroma in OCT consists of irregular fibres, perfused blood vessels and cystic spaces and therefore appears more irregular (Howlett et al. ). The assignment to a group was done blinded without the knowledge of the actual IOPs or number of medication.…”

“… Intraconjunctival implantation: (i) Tenon's layer below the outer stent lumen in OCT (Howlett et al. ), (ii) obvious superficial implant position in OCT due to a very superficial stent position without tenting of Tenon's layer, and (iii) fluid‐filled spaces underneath the outer lumen of the stent in OCT without fluid on top of the implant indicating a superficial implant position. Intra‐ and subtenon implantation: (i) none of the above criteria fulfilled, (ii) Tenon's layer on top of the outer stent lumen in OCT (Howlett et al. ), and (iii) lack of fluid‐filled spaces underneath but fluid on top of the outer lumen of the stent in OCT indicating a deep implant position. …”

“…; Howlett et al. ). Postoperatively, the final position of the outer lumen of the XEN‐GGM can be either near the sclera (intra‐ and subtenon) or more superficially (intraconjunctival).…”