Intraoperative optical coherence tomography to evaluate the effect of the eyelid speculum on corneal pachymetry during accelerated corneal cross-linking (9 mW/cm2)

Abstract

PurposeTo investigate intraoperative anterior segment optical coherence tomography (AS-OCT) to compare pachymetry changes between two methods (group 1: speculum-on, group 2: speculum-off during riboflavin instillation stage) during corneal cross-linking /CXL) (9 mW/cm for 10 min) in keratoconic patients.MethodsIn this interventional case series, 11 eyes (11 patients) in group 1 and 14 eyes (14 patients) in group 2 were enrolled. Pachymetry measurements by spectral domain OCT was performed at baseline, after epithelial removal, after 30 min of imbibition with riboflavin, and after UV irradiation. Repeated measures analysis of variance was used to compare the trend of changes in different stages of the procedure within and between two groups.ResultsThe corneal thinnest pachymerty (CTP) at baseline, after epithelial removal, 30 min of riboflavin instillation, and irradiation was 469.8±26.5, 438.0±27.1, 354.3±28.4, 367.1±31.8 microns in group 1 and 463.2±25.1, 438.0±27.1, 421.6±54.0, 386.9±34.0 microns in group 2, respectively. Group 1 showed a significantly greater decrease in the corneal pachymetry (P<0.001) during riboflavin instillation, while in group 2 a greater decrease in CTP was observed during the UV irradiation phase (P=0.002).ConclusionsUsing the intraoperative OCT, the speculum-off group had a more stable corneal pachymetry during riboflavin instillation time. Despite this, the effect was not lasting throughout the procedure; significant changes were noted in the corneal pachymetry at the end of operation in both groups; further highlighting the limitations imposed by corneal stromal shrinkage using isotonic dextran containing riboflavin solution for CXL.

Intraoperative OCT for Monitoring Corneal Pachymetry during Corneal Collagen Cross-Linking for Keratoconus

“…As shown in the Figures 1 and 2, the speculum-off group had a more stable corneal pachymetry value during riboflavin instillation. On the other hand, the speculum-off group had a greater decrease in the corneal pachymetry value during the irradiation phase, further highlighting the limitations imposed by corneal stromal shrinkage using the isotonic dextran containing riboflavin solution for CXL [25].…”

Clinical applications for intraoperative optical coherence tomography: a systematic review

“…Several studies reported successful use of OCT to measure corneal thickness and/or corneal dissection depth during CXL and refractive surgery [94,95]. Compared to the current gold standard for measuring corneal thickness, ultrasound pachymetry, OCT pachymetry has several advantages.…”

Intraoperative Optical Coherence Tomography Imaging in Corneal Surgery: A Literature Review and Proposal of Novel Applications

“…Mazzotta and Caragiuli [ 60 ] reported the use of i OCT during corneal cross-linking and recommended intraoperative optical pachymetry evaluation before starting UV-A irradiation. Ghaffari et al [ 61 ] and Pahuja et al [ 62 ] also reported the use of i OCT or MIOCT during corneal cross-linking to evaluate the corneal pachymetry during the surgery. Kobayashi et al [ 63 ] used MIOCT not for surgery but for evaluation of donor cornea tissues through the viewing chamber.…”