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Sebastian E Siebelmann, Jens Horstmann, Manuel Marcel Hermann, Björn Bachmann, Claus Cursiefen, Philipp Steven; Microscope-integrated Intraoperative Optical Coherence Tomography Enables Real-Time Monitoring Of Corneal Structural Alterations During Collagen Crosslinking. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3376.
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© ARVO (1962-2015); The Authors (2016-present)
Corneal UVA-riboflavin collagen crosslinking (CXL) is a standardized and safe procedure for the treatment of keratoconus. The main complication is corneal decompensation due to endothelial cell damage after UVA irradiation. Standardized protocols prevent irradiation damage in most cases, but no intraoperative parameters exist for individual procedure surveillance e.g. depth of riboflavin penetration or progression in collagen crosslinking. Nonetheless the development of a hyperreflective zone in optical coherence tomography (OCT) imaging immediately after CXL is assumed to reflect riboflavin penetration depth. Here we demonstrate the real time acquisition of changes in corneal structural properties by intraoperative OCT (iOCT).
Prospective case series of seven patients (4 female, 3 male), who underwent CXL, using a commercially available 840nm Spectral Domain OCT (iOCT; OpMedT, Luebeck, Germany), adapted to an operating microscope (HS Hi-R Neo 900A, Haag Streit, Wedel, Germany). Underlying disease in all cases was Keratoconus. Increase of central and peripheral depth-dependent corneal hyperreflectance was observed in cross-sectional images of the cornea, selected from volume scans, which were acquired after corneal abrasion, after 30 minutes of riboflavin application and 15 and 30 minutes of UVA irradiation. For image analysis, a custom-made algorithm using Matlab-Environment evaluated time-dependent local changes in corneal reflectivity. Images taken prior to the treatment served as controls.
In all patients, a hyperreflective zone was visible during OCT imaging after riboflavin application and after 15 and 30 minutes of UVA irradiation. Depth and hyperreflectance, were progressive during the procedure. Reflectance was more intense in the corneal periphery then in the center.
iOCT enables online imaging and procedure monitoring during CXL. As the depth of a clearly visible and well evaluable hyperreflective zone while CXL is associated with riboflavin penetration depth, iOCT allows for individual penetration surveillance in real time. Nonetheless it has to be clarified, how the hyperreflective corneal zone allows for drawing conclusions regarding e.g. rigidity and arrangement of corneal collagen fibers. In the future, intraoperative OCT may allow for developing individual treatment protocols for CXL.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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