Intraoperative changes in corneal structure during excimer laser phototherapeutic keratectomy (PTK) assessed by intraoperative optical coherence tomography
Excimer laser phototherapeutic keratectomy (PTK) is a safe treatment for superficial corneal opacities, e.g., in corneal dystrophies or degenerations. Nevertheless, no standardized treatment protocols are available and intraoperative monitoring was not possible, so far. Here we evaluate the potential benefits of the intraoperative assessment by microscope-integrated intraoperative optical coherence tomography (MI-OCT) of corneal optical properties during PTK.
Retrospective study of eight patients (one male, seven females; age range, 43–80 years, mean = 66.1 years) using an 840-nm microscope-integrated spectral-domain OCT (iOCT; OptoMedical Technologies, Luebeck, Germany adapted to HS Hi-R Neo 900A, Haag Streit Surgical, Wedel, Germany). Images were acquired before and after corneal abrasion and after PTK. For PTK, a SCHWIND Amaris 750S excimer laser (SCHWIND eye-tech-solutions GmbH und KO. KG) was used. Parameters assessed were the central corneal thickness (CCT), changes in central depth-dependent corneal tissue intensity (TI), and corneal surface roughness (SR) in cross-sectional images of the cornea.
Intraoperative monitoring using microscope-integrated OCT was possible in all patients at all time points. TI of the anterior corneal stroma decreased significantly (p = 0.037) after PTK (T1 = 15.1 ± 3.6, T2 = 15.0 ± 3.84, T3 = 13.7 ± 3.38), but not after corneal abrasion alone, indicating increased transparency caused by excimer laser PTK. CCT was significantly lower after corneal abrasion (p = 0.017), but not after PTK (T1 = 630.4 ± 70 μm, T2 = 544.1 ± 59.4 μm, T3 = 558.3 ± 52.5 μm. SR significantly decreased (p = 0.043) after PTK (T1 = 614.4 ± 37.5 pixels, T2 = 634.4 ± 35.6 pixels, T3 = 611.0 ± 40.3 pixels).
Intraoperative OCT allows real-time imaging during PTK and the assessment of corneal optical transparency and its surface roughness. It has to be clarified in larger studies if these parameters correlate with later postoperative visual outcomes.
KeywordsPTK Corneal dystrophy Excimer laser Surface treatment Intraoperative optical coherence tomography
We thank Mrs. J. Austin for native language check.
Study concept, design: Siebelmann, Cursiefen.
Data collection/measurements: Siebelmann, Scholz, Hermann.
Analysis and interpretation of data: Siebelmann, Scholz, Matthaei, Bachmann, Horstmann, Cursiefen.
Drafting of the manuscript: Siebelmann, Scholz, Cursiefen.
Critical revision of the manuscript for intellectual content: Siebelmann, Scholz, Horstmann, Bachmann, Cursiefen.
Administrative, technical or material support: Siebelmann, Horstmann, Cursiefen.
Sebastian Siebelmann and Claus Cursiefen had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Compliance with ethical standards
Conflict of interest
All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (Ethics committee of the University Hospital of Cologne, File number 1 and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
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