Comparing Change in Anterior Curvature After Corneal Cross-linking Using Scanning-slit and Scheimpflug Technology

• Published in: American journal of ophthalmology Vol. 191; pp. 129 - 134
• Main Authors: Lang, Paul Z., Thulasi, Praneetha, Khandelwal, Sumitra S., Hafezi, Farhad, Randleman, J. Bradley
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2018; Elsevier Limited
• Subjects: Adult; Cornea - pathology; Corneal Pachymetry - instrumentation; Corneal Topography - instrumentation; Cross-Linking Reagents - pharmacology; Equipment Design; Female; Follow-Up Studies; Humans; Imaging, Three-Dimensional; Keratoconus - diagnosis; Keratoconus - drug therapy; Male; Medical imaging; Ophthalmology; Photochemotherapy - methods; Prospective Studies; Reproducibility of Results; Software; Tomography; New York; United States > US; Switzerland
• ISSN: 0002-9394; 1879-1891
• DOI: 10.1016/j.ajo.2018.04.018

To evaluate the correlation between anterior axial curvature difference maps following corneal cross-linking (CXL) for progressive keratoconus obtained from Scheimpflug-based tomography and Placido-based topography. Between-devices reliability analysis of randomized clinical trial data. Corneal imaging was collected at a single-center institution preoperatively and at 3, 6, and 12 months postoperatively using Scheimpflug-based tomography (Pentacam; Oculus Inc, Lynnwood, Washington, USA) and scanning-slit, Placido-based topography (Orbscan II; Bausch & Lomb, Rochester, New York, USA) in patients with progressive keratoconus receiving standard protocol CXL (3 mW/cm2 for 30 minutes). Regularization index (RI), absolute maximum keratometry (K Max), and change in K Max (ΔK Max) were compared between the 2 devices at each time point. Fifty-one eyes from 36 patients were evaluated at all time points. Values were significantly different at all time points (56.01 ± 5.3 diopters [D] Scheimpflug vs 55.04 ± 5.1 D scanning-slit preoperatively [P = .003]; 54.58 ± 5.3 D Scheimpflug vs 53.12 ± 4.9 D scanning-slit at 12 months [P < .0001]) but strongly correlated between devices (r = 0.90–0.93) at all time points. The devices were not significantly different at any time point for either ΔK Max or RI but were poorly correlated at all time points (r = 0.41–0.53 for ΔK Max, r = 0.29–0.48 for RI). At 12 months, 95% limits of agreement were 7.51 D for absolute K Max, 8.61 D for ΔK Max, and 19.86 D for RI. Measurements using Scheimpflug and scanning-slit Placido-based technology are correlated but not interchangeable. Both devices appear reasonable for separately monitoring the cornea's response to CXL; however, caution should be used when comparing results obtained with one measuring technology to the other.