In comparison with spectral-domain OCT (SD-OCT), Pentacam OCT appears to significantly underestimate corneal thickness during the first few months following customized corneal crosslinking to treat keratoconus.
Study design
This was a retrospective study of 33 eyes with keratoconus that underwent customized corneal crosslinking that compared measurements taken by the Scheimpflug-based Pentacam high-resolution (HR) OCT and MS-39, an anterior-segment SD-OCT. Both devices were used to measure central corneal thickness, thinnest corneal thickness, and epithelial thickness preoperatively and at 1, 3, and 12 months after crosslinking.
Outcomes
Although preoperative measurements were similar for both Pentacam HR and MS-39, at postoperative months 1 and 3 Pentacam HR significantly underestimated corneal thickness. The SD-OCT alone demonstrated epithelial thickening at post-operative month 1.
Limitations
This study used a relatively small sample size and only investigated cases of customized corneal crosslinking, which may limit the applicability to other methods of treating keratoconus.
Clinical significance
Pentacam HR is one of the most highly utilized tools in the follow-up of keratoconus patients. This study highlights the natural history of Pentacam HR-derived corneal thickness measurements after crosslinking and emphasizes how they may underestimate true corneal thickness in the first few months after surgery, results that could be mistakenly considered indicative of progressive disease. Although this study only examined customized corneal crosslinking, postoperative haze formation is common after standard, full-fluence, epithelium-off crosslinking as well. With haze a likely reason for the skewed Pentacam HR measurements, it is possible these results could be extrapolated to traditional treatment methods as well. In addition, this study provides evidence of epithelial remodeling one month postoperatively.
Financial Disclosures: Dr. Uri Soiberman discloses financial relationships with Lions Eye Institute for Transplant & Research (Lecture Fees/Speakers Bureau); National Eye Institute, Research to Prevent Blindness (Grant Support).