Comparison of central topographic maps from a swept-source OCT biometer and a Placido disk-dual Scheimpflug tomographer.

PURPOSE: To compare central topography (CT) from IOLMaster 700 with predicate topographic (PT) maps from a Placido disk-dual Scheimpflug tomographer in detection of irregularities that would influence the decision-making for implanting premium intraocular lenses (IOLs) (toric, multifocal, or extended depth-of-focus). SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas. DESIGN: Prospective comparative case series. METHODS: Eyes with various corneal conditions were randomly selected: regular/irregular corneas, previous corneal refractive surgery, and keratoconus or pellucid marginal degeneration. Three observers compared the CT and PT maps and answered a questionnaire for each eye. The questionnaire focused on (1) overall shape similarity between CT and PT and (2) decision-making for premium IOL implantation based on CT and PT. Answers to the questionnaire and agreement in answers among observers were evaluated. RESULTS: The study included 105 eyes. Comparing CT and PT, similar shape was observed in 68.6% to 89.5% of cases, and comparable map symmetries were reported in 60.0% to 83.8%; the same decision regarding premium IOL implantation was made in 75.2% to 97.1% of cases. There were significant interobserver agreements among 3 observers for all questions, with Fleiss κ values ranging from 0.141 to 0.450 (all P < .05). Peripheral corneal steeping or flattening was the primary finding that was visible on PT but not on CT. CONCLUSIONS: Compared with the PT, CT provided similar overall shape and comparable symmetries in most cases. The same decision was made whether to recommend a premium IOL based on CT and PT in 75% to 97% of cases.

Role of the corneal epithelium measurements in keratorefractive surgery.

PURPOSE OF REVIEW: Refractive surgery has stimulated considerable progress in corneal and anterior segment imaging, and optical characterization of the eye. From front surface corneal topography, we evolved to three-dimensional corneal tomography with limbus to limbus characterization of the front and back corneal surfaces and pachymetric mapping. Corneal anatomical evaluation has further evolved to layered or segmental tomography with the ability to characterize corneal epithelial thickness profile and the elevation of stromal front surface. Further characterization of even more specific structures, such as Bowman's layer and Descement's membrane, has been also demonstrated. The applications of such understanding in keratorefractive surgery are reviewed. RECENT FINDINGS: Understanding the corneal epithelial profile is of interest in many areas of ophthalmology, especially in refractive surgery. The most relevant applications include screening candidates at higher risk for complications (i.e. progressive ectasia and tear dysfunction syndrome), planning primary procedures, enhancements, and therapeutic surgery, and also postoperatively understanding the wound healing and clinical outcomes. SUMMARY: Corneal epithelial thickness was first available using digital very-high-frequency ultrasound. Advances in anterior segment optical coherence tomography enabled such fundamental evaluation, which accelerated progress. Such knowledge significantly impacts safety and efficacy of refractive surgery, and also allows for significant improvement for therapeutic procedures. VIDEO ABSTRACT.