Corneal tomographic features of postrefractive surgery ectasia

Abstract

The purpose of this study was to evaluate the tomographic features of postrefractive surgery eyes. This was a retrospective evaluation of clinical data. Three patients with post-LASIK (laser-assisted in situ keratomileusis) and two patients with post-SMILE (small incision lenticule extraction) ectasia were imaged with Scheimpflug imaging (SI, Pentacam) and optical coherence tomography (OCT, RTVue). Curvature and wavefront aberrations of the air-epithelium interface (A-E) and epithelium-Bowman's layer interface (E-B) were derived. OCT of normal and keratoconic eyes from an earlier study were compared with the data of the ectasia eyes. Curvature and aberrometry of the A-E interfaces were statistically similar between SI and OCT. However, OCT revealed a steeper and more aberrated E-B interface than A-E though correlation between them was inferior to the correlation for keratoconic eyes. Furthermore, the magnitude of differences between the A-E and E-B interfaces was greater in the ectasia eyes than the keratoconic eyes. OCT could possibly assist better in selecting appropriate treatment plan for postrefractive surgery ectasia eyes than conventional tomographers.

Ectasia After Corneal Refractive Surgery: A Systematic Review

“…1). SMILE-Search results for post-SMILE ectasia resulted in 4366 articles, of which 4356 were excluded, yielding 10 articles [161][162][163][164][165][166][167][168][169][170]. In total, 19 eyes were reported to have ectasia related to SMILE.…”

Bowman's topography for improved detection of early ectasia

“…Thus, the topography of the Bowman's layer could be considered as a surrogate marker of early ectasia. Bowman's layer topography also showed differential surface features of postrefractive surgery ectasia, which could potentially improve the distinction between the surgery induced ectasia and natural progression of ectasia . Following were the salient outcomes of this study: Accurate classification of normal eyes was comparable between Pentacam and OCT. In VAE‐NT eyes, random forest accurately classified most of the eyes as normal since they had normal topography features, for example, the ratio of LOA of A‐E to E‐B was ~1 in both normal and VAE‐NT eyes. FFKC was classified best by OCT E‐B, and OCT A‐E and E‐B combined compared to Pentacam.…”

“…Thus, the topography of the Bowman's layer could be considered as a surrogate marker of early ectasia. Bowman's layer topography also showed differential surface features of postrefractive surgery ectasia, which could potentially improve the distinction between the surgery induced ectasia and natural progression of ectasia [15]. Following were the salient outcomes of this study:…”

Phase retardation and corneal sublayer thickness repeatability using ultrahigh-resolution polarization-sensitive OCT

“…In our previous work, we had hypothesized that the status of the stroma (such as shape and structure) could be a useful measure to evaluate the progression of disease and the detection of subclinical keratoconus. 29,30 We showed the changes in phase retardation in human corneas over a wide range of thicknesses comprising healthy, thin (<500 mm), and clinically suspect corneas. 31 We provided some evidence that the use of PS-OCT may significantly enhance the identification of subclinical disease in corneas with healthy and low thickness (less than 500 mm).…”