Epithelial thickness mapping as an adjunctive tool for keratoconus screening

Session Details

Session Title: Imaging I

Session Date/Time: Monday 12/09/2016 | 14:30-16:30

Paper Time: 15:24

Venue: Hall C2

First Author: : G.Carp UK

Co Author(s): :    D. Reinstein   T. Archer                 

Abstract Details

Purpose:

To show illustrative examples of the application of epithelial thickness mapping as an adjunctive tool for keratoconus screening when combined with front surface corneal topography and corneal tomography.

Setting:

London Vision Clinic, London, UK

Methods:

Keratoconus screening was performed in 1,532 consecutive patients considering laser refractive surgery at the London Vision Clinic using the Atlas front surface corneal topographer, the Pentacam corneal tomographer (including Belin-Ambrosio enhanced ectasia analysis, BAD-D) and the Artemis Insight VHF digital ultrasound scanner (ArcScan Inc) to obtain layered corneal pachymetry maps including epithelial thickness. Example cases were identified to illustrate the different uses for epithelial thickness maps.

Results:

Case-1: there was 1.8D inferior steepening on topography and back surface apex was eccentric, but BAD-D was -0.29 indicating a normal cornea. Epithelial thickness mapping showed a normal pattern of thicker epithelium inferiorly, confirming the diagnosis by tomography. Case-2: topography was normal, back surface apex was slightly eccentric, and BAD-D was 1.25 indicating a normal cornea, but epithelial thickness mapping showed a localised region of epithelial thinning coincident with the eccentric back surface apex, indicating keratoconus. Case-3: there was 1D inferior steepening on topography and BAD-D was 4.38 indicating definite abnormality. However, the epithelium was thicker inferiorly, excluding keratoconus. Case-4: topography, tomography, and epithelial thickness profile were all normal, however this eye developed ectasia 7 years after LASIK for -6.25D.

Conclusions:

The use of a combination of topography, tomography, and epithelial thickness appears to provide the most sensitive method of screening for keratoconus. In cases where a front surface topography would have been indefensible in isolation, tomography and epithelial thickness mapping can confirm or exclude the presence of keratoconus. Epithelial thickness provides enhanced specificity as there can be cases where epithelium excludes keratoconus despite both topography and tomography indicating definite keratoconus. However, there are some cases that appear normal on all measurements that develop post-LASIK ectasia, i.e. ectasia without a cause.

Financial Disclosure:

... has significant investment interest in a company producing, developing or supplying product or procedure presented, ... receives consulting fees, retainer, or contract payments from a competing company