Anterior and posterior corneal changes after crosslinking for keratoconus.
OBJECTIVE
To evaluate anterior and posterior changes in corneal topography and tomography after corneal crosslinking (CXL) in eyes with progressive keratoconus.


METHODS
Scheimpflug analyses (Pentacam, Oculus) of 20 eyes with keratoconus performed before and after corneal CXL were included into retrospective analysis. Mean follow-up was 2 years. Changes in topographic, tomographic, and pachymetric values were statistically analyzed applying analysis of variance. Further, the distance and direction between the anterior maximum keratometry (K(max)) and the apex as well as the distance and direction between the thinnest point in corneal thickness (TPCT) and the corneal apex before and after CXL were studied.


RESULTS
Two years after CXL, a statistically significant reduction of the keratometry at the flat meridian (-0.8 D, p < 0.05), the steep meridian (-0.5 D, p < 0.05), the "index of surface variance" (-5.3, p < 0.05), and the "index of highest decentration" (-0.05, p < 0.05) could be demonstrated. While the elevation of the front surface at the apex decreased (-1.5 μm, p < 0.05), the back elevation at the apex (+2 μm, p < 0.05) increased. Although not reaching statistical significance, the maximum front and back elevation demonstrated the same trend; while maximum front elevation data remained stable (-0.3 μm, p = 0.961), maximum back elevation data increased (+6.7 μm, p = 0.122). The corneal thickness at the apex (-22.0 μm, p < 0.001) and the TPCT (-20.0 μm, p < 0.001) decreased, leading to an increase of the corneal thickness progression from the corneal apex to the periphery. The position of K(max) and TPCT remained stable.


CONCLUSIONS
Corneal topography proved to be useful in the follow-up for CXL because of significant changes in the keratometry. Increasing posterior elevation values, despite a stabilized anterior corneal surface, might be a sign of ongoing ectatic changes in the posterior corneal surface.
*MD †BSc(Optom) ‡MD, PhD Department of Ophthalmology, UKE - University Medical Center Hamburg-Eppendorf, Hamburg (JS, MA, AF, FF, TK, SJL); Fielmann Academy 'Schloss Plön', Plön (AR); and Care-Vision Germany, University Medical Center Hamburg-Eppendorf, Hamburg, Germany (TK, SJL).
Johannes
J
Steinberg
Mariam
M
Ahmadiyar
Anika
A
Rost
Andreas
A
Frings
Filip
F
Filev
Toam
T
Katz
Stephan J
SJ
Linke
D000293:Adolescent; D000328:Adult; D003094:Collagen / Q000378:metabolism; D003315:Cornea / Q000473:pathology*; D063171:Corneal Pachymetry; D003319:Corneal Stroma / Q000378:metabolism; D019781:Corneal Topography; D003432:Cross-Linking Reagents / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D012189:Retrospective Studies; D012256:Riboflavin / Q000627:therapeutic use; D041623:Tomography, Optical Coherence; D014466:Ultraviolet Rays; D055815:Young Adult
D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin