Epithelial thickness after hyperopic LASIK: three-dimensional display with Artemis very high-frequency digital ultrasound.
OBJECTIVE
To characterize the epithelial thickness profile in a population of eyes after LASIK for hyperopia or hyperopic astigmatism.


METHODS
The epithelial thickness profile was measured in vivo by Artemis very high-frequency (VHF) digital ultrasound scanning (ArcScan Inc) across the central 10-mm diameter of the cornea on 65 eyes at least 3 months after hyperopic LASIK using a 7-mm ablation zone with the MEL 80 excimer laser (Carl Zeiss Meditec). Maps of the average, standard deviation, minimum, maximum, and range of epithelial thickness were plotted. The cross-sectional hemi-meridional epithelial thickness profile was calculated using annular averaging. Linear regression analysis was performed to evaluate correlations between epithelial thickness, spherical equivalent refraction treated, and maximum simulated keratometry.


RESULTS
The mean thinnest epithelial thickness was 39.7 +/- 5.6 microm and the mean thickest epithelial thickness was 89.3 +/- 14.6 microm. The average epithelial thickness profile showed an epithelial doughnut pattern characterized by localized central thinning within the 4-mm diameter zone surrounded by an annulus of thick epithelium, with the thickest epithelium at the 3.4-mm radius. The epithelium was on average 10-microm thicker temporally than nasally at the 3.4-mm radius. Central epithelium was thinner and paracentral epithelium was thicker for higher hyperopic corrections and steeper maximum simulated keratometry.


CONCLUSIONS
Three-dimensional high-resolution ultrasound mapping of epithelial thickness profile after LASIK for hyperopia demonstrated thinner epithelium centrally and thicker epithelium paracentrally. Presumably, the paracentral epithelial thickening compensated in part for the stromal tissue removed by the hyperopic ablation, whereas the central epithelial thinning compensated for the localized increase in corneal curvature.
Reinstein
Dan Z
DZ
London Vision Clinic, London, United Kingdom. dzr@londonvisionclinic.com
Archer
Timothy J
TJ
Gobbe
Marine
M
Silverman
Ronald H
RH
Coleman
D Jackson
DJ
D000328:Adult; D000368:Aged; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery; D019781:Corneal Topography; D004847:Epithelial Cells / Q000000981:diagnostic imaging; D019573:Epithelium, Corneal / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006801:Humans; D006956:Hyperopia / Q000503:physiopathology / Q000601:surgery*; D021621:Imaging, Three-Dimensional; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008875:Middle Aged; D009929:Organ Size; D012029:Refraction, Ocular / Q000502:physiology; D012189:Retrospective Studies; D014463:Ultrasonography; D014792:Visual Acuity / Q000502:physiology