Epithelial and stromal changes induced by intacs examined by three-dimensional very high-frequency digital ultrasound.
OBJECTIVE
To examine epithelial and stromal layers by three-dimensional very high-frequency (VHF) digital ultrasound scanning before and after implantation of Intacs (intracorneal ring segments [ICRS]).


METHODS
Three-dimensional scanning was performed in five eyes before and 3 months after Intacs insertion. Digital signal processing techniques provided high-resolution B-scan imaging and I-scan traces for high-precision (1-microm) three-dimensional pachymetry. Thickness maps of individual corneal layers were constructed of the epithelium, stroma, and full cornea before and after surgery. Difference maps for epithelium and stroma were produced to examine anatomical changes in the thickness profile induced in each layer and correlate these to refractive changes.


RESULTS
B-scan examination revealed stromal and epithelial anatomy anterior and adjacent to the Intac. Ring depth could be measured topographically. There was stromal lamellar displacement by the ring segments that produced a concave anterior stromal groove within an annulus central to the ring. Epithelial filling of this concavity was shown in three dimensions in such a way as to produce orthogonally asymmetrical flattening of the corneal surface, thus potentially accounting for induced astigmatism. Mapping of the central stroma demonstrated thickening, potentially also accounting for astigmatic changes ascribable to orthogonal asymmetry.


CONCLUSIONS
VHF digital ultrasound scanning provided imaging and three-dimensional thickness mapping of corneal layers, enabling anatomical evaluation of the changes induced in the cornea by Intacs.
Reinstein
D Z
DZ
Weill Medical College of Cornell University, New York, NY 10021, USA. DanReinstein@compuserve.com
Srivannaboon
S
S
Holland
S P
SP
D000328:Adult; D003319:Corneal Stroma / Q000000981:diagnostic imaging* / Q000601:surgery; D019781:Corneal Topography; D019573:Epithelium, Corneal / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000000981:diagnostic imaging* / Q000601:surgery; D010865:Pilot Projects; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D012029:Refraction, Ocular; D014463:Ultrasonography; D014792:Visual Acuity