Domanda n. 23
The four smaller computerized videokeratographs (CVKs) shown on the left of the figure below are from a patient who has undergone automated lamellar keratoplasty (ALK). The large CVK on the right is from a patient who has undergone laser in situ keratomileusis (LASIK) for the correction of myopia


Left: Four CVKs showing central flattening over time following ALK.

Right: Single CVK showing central flattening following LASIK.

Which of the following statements about these CVK images is true?
 1 They demonstrate central corneal flattening in both patients.
 2 They demonstrate equal irregular astigmatism in both patients.
 3 Decentration is demonstrated in the ALK CVK, and excellent centration is demonstrated in the LASIK CVK.
 4 Evidence of epithelial ingrowth is demonstrated in the LASIK CVK.



Central corneal flattening can be obtained by lamellar techniques using both ALK and LASIK. LASIK, as seen in this CVK, causes central corneal flattening similar to ALK, although it is associated with less irregular astigmatism. The irregular astigmatism is less because the laser is capable of producing a more regular refractive "cut." Decentration of the ablation zone can occur with LASIK but is not seen in these images. Epithelial ingrowth can lead to irregular astigmatism which is easily seen on CVK. Irregular astigmatism is not noted in either of the CVK images.