Aim: To assess the long term (1 year) effect of myopic and hyperopic LASIK on corneal sensation and innervation. Methods: 83 eyes of 43 patients having LASIK were evaluated. According to the preoperative spherical equivalent, the eyes were divided into three groups: group 1, myopia from 20.75 to 26.00 D; group 2, myopia from 26.25 to 211.50 D; and group 3, hyperopia from 1.25 to 5.00 D. Corneal sensation was measured and in vivo confocal microscopy (IVCM) was done at the central cornea before, and at 1 month, 3 months, 6 months, and 1 year after LASIK. Results: The mean corneal sensation in group 1 was greater than in groups 2 and 3 at all postoperative measurements. The difference between group 1 on one hand and groups 2 and 3 on the other hand was statistically significant at 1 month and 3 months after LASIK and was not statistically significant afterwards. IVCM study of 27 eyes revealed that the number and length of nerve fibre bundles in the sub-basal region decreased after LASIK and was significantly lower at all times after surgery despite the return of corneal sensation to preoperative level. Conclusion: After LASIK, central corneal sensitivity is decreased for as long as 6 months or more. The results suggest that lamellar cutting of the cornea during LASIK impairs corneal sensitivity and is related to the ablation depth. The diameter of ablation too may contribute to this drop in sensitivity. The return of corneal sensations does not directly correlate with the regeneration of nerve fibres as determined by confocal imaging. Sensations return to normal values before complete restoration of normal innervation if this indeed ever occurs.

Alcohol delamination of the corneal epithelium before PRK or LASEK consistently results in a very smooth cleavage at the level of the hemidesmosomal attachments, including the superficial lamina lucida. It leaves behind a very smooth surface, which is ideal for PRK. It also allows for an intact epithelial flap to be lifted as a sheet from the corneal surface and hence is ideally suited for the LASEK technique.

LASIK re-treatment for residual myopia, by lifting the original flap, is an effective option. Refractive results are fairly predictable, and refraction stabilises by 3 months after re-treatment. Lifting the corneal flap after cutting the epithelium on the flap edges is easy to perform and has a very low incidence of epithelial ingrowth.

PURPOSE: To evaluate whether agreement or disagreement between the axis of astigmatism as determined by refraction and corneal topography has any influence on the outcome of laser in situ keratomileusis (LASIK) correction of astigmatism. METHODS: Charts of 122 consecutive eyes of 75 patients (46 women and 29 men) who underwent uncomplicated, primary LASIK for myopic astigmatism were reviewed. The series was divided into two groups - group 1, "agreement" (77 eyes) with a difference between refractive and topographic axis of astigmatism =sl5°, and group 2, "disagreement" (45 eyes) with a difference >15°. RESULTS: The mean difference in axis of astigmatism was 10°±17.20° (range: 0° to 86°), and 63.11% of eyes were within a 15° difference. A significant negative correlation was found between the percentage of corrected astigmatism and the degree of disagreement. The percentage of corrected astigmatism differed significantly between the two groups (P=. 002) with better results in group 1 (agreement). CONCLUSIONS: Disagreement between refractive and topographic astigmatic axis is common. Approximately one third of eyes with astigmatism have >15° disagreement. Disagreement between refractive and topographic determination of the astigmatic axis can be considered a prognostic factor for LASIK correction of myopic astigmatism. [J Refract Surg. 2005;21:269-275.]

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