Removal of epithelium and scraping the underlying stroma as treatment for photorefractive keratectomy overcorrection or undercorrection of myopia.

BACKGROUND AND OBJECTIVE

A minority of patients who undergo excimer laser photorefractive keratectomy are overcorrected to the extent that they are symptomatic; they tend to be "poor healers" with little post-excimer subepithelial haze and a thinned epithelial layer. The reverse situation can also occur where "aggressive healing" results in undercorrection, excessive haze and a thickened epithelial layer.

PATIENTS AND METHODS

Overcorrection was treated in 19 eyes by removal of the corneal epithelium overlying the treated cornea with a disposable number 15 scalpel blade under topical anesthesia at the slit lamp. The exposed stroma was gently abraded with the blade in order to create inflammation and the laying down of tissue to partially resteepen the cornea. Eight eyes with undercorrection had "hyperplastic epithelium" removed with the number 15 blade. The intention was to abrade underlying subepithelial haze only if it was felt that a plaque of "haze" could be removed by so doing; in fact, no plaques were removed and it was difficult to remove the epithelium without associated trauma to the superficial stroma.

RESULTS

The mean refraction of the overcorrected eyes was +2.77 diopters (D) compared with +0.68 D at 12 months post-scraping. This can be contrasted with -3.11 D prior to scraping, and -4.67 D at 12 months for the undercorrected eyes. The only difference that could be detected between the overcorrected and undercorrected eyes was that the mean pre-excimer refraction of the overcorrected patients was -5.68 D, whereas that of the undercorrected patients was -8.22 D. It was not possible to predict which overcorrected eyes would do well after scraping.

CONCLUSION

Scraping is a very effective treatment of overcorrection after photorefractive keratectomy. Scraping as a treatment of undercorrection should not be undertaken.