Superficial Keratectomy Without Mitomycin C In Degenerative Corneal Diseases– Long Term Refractive Outcome, Haze And Higher Order Aberrations

Degenerative corneal surface diseases such as peripheral hypertrophic subepithelial corneal degeneration (PHSCD) and Salzmann nodular degeneration (SND) can significantly reduce visual acuity and lead to abnormal refractions. The cause is largely unclear. In addition to laser phototherapeutic keratectomy, these findings can be treated by simple manual dissection, so called superficial keratectomy.  This is sometimes performed with Mitomycin C as a recurrence prophylaxis. There is insufficient evidence for this treatment, side effects like corneal melting are possible. We report the long-term results of this method without the use of Mitomycin C.

This retrospective study was conducted in accordance with the declaration of Helsinki and approved by the local ethics committee of the University of Rostock. Patients, that underwent superficial keratectomy from 2019 to 2021, were identified and included. The data was then anonymized and analyzed.

The refraction and the best-corrected visual acuity was determined and a Scheimpflug topography was performed using a Pentacam (Oculus Wetzlar). After informed consent superficial keratectomy was performed under local anesthesia. Postoperatively, a bandage contact lens was applied and preservative-free ofloxacin drops and tear substitutes were administered five times per day. After epithelial closure, the contact lens was removed and the cornea then treated with dexamethasone eye drops 5 times daily, which were reduced weekly depending on the findings. Follow-up with refraction, BCVA and Scheimpflug tomography was performed. Densitometry was also evaluated.

 could be included. All patients were female. The mean age was 58 +/- 15 years (26-83). The last examination took place after a mean of 27 +/-5 months (19-40). There was a significant increase in visual acuity (before-surgery 0.4 +/-0.31 logMAR to 0.19 +/-0.27 logMAR post-surgery, p = 0.004). Densitometry showed no significant differences in the anterior 120 μm, stroma and posterior 60 μm. The higher order aberrations (HOA) showed a significant decrease in the 6 mm zone (pre-surgery: 5.52 +/- 2.6, post-surgery: 2.24 +/- 1.8, p = 0.014) as well as the maximum radius of curvature Kmax (pre-surgery 52.9 +/-9.8, post-surgery 47.7 +/- 4 dpt., p = 0.026). The spherical equivalent showed no significant change. No adverse effects were recorded.

Superficial keratectomy without mitomycin C was shown to be a safe and effective procedure for visual acuity improvement in the patient population studied. The lack of a significant change in densitometry can possibly be explained by the stratified evaluation performed here. A zonal evaluation will follow and may then show differences. The mean visual acuity could be improved significantly, after a mean of 27 +/- 5 months there were no recurrences affecting the visual acuity in the long-term course, which would have resulted in the necessity of a re-operation.