The purpose of this article was to evaluate the results of combined aspheric wavefront-guided transepithelial Excimer laser photorefractive keratectomy (PRK) and phototherapeutic keratectomy (PTK) to correct aberrations and refractive errors after radial keratotomy (RK) or keratoplasty.
The first Excimer laser refractive-therapeutic surgeries were simple cylindric ablations to correct severe, disabling astigmatism after keratoplasty, although substantial regression limited the effectiveness. The technique evolved to the more effective photorefractive keratectomy (PRK) and then laser in situ keratomileusis (LASIK). The correction of classic ametropia (myopia and astigmatism) after penetrating keratoplasty using PRK is less effective and less predictable than PRK for naturally occurring myopia and astigmatism, and corneal haze and refractive regression are more prevalent.
Current refractive-therapeutic surgery uses topography-guided custom corneal ablations for irregular corneal astigmatism after keratoplasty. Two-step procedures, such as phototherapeutic keratectomy (PTK) followed by custom PRK or LASIK with the lamellar cut followed by ablation, have been proposed, as has wavefront-driven custom ablation based largely on corneal topography-derived wavefront analysis. Another option is simultaneous custom transepithelial PRK with PTK, which combines the refractive effect of PRK and the therapeutic effect of laser-assisted epithelial removal.
The approach mentioned in the article here to correct aberrations and refractive errors after RK is sequential PRK using a corneal wavefront-guided aspheric ablation followed by removal of epithelium in the center or periphery of the treated area using a defined epithelial thickness profile and PTK without masking fluid. The present study evaluated the feasibility and results of this technique.
The article did mention that although performing laser treatment on an unstable cornea could lead to dehiscence in the future, it is important to balance the advantages of a fast and easy procedure with the possible risk for a variation in astigmatism post-operatively. It is believed that other than placing a new corneal transplant, the proposed simultaneous PRK-PTK technique is the only option in these cases.
All of the test patients had a 6-month follow-up and even though no nomogram adjustments were made, no eye required retreatment. However, it was noted that a study with a longer follow-up and larger number of eyes is needed to confirm the stability of the treatment. In addition, there was only 1 case of haze (trace) in this study. This was believed to be because of the application of MMC before the ablations.
In summary, simultaneous corneal wavefront-guided transepithelial PRK and PTK using an Excimer laser was safe and effective in correcting aberrations and refractive errors after RK or keratoplasty. The visual, optical, and refractive results were good; astigmatism decreased to subclinical values postoperatively in the RK group and to moderate values in the keratoplasty group, and there was a significant decrease in HOAs, which affect contrast sensitivity. These findings indicate that simultaneous corneal wavefront-guided transepithelial PRK and PTK might be the technique of choice to correct refractive errors and aberrations after RK or keratoplasty.