The combination of transepithelial phototherapeutic keratectomy (PTK) with accelerated corneal collagen crosslinking (CXL) seems to be an effective long-term treatment in patients with progressive pellucid marginal degeneration, a study in Cornea reports.

In this retrospective three-year study, Turkish researchers included 20 eyes of 15 patients with pellucid who were treated with PTK and accelerated CXL at their clinic. Investigators recorded visual acuity, refraction, topographic keratometry, pachymetry and aberrations pretreatment and at six, 12, 24, and 36 months after treatment to find both short-term and long-term results.

The investigators noted stabilization in visual acuity throughout the 36 months of follow-up.

Other study highlights included:

  • Cylindrical value was significantly lower during the follow-up, decreasing from 4.97D at baseline to 3.28D at 36 months.
  • The spherical equivalent value started to improve in six months and became statistically significant at the 24-month and 36-month visits, reaching a 4D difference from the baseline measurement.
  • A significant decrease in average keratometry readings was observed in all follow-up points, going from 47.12 at baseline to 46.27 at 36 months.
  • The maximum K value remained stable in all visits (64.30 at baseline, 62.27 at 36 months).
  • Central and minimum corneal thicknesses were significantly lower compared with the baseline throughout the follow-up.
  • Higher-order aberration, trefoil, coma and spherical aberration values remained stable during the follow-up compared with baseline.

Although postoperative spherical equivalent and cylindrical values significantly improved compared with the preoperative values, these results did not directly affect visual acuity levels, researchers noted in their paper. “However, we believe that the decrease in corneal irregularity could result in an increase in the comfort of patients’ contact lens usage.”

The researchers also reported keratometry values remained stable or improved during the 36 months of follow-up compared with the preoperative values. Additionally, average K significantly decreased in the first six months (about 0.5D), and this reduction continued gradually during the 36 months of follow-up with a total of 1D difference. Kmax decreased about 1D in the first six months, and the difference was about two diopters at the 36-month visit; however, it could not reach a statistically significant level, investigators added.

The study’s limitations include its retrospective-nature, small sample size, the lack of preoperative corneal epithelial map data and the absence of a control group. “Nevertheless, our study included quite a high number of patients with pellucid marginal degeneration compared with other studies in the literature, which can be attributed to the fact that true pellucid marginal degeneration is a very rare disease,” they added.

Further comparative studies with more patients are needed to confirm the findings regarding this challenging ectatic disorder, investigators said.

Cagil N, Sarac O, Yesilirmak N, et al. Transepithelial phototherapeutic keratectomy followed by corneal collagen crosslinking for the treatment of pellucid marginal degeneration: long-term results. Cornea. May 16, 2019 (E-pub, ahead of print).