Novel Technique to Improve the Efficacy of Corneal Cross Linking in Cases of Post LASIK Ectasia [Letter]

Dear editor

We read “Novel Technique to Improve the Efficacy of Corneal Cross Linking in Cases of Post LASIK Ectasia” by Yousif et al.¹ This paper describes a topography-guided photorefractive keratectomy (TG-PRK), followed by phototherapeutic keratectomy (PTK) and corneal cross-linking (CXL) for post-LASIK ectasia (PLE).

The authors discuss our novel under-flap CXL (ufCXL) technique for treatment of PLE.² In ufCXL, the LASIK flap is opened, retracted, protected, and the exposed corneal stromal bed is soaked with riboflavin. Excess riboflavin is irrigated away, the flap is repositioned, and ultraviolet light is administered to the surface.² They state

Along a relatively short follow-up period of 6 months, and including a small cohort of eight eyes, the study results showed stability (with no improvement) of each of CDVA, efficacy index, safety index, K max, and corneal irregularity index

Yet they omit our updated long-term ufCXL outcomes published in August 2022 in the Journal of Refractive Surgery.³ The study reports on 20 eyes confirming stabilization of PLE at 3 years with maintenance of visual outcomes. Refractive astigmatism statistically decreased from 0.83 D pre-ufCXL to 0.55 D post-ufCXL (P = 0.04), and maximum keratometry from 42.4 to 42.0 D (P = 0.04), without excimer laser ablation.³

In reference to our preliminary ufCXL results, Yousif et al state “no regularization of the corneal surface is achieved” with the ufCXL technique. They suggest that without adding TG-PRK ablation, “no improvement” of PLE occurs, only stabilization . However, ufCXL was devised exclusively for early PLE. That is why our mean pre-treatment Kmax was 10 D lower vs the Yousef study (42.4D vs 53.1D). The intent of the ufCXL technique is not to reduce astigmatism or refraction, but rather to stiffen the cornea early in the ectatic process, which locks in the early PLE corneal changes that have had only a minor impact on vision. This eliminates the visual rehabilitation burden and loss of CDVA that can occur with POE. The authors performed their treatment in far more advanced PLE cases, where ufCXL was not indicated and has never been attempted. The benefit of a combined excimer CXL procedure vs CXL alone in moderate to advanced POE has been well documented in the literature.

In summary, this Letter underscores a wider debate of when to intervene and treat PLE. ufCXL has the potential to halt ectasia progression, preserve vision, and minimize irregular corneal astigmatism without the need for complex visual rehabilitation. The technique has minimal patient discomfort, recovery, and downtime. The potential of minimizing the significant detrimental effects of progressive POE, with early ufCXL intervention, highlights the need to follow post-LASIK patients on a regular basis. Additional details on ufCXL can be found in letters, articles, and a book chapter.^4–8 We appreciate the authors contribution and innovation towards managing PLE.