BLOG: Post-refractive ectasia: Outcomes and expectations

ByZaina Al-Mohtaseb, MD

Fact checked byChristine Klimanskis, ELS

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Key takeaways:

• There are some differences in cross-linking in post-refractive ectasia vs. keratoconus.
• The ability to cross-link to stabilize the cornea and preserve vision in post-refractive ectasia is encouraging.

Post-refractive ectasia is very rare. The incidence is only about 0.1% per 100,000 eyes undergoing LASIK and less than that in eyes undergoing PRK or SMILE.

Post-refractive ectasia and keratoconus are histologically similar, particularly in terms of the anterior stromal findings, which include thinning of the stromal collagen lamellae and microstriae in the stromal bed. In fact, in some cases, it is difficult to determine if the patient would have developed keratoconus anyway or if there is a distinctly different disease process provoked by the corneal insult during refractive surgery. In many cases, however, post-refractive ectasia doesn’t disrupt the posterior corneal tissues as much as we would typically see in keratoconus.

The treatment for ectasia, whether post-refractive or due to progressive keratoconus, is the same: corneal collagen cross-linking. This year, Amaral and colleagues published a systematic review and meta-analysis of results from corneal collagen cross-linking for ectasia after refractive surgery. They reviewed 15 studies comprising 512 eyes of 421 patients and found that after cross-linking, patients with ectasia experienced stable uncorrected visual acuity, a significant improvement in corrected visual acuity, stable endothelial cell count, a decrease in Kmax and a significant decrease in central corneal thickness. Across all 15 studies, the only serious complication was one case of epithelial ingrowth beneath the LASIK flap.

This meta-analysis tells us that, as with cross-linking for keratoconus, we can expect excellent outcomes and a very good safety profile, but there are some differences to be aware of in treating post-refractive ectasia and in counseling patients with this condition.

First, epithelial removal must be handled more carefully in the presence of a LASIK flap. I use alcohol to remove the epithelium in all of my cross-linking cases, but in post-LASIK ectasia, I begin the debridement centrally and then carefully move in radial fashion out toward the flap edge. I am very careful to avoid getting any epithelium under the LASIK flap and also careful not to dislodge the flap. Cross-linking has a very low risk of complications generally, but the risk of an intraoperative flap complications in a post-LASIK patient is greater, and this must be discussed with the patient. A future FDA approval of epi-on cross-linking could be beneficial for this patient population, if the efficacy were similar to the current FDA-approved protocol of epi-off procedure performed with the iLink system (Glaukos).

Secondly, cross-linking of post-refractive ectasia patients seems to have slightly more variable efficacy than we expect with cross-linking for keratoconus. In the pivotal clinical trials for the iLink system, eyes with post-refractive ectasia achieved about half the flattening that was achieved in keratoconic eyes, or a mean decrease in Kmax of 0.7 D vs. 1.6 D from baseline to 1 year.

Finally, the risk of progression after cross-linking is higher in eyes with post-refractive ectasia. Studies in the U.S. and Europe have shown that about 90% of keratoconic eyes treated with cross-linking remain stable 10 years after treatment. However, there is some evidence of more variability in effect and higher risk of progression in eyes with post-refractive ectasia — although treated post-refractive ectasia eyes still fare much better than untreated eyes. Although I always emphasize the importance of regular eye exams after cross-linking, lifelong monitoring for progression is particularly important for post-refractive ectasia patients.

It is not entirely clear why cross-linking outcomes differ in post-refractive ectasia. There may be biomechanical changes or differences in riboflavin diffusion rates related to the presence of a LASIK flap, or there may be pathophysiologic mechanisms that are unique to post-refractive ectasia. We also must remember that most of what is known about treatment of rare ectasia comes from small studies of fewer than 40 eyes with limited follow-up. Nevertheless, the ability of cross-linking to stabilize the cornea and preserve vision in this population is encouraging.

References:

• Amaral DC, et al. Clin Ophthalmol. 2024;doi:10.2147/OPTH.S451232.
• Greenstein SA, et al. Eye Contact Lens. 2023;doi:10.1097/ICL.0000000000001018.
• Hersh PS, et al. Ophthalmology. 2017;doi:10.1016/j.ophtha.2017.03.052.
• Hersh PS, et al. Ophthalmology. 2017;doi:10.1016/j.ophtha.2017.05.036.

For more information:

Zaina Al-Mohtaseb, MD, director of research for Whitsett Vision Group and clinical associate professor of ophthalmology at Baylor College of Medicine in Houston, can be reached at zaina1225@gmail.com.

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