Does corneal cross-linking (CXL) actually work in corneal thinning disorders in which ectasia is present? This is a question that many of us have asked ourselves, and this single case might provide some insight.

Our patient is a 43-year-old female who underwent bilateral laser-assisted in situ keratomileusis (LASIK) surgery in 2013. Postoperatively, she developed bilateral corneal ectasia (Figure 1). Her uncorrected visual acuities were 20/400 OD and OS due to the presence of high irregular astigmatism. With diagnostic scleral lenses, her best-corrected visual acuities (BCVAs) were right eye 20/25 and left eye 20/25. Her post-LASIK central corneas were not significantly thin, measuring 552µm in the right eye and 512µm in the left. Scleral lenses were ordered for the patient, and she did extremely well with the comfort and vision of the lenses. Scleral lenses were ordered, and the patient did extremely well with the comfort and vision of the lenses.

Figure 1. Right and left eye corneal topographies pre-CXL and PRK.

A few months after the dispensing of the scleral lenses, the patient expressed interest in going to Canada to undergo bilateral CXL (at that time, the procedure was not FDA approved in the United States). Our university physicians agreed to assist in her post-CXL follow-up care.

A Risky Combination

The patient underwent the CXL procedure; however, unbeknownst to us, the surgeon and patient had decided that a simultaneous photorefractive keratectomy (PRK) would be performed to correct the patient’s myopic refractive error.

The patient presented to our clinic for her five-day post-surgical follow-up visit with moderate corneal haze, some ultraviolet-induced diffuse staining, and vertical epithelial healing lines in both eyes. Corneal topography revealed reduced ectasia with some residual corneal astigmatism in both eyes (Figure 2). However, her uncorrected visual acuities were right eye 20/25 and left eye 20/20–.

Figure 2. Right eye and left eye difference display maps pre- and post-CXL and PRK.

For the past two years, we have continued to follow this patient. Today, her central corneal thicknesses are right eye 400µm and left eye 458µm (Figure 3). Surprisingly, her uncorrected visual acuities have remained stable throughout the day at right eye 20/20 and left eye 20/20.

Figure 3. Right eye optical coherence tomography pre-CXL and PRK (top) and post-CXL and PRK (bottom). Note the central corneal thinning of the post-surgical image.

Needless to say, undergoing combined CXL and PRK would seem to be a risky proposition in any individual who has post-LASIK ectasia. The PRK is sure to result in further thinning of the already ectatic corneas, and there are few reports in the literature describing outcomes of this combined procedure.

A Possible Answer

Now back to our original question: Does CXL actually work? Time will tell whether or not this patient’s post-CXL corneas are “strong enough” to remain stable following a corneal thinning procedure like PRK. CLS