Eyecare professionals use all of the necessary tools to preserve the vision of patients who have corneal ectasia. GP contact lenses (often scleral lenses) are the first line of defense for patients exhibiting signs of irregular astigmatism, corneal thinning, and scarring. These lenses may provide adequate vision for diseased corneas, but it is only a matter of time before corneal steepening worsens and a new lens or a corneal transplant is necessary.
Corneal cross-linking (CXL) is the only procedure that increases the cornea’s collagen connections to slow down or even halt further progression of corneal ectasia. The goal of CXL is to prevent the necessity of a corneal transplant in the future (American Optometric Association, 2016).
CXL was approved by the U.S. Food and Drug Administration in April 2016 for progressive keratoconus and post-laser-assisted in situ keratomileusis (LASIK) ectasia. CXL is a minimally invasive procedure, but it is not free of complications. The most common include punctate keratitis, corneal striae, corneal epithelial defects, and eye pain. Diffuse lamellar keratitis, stromal scarring, and significant corneal haze are less common (Jankov et al, 2010).
Improvement may be evident in as little as one week, but it usually takes several months to several years to reach the desired outcome. Clinical trials have shown an average of 1.7D of flattening of the central apex one year after CXL (Hersh et al, 2010).
A 35-year-old male reported decreased vision—right eye more so than left eye—at his visit to the University of Missouri-St. Louis (UMSL) College of Optometry in November 2015. He was first seen at the UMSL College of Optometry in 1999, at which time he was diagnosed with keratoconus. He had previously worn both small-diameter and intralimbal lenses for his condition. He was then fit into scleral lenses (OD in 2012 and OS in 2014). At the November 2015 visit, his corrected visual acuity was 20/30+ OD and 20/40– OS. Figure 1 shows his corneal topography OD. He was then referred for a surgical consult for CXL.
The patient returned to the UMSL Clinic in April 2016, four months after the procedure. Figure 2 shows his post-CXL corneal topography OD. He was fit once again into scleral lenses. Over the next two months, some minor modifications were made to improve both the fitting relationship and vision, resulting in good patient satisfaction. His final visual acuities were 20/25 OD and 20/30+ OS.
Although CXL stops further progression of corneal ectasia, leads to flattening of the central cone, and can improve visual acuity, GP lenses—in this case, scleral lenses—are needed to achieve optimal vision. Scleral lens fitting after CXL is usually easier because the cornea is less irregular in shape (Karpecki and Schectman, 2011). Modifications to pre-operative lenses are often necessary to achieve the best visual and fitting outcome, but it is evident that the combination of CXL and scleral lenses can often be a successful one. CLS
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Dr. Leonhardt is currently completing the cornea and contact lens residency program at the University of Missouri-St. Louis College of Optometry.
Dr. Bennett is assistant dean for Student Services and Alumni Relations at the University of Missouri-St. Louis College of Optometry and is executive director of the GP Lens Institute. You can reach him at email@example.com.