Because of the progressive nature of keratoconus, a two-pronged approach is needed to achieve the best treatment outcome possible. Corneal biomechanical stability is a priority; however, efforts must also be made to increase the patient’s functional vision. Intrastromal corneal ring segment (ICRS) implantation and laser-based corneal surface ablation coupled with corneal collagen crosslinking (CXL) are popular minimally invasive methods of improving both corneal biomechanical stability and optical inefficiency of the irregular cornea associated with keratoconus. Researchers have found that ICRS implantation, laser corneal ablation, and CXL can act synergistically to provide better visual outcomes when used in combination than alone.1
When three procedures are required to achieve the best outcome possible for a patient, optimizing convenience becomes a priority. If all the procedures are time-consuming, patient acquiescence is likely to be limited, irrespective of the final outcome predicted. CXL traditionally takes between 1.5 and 2 hours to complete, with 30 minutes of this time dedicated to ultraviolet-A (UV-A) light exposure. Recognition that the duration of this procedure can be significantly reduced simply by using a higher-energy light source has led ophthalmic experts to develop accelerated CXL (ACXL). This express form of CXL utilizes a higher-energy light (30 mW/cm2) than standard CXL, and thereby cuts UV-A exposure time to less than 3 minutes.
STUDY AND RESULTS
In 2012, my colleagues and I devised a small study to assess the efficacy and safety of simultaneous LASEK and ACXL in patients with early keratoconus and previous ICRS implants. Our study included six eyes of five patients with stage 1 or stage 2 keratoconus (mean age, 34 years). Four patients were male, one was female, and all had undergone femtosecond laser-assisted ICRS implantation with the Keraring (Mediphacos Ltda.) at least 1 year (mean, 25 months) prior to the start of the study. All eyes received LASEK-based corneal ablation using the Amaris 750S (Schwind eye-tech-solutions) followed by AXCL performed with the KXL System (Avedro, Inc.).
Each case required riboflavin soaking time of only 60 seconds after removal of the epithelium, followed by 75 seconds of UV-A irradiation. UCVA, BCVA, spherical and cylindrical refractive powers, and mean and maximum keratometry (K) all showed improvement at 3 months after LASEK plus ACXL. For example, the mean K measurement was 45.67 D prior to ICRS implantation; this improved to 43.08 D after ICRS implantation and further improved to 42.03 D after LASEK plus ACXL. BCVA was 0.61 logMAR prior to ICRS implantation, 0.75 logMAR after ICRS implantation, and 0.84 logMAR after LASEK plus ACXL. No postoperative complications were experienced during the follow-up period.
These encouraging results, albeit in a small patient group, demonstrate that this alternative approach to augmenting ICRS results holds promise for the future treatment of keratoconus. Because ACXL can be performed in a matter of minutes rather than the 1 to 2 hours currently dedicated to conventional CXL procedures, patient comfort and convenience are optimized with this new strategy.
CASE REPORT
A 28-year-old man presented for treatment of stage 2 keratoconus. He underwent femtosecond laser-assisted implantation of a single inferior ICRS (Keraring), and he achieved good refractive improvement postoperatively. UCVA improved from 0.01 logMAR before ICRS implantation to 0.60 logMAR after implantation, BCVA remained stable at 0.0 logMAR, spherical refraction improved from -2.50 D to -1.50 D, cylindrical refraction increased slightly from -2.00 D to -3.50 D, and maximum K (Kmax) improved from 48.60 D to 44.20 D.
Two years after ICRS implantation, the patient underwent corneal wavefront-guided LASEK (Keratron Scout; Optikon 2000 Industrie) and ACXL. This additional dual treatment further improved all refractive parameters so that, at 3 months post-LASEK and ACXL, the patient’s UCVA was 1.0 logMAR, BCVA was maintained at 0.0 logMAR, spherical refraction was plano, cylindrical refraction was plano, and Kmax was 43.50 D (Figure 1). The patient was happy with his visual outcome.
CONCLUSION
These results demonstrate that ACXL, when combined with LASEK, is a quick and effective method of further improving the visual outcomes of keratoconus patients who have been implanted with ICRSs. Given the progressive nature of keratoconus, it is important that the use of ACXL plus LASEK to augment the visual benefit of ICRS be made available to these patients as an option. If no attempt is made to strengthen and stabilize the cornea after ICRS implantation, disease progression may continue and prevent patients from reaping the full long-term benefits offered by ICRSs. Although longer follow-up is necessary to evaluate the stability of the good visual outcomes, my team and I have been encouraged by the results seen in our small group of study participants, and we look forward to larger-scale studies to shed more light on the outcomes of combined ICRS-ACXL-LASEK treatment in individuals with corneal ectasia.
Maria Clara Arbelaez, MD, practices at the Muscat Eye Laser Center, Muscat, Sultanate of Oman. Dr. Arbelaez states that she is a consultant to Schwind eye-tech-solutions. She may be reached at tel: +96 824691414; fax: +96 824601212; e-mail: drmaria@omantel.net.om.
- Kremer I, Aizenman I, Lichter H, Shayer S, Levinger S. Simultaneous wavefront-guided photorefractive keratectomy and corneal collagen crosslinking after intrastromal corneal ring segment implantation for keratoconus. J Cataract Refract Surg. 2012;38(10):1802-1807.
