CXL-LASIK reinforces cornea stability

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Performing collagen crosslinking as a concurrent primary LASIK procedure-show data from comparative studies of patients with hyperopia and myopia at risk for ectasia or regression postLASIK-increases postoperative refractive and keratometric stability.

By Cheryl Guttman Krader; Reviewed by A. John Kanellopoulos, MD

Athens, Greece-About 1 in 40 patients who present for laser vision correction of myopia to the private surgery center of A. John Kanellopoulos, MD, in Athens, Greece, have topographic evidence of keratoconus.

Considering the endemic nature of this disease in his patient population-together with evidence demonstrating the occurrence of long-term refractive regression after LASIK for hyperopia and high myopia-in 2007 Dr. Kanellopoulos introduced performing collagen crosslinking (CXL) concurrently with primary LASIK in all patients with hyperopia and myopia considered at risk for ectasia or regression.

He theorized that the addition of CXL would stabilize the cornea, and results from subsequent comparative studies demonstrate the combined procedure (known as LASIK-Xtra) is effective for increasing refractive and keratometric stability.

“Although not universally considered mainstay, LASIK-Xtra requires just 2.5 minutes of additional time following routine LASIK, and may provide reinforcement to the known inadvertent biomechanical change associated with standard LASIK,” said Dr. Kanellopoulos, medical director, Laservision.gr Eye Institute, Athens, and clinical professor of ophthalmology, New York University Medical College, New York.

Currently, Dr. Kanellopoulos performs LASIK-Xtra in patients with myopia exhibiting any of the following characteristics:

• Spherical error ≥–6 D.

• Age <30 years.

• Astigmatism >1.5 D.

• Intereye astigmatism difference ≥1 D.

The CXL procedure is performed following the excimer laser ablation. Being careful to protect the flap and hinge from riboflavin exposure, 0.10% saline-diluted riboflavin solution is applied directly onto the stromal bed, he said.

After a 60-second soak time, the flap is replaced and residual riboflavin removed by irrigation. Once the flap position is secured, the cornea is irradiated with the UVA light source using a fluence of 30 mW/cm².

Dr. Kanellopoulos is currently using an exposure time of 80 seconds.

“In contrast to epi-on CXL, a key concept here is to have minimal riboflavin present in the epithelium and flap stroma,” Dr. Kanellopoulos said. “Therefore, the UV light can penetrate through freely and interact with the underlying stroma soaked with riboflavin.”

Comparing outcomes

In a paper in press in Cornea, Dr. Kanellopoulos and colleagues report a comparison of outcomes in a consecutive cohort of 140 patients who underwent myopic femtosecond-LASIK with or without concurrent high-fluence CXL. Baseline data showed that compared to the controls having LASIK alone, the LASIK-Xtra eyes had higher cylinder (–1.35 versus -0.85 D), MRSE (–6.75 versus –5.33 D), and keratometry values (flat: 43.92 versus 43.15 D; steep: 45.15 versus 44.03 D).

However, the groups were otherwise well matched, as they were all operated on by Dr. Kanellopoulos using the same ablation zone, laser systems (topography-guided with the Alcon Refractive Suite), flap dimensions, and postoperative care regimen.

Data from long-term serial follow-up visits through 24 months demonstrated better refractive and keratometric stability in the combined procedure group. Between postoperative months 1 and 12, mean MRSE showed a slightly greater myopic shift in the LASIK only group compared with the LASIK-Xtra eyes (–0.27 versus –0.24 D). Mean keratometry in the flat and steep meridians increased by +0.57 D and +0.54 D in the LASIK only eyes but by only +0.03 D and +0.05 D in the LASIK-Xtra group.

At 1 year, uncorrected visual acuity outcomes were also significantly better in the LASIK-Xtra group.

“I am a strong advocate for evaluating keratometry following LASIK and not just visual acuity,” Dr. Kanellopoulos said. “There is a learning curve factor with Snellen acuity measurements, and in my opinion, they may not be objective enough in patients that are evaluated many, many times.”

Findings from a randomized trial using a contralateral eye-controlled design demonstrated the benefit of simultaneous CXL for improving long-term refractive and keratometric stability after hyperopic LASIK [Kanellopoulos AJ. Kahn J. J Refract Surg. 2012.28(11 Suppl):S837-40]. The study included 34 patients being treated for hyperopia or hyperopic astigmatism. Again, LASIK was a topography-guided ablation performed with the Alcon Refractive Suite.

Baseline mean MRSE and cylinder values were +3.15 and 1.20 D in the LASIK-Xtra group and +3.40 D and 1.40 D in eyes having LASIK alone. After a mean follow-up of 23 months, mean MRSE regression was significantly less in eyes treated with the combined procedure than in those receiving LASIK alone, +0.22 D versus +0.72 D, respectively.

A. John Kanellopoulos, MD

E: ajkmd@mac.com

Dr. Kanellopoulos is a consultant to Avedro and Alcon Laboratories.

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