Corneal Cross-Linking:

Frequently Asked Questions

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Is corneal cross-linking (CXL) a new treatment for keratoconus?

Yes and No:

CXL was recently approved in the United States in April 2016 based on randomized clinical trials performed in the United States in 2008. However, CXL was introduced in Europe more than 15 years ago where the procedure was pioneered. There are many long-term studies that demonstrate the efficacy and safety of the procedure. Dr. Randleman was one of two surgeons to perform CXL in the FDA clinical trial that led to eventual approval of CXL for both keratoconus and post-LASIK ectasia.

 

What is the main goal of CXL?

The purpose of the treatment is to strengthen the cornea to prevent progressive bulging and thinning that can interfere with vision. With a stronger and more stable cornea the risk of requiring a corneal transplant is much lower.

 

What is the success rate of CXL?

The success rate at preventing progressive bulging and thinning is 98%. Additionally many patients have seen some modest regression of their corneal bulging, which can improve contact lens fitting success and for some patients provide better vision with glasses than they have been able to achieve before treatment.

 

Can CXL be repeated?

In rare cases (less than 2%) where CXL is not successful in stabilizing a cornea, a repeat treatment can be performed. Since very few patients have ever required repeat CXL less is known about the efficacy of this repeat treatment, but it does appear to be equally safe as initial treatments.

 

Is there an ideal age for CXL?

Usually, the younger the patient the greater the chance of preserving vision with CXL, but patients at any age may benefit from CXL, especially if they have worsening keratoconus (progression) or if they have difficulty with their current vision correction in glasses or contact lenses. Most patients treated have been between 10 and 60 years of age. With treatment, the corneal contour is preserved, and therefore it is best to have CXL when the shape is only mildly distorted. Patients with advanced disease can have CXL but the vision may be less than ideal with glasses or soft contact lens necessitating the use of a rigid contact lens.

 

Are some keratoconus patients not good candidates for CXL?

Patients must have satisfactory corneal thickness for the procedure to be performed. A thickness of 400 microns is required prior to the ultraviolet light application. Corneas with a thickness between 320 microns and less than 400 microns can usually be treated by using specialized hypotonic drops to swell the cornea to 400 microns or greater prior to the ultraviolet light application. Also, corneas with significant central scarring that interferes with vision are not good candidates for CXL

 

Can vision be improved with CXL?

Although the main goal of CXL is to stabilize the cornea, 60% of patients actually have a mild improvement in their vision. This is due to the fact that the corneal surface becomes less irregular with CXL as the steep areas are flattened and the flat areas are steepened.

 

How is the procedure performed?

The procedure is divided into 3 steps. Most patients find the procedure very easy and are comfortable. Anesthetic drops are instilled, which numbs the surface of the eye, and makes the procedure pain free. The first step of the procedure is the removal of the central corneal epithelium. The second part of the procedure is the instillation of specialized drops containing Riboflavin. Drops are typically used for 30 minutes. The third part of the procedure is the use of ultraviolet light, which is typically used for 30 minutes.

 

Why does the ultraviolet light treatment time vary from clinic to clinic?

The original treatment protocol in Europe was the use of ultraviolet light for 30 minutes at an energy level of 3mw/cm2.This is the only treatment protocol that is currently FDA approved in the United States, but some practitioners have used differing treatment protocols.

 

Can the corneal epithelium be left intact or does it have to be removed?

The long-term clinical studies have shown outstanding results when the epithelium is removed prior to CXL. To date there is no evidence that treatment is effective when the epithelium is left intact, but research is ongoing to see if these treatments can eventually be effective.

 

What is required after the treatment?

Immediately after the procedure a soft bandage contact lens is inserted and worn for approximately 5-7 days. This allows enhanced comfort and promotes healing of the corneal epithelium. An antibiotic drop and a steroid drop is used for the first 1-2 weeks after surgery. Artificial tears can be used as needed for comfort.

 

Is the vision better immediately after the procedure?

Usually the vision is slightly blurrier during the first month and then gradually improves. The blurred vision is related to the healing time of the corneal epithelium. Initially when the epithelium becomes intact it tends to be somewhat rough. With times it undergoes thickening and thinning in different areas to smooth the corneal contour.

 

How do I know if the treatment is successful?

Repeat corneal mapping is performed to demonstrate corneal stability or flattening. The mapping is typically performed at 3 to 6 months postoperatively and then annually. Sophisticated mapping techniques can evaluate both the front and back surfaces of the cornea to determine stability, improvement, or progression.

 

What are the potential complications of the treatment?

The complication rate is extremely low with CXL. The risk of infection is rare. In fact ultraviolet light can be used to kill bacteria and parasites in patients with corneal infections. Occasionally there is a delay in the healing of the corneal epithelium, which can delay the return of best vision, and in rare cases corneal haze may occur that could limit vision.

 

When can I start wearing contact lenses?

After the procedure it is best to wait at least 2 weeks before returning to contact lens wear. If you have never worn contact lenses and would like to start lens wear it is best to wait at least one month before a consistent refraction can be obtained and lenses fitted.