While Collagen Cross-Linking (CXL) is not yet approved by the FDA, hundreds of peer-reviewed journal articles have been published that have proven the safety and efficacy of the procedure. CXL has been approved in every country in the world other than the United States. The main indications for Collagen Cross-Linking are:
• Halt the progression of keratoconus
• Halt the progression of corneal ectasia following Laser Vision Correction (LASIK and PRK)
• Improve the shape of the cornea in a patient with stable keratoconus
It is sometimes difficult to determine if a patient is having disease progression when they are able to wear rigid contact lenses with good visual acuity. It is easier to detect progression of disease if the patient is not wearing rigid lenses by measuring changes in the Max K (steep K). Since it is not practical to have our patients not wear their lenses, I personally believe that the following categories of patients should have Collagen Cross-Linking:
• All patients with a new diagnosis of keratoconus
• All patients who have keratoconus and are in their teens, twenties and thirties, since most patients in these age groups experience disease progression
• Patients with stable keratoconus who have poor quality of vision or a difficult time tolerating contact lens wear
Early intervention in patients who are in the first two categories will frequently save them from a life of discomfort with rigid contact lenses and poor vision with lenses. Just because we can fit a cornea successfully with a contact lens with good vision does not mean that the cornea should not be cross-linked. Some patients can have rapid progression of disease that is never reversible. These periods of rapid progression of disease are frequently associated with periods of intense eye rubbing due to seasonal allergies.
Observing the progression of the patient’s disease and continuing to fit them with contact lenses is a disservice to the patient.
We can halt the progression of their disease and frequently improve the shape of their cornea by decreasing the astigmatism and myopia. This change in shape can frequently be substantially augmented by INTACS. Patients typically are able to wear contact lenses more comfortably with better quality of vision and perhaps the chance to go to soft toric lenses or spectacles.
INTACS result in a significant improvement in the shape of the cornea with improved regularity and a decrease, sometimes dramatic, in myopia and astigmatism. Most patients with keratoconus have asymmetric disease. Since both eyes have the same genetic makeup, both eyes should be cross-linked.
If you do not have corneal topography in your practice, the best way to diagnose early keratoconus is by using your manual keratometer. If the mires do not coincide with each other, it is likely that the patient has early keratoconus. A corneal topography can be performed to make the diagnosis. Other potential signs that may be consistent with early keratoconus that should increase the index of suspicion are:
• Oblique astigmatism
• Progression of astigmatism
• Irregular retinoscope reflex (scissoring or teardrop-shaped reflex)
• Decreased best corrected vision with no other obvious reason
• Corneal signs such as Fleischer’s ring or Vogt’s striae (more advanced signs)
Most of the patients I’ve seen have very advanced disease and are “at the end of their road” with contact lenses. This is frequently because CXL has not been available until recently. These are often patients who can be well served with a corneal transplant. CXL and INTACS will improve the shape of these corneas, however, if we were able to intervene with CXL and INTACS much earlier in their disease cycle, we could have saved these patients many years of struggle with contact lenses.
The study we are conducted has two arms – ‘epithelium on’ and ‘epithelium off’. The cornea heals very much the same as in PRK. Early on, the cornea may become steeper and thinner, however with time, typically by 6 months, the cornea is flatter and more uniform.