Keratoconus is a common condition of the cornea that affects approximately 1 in 1000 people. The cornea acts as the major focusing lens of the eye. The cornea is the clear dome of the eye made up of hundreds of layers that are linked to each other with collagen. In keratoconus, these collagen links may be deficient and this leads to progressive corneal thinning and stretching. The cornea can start to bulge forward causing an irregular cone shape (similar to a distorted football) and therefore affects how images are focused. Keratoconus normally affects both eyes, although at differing points of onset and rates of progression. In most people it usually starts as early as the teenage years and typically continues until the mid-30s. It is thought that there may be an inherited component to this condition.

Symptoms that you may have Keratoconus

During the early stages, keratoconus may be treated by wearing glasses to focus images. However, as the disease progresses, glasses are no longer sufficient to correct the distorted vision. Typically vision becomes impaired at all distances; night vision is usually worse. As well, patients usually develop a significant distortion of vision, with multiple images, streaking and sensitivity to light. Generally though, there no sensation of pain.

Diagnosis

The diagnosis of keratoconus can be made by an ophthalmologist or optometrist once a detailed eye exam has been performed. In very early cases, a clinical eye exam may not be sufficient. Usually these cases can be diagnosed with advanced corneal imaging using a corneal topographer or a Pentacam. In this situation, the image that is produced will reveal a characteristic steepness and irregularity of the cornea.

Treatment

Most patients with mild to moderate keratoconus can wear contact lenses to improve vision but others may experience contact lens intolerance of failure. Regardless, contact lenses do not treat the fundamental problem: progression of disease. With minimal options available, many of these patients required corneal transplantation.

Corneal collagen cross linking by ultraviolet light with riboflavin is the first treatment proven to help slow down the progression of keratoconus and sometimes improve the amount of astigmatism – even in its early stages. The success of this treatment is based on its ability to strengthen the abnormal stretchiness of the keratoconic cornea by increasing corneal stiffness and rigidity. It has been used by eye surgeons in Europe for the past 10 years on hundreds of patients and the device we use has been approved by Health Canada. When corneal collagen cross linking is teamed together with other modalities such as Intacs corneal implants, ICL’s and laser reshaping of the cornea, it can help to prevent the need for a corneal transplant.

How is Collagen Cross Linking Done?

The treatment is performed on one eye at a time, although both eyes can be treated on the same day. The treatment is conducted under sterile conditions. The eye is frozen with drops and held open for you. The front covering layer of the cornea is removed and riboflavin drops are applied to the cornea for 30 minutes. After this, UV-A light is applied for another 30 minutes. At the end of the treatment a contact lens is placed over the cornea to aid in healing, and several drops are applied. The contact lens will be left in place for several days and you will continue with drops for several weeks. Over the following 2-3 days, that front covering layer on your cornea will regenerate. You will be given a prescription for pain medication which you may use over the first few days. There is often considerable discomfort on the first night. During this period, the eye may feel very dry and irritated. The vision will be very blurry at first but will improve gradually over several weeks.

How does Collagen Cross Linking halt the progression of Keratoconus?

Until recently, there has not been a proven treatment which could strengthen the cornea in patients with keratoconus. Although the welding of the fibers that occurs during the corneal cross linking procedure has little effect on the clarity of the cornea, it has been proven in many European studies to slow down and even halt the progression of keratoconus. The procedure itself is simple: vitamin B2 is applied to the cornea, followed by exposure of the cornea to ultraviolet light for a short time. The light activates molecules called free radicals that act to weld adjacent fibers in the cornea, much like a coiled electrical wire. This process is similar to the one used in the creation of many of our modern polymers that are used to make many household plastics. It is also similar to the bonding procedure that dentists use to attach materials, such as those used in fillings, to our teeth. The whole process takes about one hour.

What are the Benefits to C3R?

About 2/3 of all patients treated with collagen cross linking and riboflavin drops will have improved vision and in some cases mild regression of the steepness of their cornea. Compared with the untreated eye, collagen cross linking has been shown to slow the progression of disease in all patients. Also, unlike contact lenses, collagen cross linking can stop the progress of disease and may even cause regression of disease. These results are permanent and do not involve injections or stitches. It is a relatively simple, single – one hour treatment with quick recovery times and long-lasting results. Most importantly, it serves as an alternative to corneal transplantation – a far more invasive procedure than C3R or Intacs Corneal rings and thus should be considered only after exploring all options.

It is important to note that this collagen cross linking does not restore the cornea to a completely normal shape (similar to a soccer ball or football). Glasses and contact lenses will still be required and further treatment may be needed. In some cases, the treatment is not completely effective and the progression of the keratoconus may not be halted.

What are the risks of the treatment?

Very few risks have been reported to date. The dose of the ultraviolet light is designed to prevent damage to the cells that line the back of the cornea and other structures of the eye.

1. There have been no reports of cataracts, glaucoma or retinal injury to date.
2. A transient self limited haze will be seen in almost all patients after treatment. Usually this resolves after 6-12 months and is not visually significant.
3. Transient edema which is self limited may occur but usually resolves once the epithelium has healed.
4. The treatment may effect the measurement of intraocular pressure in the future.
5. There has been 1 case report of Diffuse Lamellar Keratitis which resolved with appropriate treatment.
6. There has been 1 case report of Herpes simplex keratitis which resolved with appropriate treatment.
7. It may not be effective and other forms of treatment will later be needed.

Patients will experience some discomfort which typically subsides within the first week. Some patients may not be able to wear their contact lenses for several weeks after the treatment. A new contact lens fitting may be required as well as a change in prescription.

As with any treatment, there may be long term risks which have not yet been identified. The increased corneal rigidity may wear off over time and further treatments may be required.