CORNEAL CROSS LINKING

 

What is Keratoconus?

 

Keratoconus is a progressive, non-inflammatory thinning of the cornea. The cornea becomes conical in shape with resultant loss of vision. The onset of the condition is usually in puberty and is progressive until the early twenties.

The cornea is the clear front window of the eye through which the light enters. Most of the focusing occurs at the cornea and is critical for normal vision. The cornea consists of five separate tissue layers; the epithelium (the thin tissue forming the outer layer), Bowman’s membrane, stroma, Descemet’s membrane and endothelium.

In keratoconus, the corneal tissue weakens from changes in the corneal collagen structure (ectasia). The weakening of the cornea leads to protrusion, astigmatism, loss of visual acuity and finally to the perforation of the cornea. The progression of corneal ectasia is often monitored for a period of 6 months by a series of corneal examinations. If there is evidence of quick progression at the first examination the procedure can be done to prevent further progression/worsening of the eye disease.

Treatment

 

In the early stages of keratoconus, spectacles or contact lenses can improve vision. As the condition worsens with increasing irregularity of the cornea and scarring, a corneal transplant becomes necessary. These options address the visual aspect of the condition and not the weakening of the corneal collagen structure.

In the late 1990 cross linking (CXL) was developed in Germany and widely used in Canada, Europe and Asia. The procedure utilizes riboflavin (vitamin B-2) drops and low-dose ultraviolet A light to create chemical bonds (crosslinks) that bind corneal collagen fibers together. These additional crosslinks in the clear corneal tissue strengthen and stabilize it by holding the fibers together and making it more solid and resistant to ectasia. The aim is to slow down or prevent further corneal ectasia and thus reduce the possibility for a corneal transplant.

Numerous international studies have shown that CXL can increase the human cornea’s strength and rigidity by 300%.

The aim of corneal crosslinking is not to improve the vision, but to stabilize it and to prevent further progression/worsening of Keratoconus.

Most studies have reported a stabilization of the keratoconus. The evidence indicates that 12 months, after the procedure the corneal curvature decreases by an average of 1.5 diopters in 100% of keratoconic eyes that have been treated, compared to a progressive increase in curvature by 1.3 diopters in eyes that have not been treated. This data provides compelling evidence that the treatment is effective.

About half of eyes that have undergone cross-linking also achieve improvement in their corrected vision. In up to 60% of patients an improvement in best spectacle-corrected vision of at least 1 line on the Snellen vision chart can be observed (2.3). In some patients, uncorrected vision has improved by 3 lines (4). In the remaining patients, no improvement in vision was achieved.

Corneal cross-linking is also useful for ectasia of the cornea following LASIK surgery, for pellucid marginal degeneration and other corneal ectatic disorders.

Advantages

 

• Improvement of corneal profile
• Improved visual acuity
• Increased corneal stability
• Increased biomechanical strength of the cornea
• Marginal increase in the thickness of the cornea
• Increase in the symmetry of the cornea
• Reduction of detoriating spectacle error
• Reduction of astigmatism
• Reduction of higher order aberrations (Corneal coma)

Candidates

 

Patients with corneal ectasia such as Keratoconus, corneal laser candidates with resulting unstable corneas after the procedure, corneal ulcers, corneal melting and other corneal pathologies can be assessed for CXL.

CXL: The Procedure

 

The progression of corneal ectasia is often monitored for a period of 6 months by a series of corneal examinations. If there is evidence of quick progression at the first examination, the procedure can be done to prevent further progression/worsening of the eye disease.

The procedure initiates the formation of cross-link which continues within the cornea for up 2 years after the procedure. The strength within the cornea improves. The riboflavin has a dual effect in that is absorbs the UVA and shields the interior of the eye, to create an increase in strength.

The procedure is performed as an outpatient procedure and mostly one eye is done per procedure. Please discuss with Dr Wassermann.

Omit from wearing eye make-up and wear comfortable clothes. You will be lying on a bed during the whole procedure.

Please take note that the ophthalmic assistant will be with you during the whole process. She will guide you during the whole process. Dr Wassermann will monitor the process with intervals during the procedure.

Process

 

A. A speculum is placed in the eye to keep the eye open.
B. Topical anesthetic drops are inserted into the eye.
C. The central most superficial layer (epithelium) of the cornea is debrided (6-8mm). This layer regenerates spontaneously with 3 to 5 days.
D. The corneal stroma is saturated with solution of riboflavin (vitamin).
E. The cornea is irradiated with ultraviolet rays for approximately 45 minutes.
F. A bandage contact lens is placed over the eye.
G. You will receive your script and a date for a follow-up appoint to see Dr Wassermann

After the Procedure

 

You will be given a script (eye drops and pain medication) to use after the procedure. The soft ‘bandage’ contact lens will remain in your eye until the surface has healed (about seven days). If the bandage lens falls out during this time, please throw it away – do not attempt to reinsert it.

The anesthetic drops will wear off later the day of your procedure, and your eye will be gritty, red and sensitive to light for several days. Everyone’s experience of pain is different, with some patients reporting very little discomfort and others describing the first few days as very painful. Your eyes could be light sensitive and many patients find sunglasses helpful.

Your vision will be quite blurred at first, but will clear gradually over the first few weeks.
It is normal to experience fluctuating pain within the first two days after surgery. However, if you experience increasing pain three or four days after the procedure this could be indicative of infection and you should contact the practice immediately. Please note that infection is rare, affecting fewer than 1% of patients.

What should I do, or not do, After CXL

 

Do not rub your eyes after the procedure; rubbing your eyes may cause progression of the Keratoconus and must be avoided.

A. It is important to put the eye drops in regularly as prescribed. You will be putting eye drops in every hour for the first day, and then every four hours for the following days.
B. Wash and shower normally, but try to avoid getting water in your eyes.

C. We will check your vision in the clinic the week after your procedure to confirm if your vision is good enough to drive. You can drive once you can read a number plate at 25 metres. Driving with good vision in only one eye is legal, but you should obviously exercise caution until you feel confident; start off by driving short distances by day in familiar surroundings.
D. It is normally safe to resume contact lens wear once the eye surface skin layer has healed. This typically happens around the end of the second week after your procedure.

E. Put an artificial tear drop in the eye if the eye feels itchy or irritated.
F. Other limitations on your activity for the first week include running, aerobics or gym exercises (in case of injury or sweat running into the eyes).
G. Do not use eye make up for a week after surgery.
H. You can drive once you can read a number plate at 25 metres. Driving with good vision in only one eye is legal, but you should obviously exercise caution until you feel confident; start off by driving short distances by day in familiar surroundings.
I. It is important to contact your ophthalmologist if you experience severe pain, increasing (rather than decreasing) redness of the eye or progressive worsening (rather than improvement) of vision after the surgery. DO NOT RUB YOUR EYES.

Do I need to take time off work or studies?

 

Yes. You should allow at least one week off while most of the surface healing occurs, or two weeks if your job involves a lot of computer work and the treatment is being done on your best eye.
Day to day activities such as watching TV or using a computer will not do any damage to your eye, but you might find it more comfortable to rest with your eyes closed early on.

What are the risks of CXL?

 

In general, CXL is very safe, but like all operations your eye needs time to heal and problems do occasionally occur:

A. Corneal infection.
B. Corneal inflammation.
C. Corneal haze: This causes visual “ghosting”, glare and halos, and blurriness especially in dim light. It occurs in up to 11% of cases in the first 3 months post-operatively. It usually resolves after 1 – 2 months, and has not been reported beyond 12 months.
D. Need for a repeat cross-linking treatment: More than one cross-linking treatment may be necessary, if the keratoconus is found to be progressing.
E. Recurrent corneal erosions.
F. Corneal scarring.
G. Without CXL treatment, at least 20% of all patients with keratoconus will eventually require a corneal transplant.

Conclusion?

 

Performing this procedure will most likely prevent the patient from requiring a corneal transplant in future and is thus very cost effective.

Cost

 

The relevant procedure codes include: 3138, 4985, 0004, 4986, 0202, 0201 bandage contact lense, 0201 Ribotran (Nappi code: 470568001), 3020 and 3036 per eye.
ICD10: H18.6.

The tariff code 3021 will be discharged for follow-up consultations in the first month. Normal consultations fees will be charged thereafter.

This practice will assist with a once-off motivation to your medical aid. It remains your responsibility liaise the authorization with your medical aid. Any additional reports requested by the medical aid will be for your payment.

Performing this procedure will most likely prevent the patient from requiring a corneal transplant in future and is thus very cost effective.

The patient is liable for direct payment of the above procedure to Dr Wassermann and arrangements must be made by the patient to claim the expense from your medical aid.