Corneal cross-linking is a technique designed to treat progressive keratoconus and other conditions characterized by inherent corneal weakness and instability. This minimally invasive procedure uses eye drops and ultraviolet light to strengthen corneal collagen fibers. It is a safe procedure that may be an alternative to those who do not have to undergo corneal transplants.
Keratoconus is a condition where the cornea becomes thin and bulges out into a cone shape, resulting in blurred or distorted vision. It is a difficult condition to treat with eyeglasses or contact lenses. Cross-linking should not be used to treat keratoconus that has stopped progressing. Congenital keratoconus is progressive in young people but stabilizes in adulthood. It is also not recommended for people with thin corneas (thickness must be 400 microns and beyond) and infections (a prior herpes infection or other current infection).
Other reasons to avoid cross-linking include scars, dry eyes, and autoimmune diseases (due to risk of poor wound healing).
Also Known As
Preparation & Expectation Before Surgery
Cross-linking is a one-day, outpatient, office procedure that lasts about an hour. The patient will spend most of the day at the clinic after surgery.
Types, Purpose & Procedure
The two types of cross-linking include epithelium-off (Epi-off) and epithelium-on (Epi-on or transepithelial cross-linking). Epi-off removes the epithelium to enable easier access of riboflavin liquid into the deeper corneal tissue. Epi-on is less invasive and leaves the epithelium intact.
In cross-linking surgery, the surgeon relaxes the patient with mild sedation and uses anesthetic drops for numbing the eye. Some surgeons may also administer preoperative antibiotics to the patient. The patient stays awake and does not experience any discomfort.
- Scrapes away the eye’s epithelium
- Places riboflavin drops on the eye to allow diffusion into the cornea and weaken the corneal epithelial barrier. The surgeon gives drops at 1-5 minutes intervals for 15-30 minutes or until s/he can view riboflavin in the eye's anterior chamber on the slit-lamp examination.
- Uses an ultraviolet light for 30 minutes to activate the riboflavin, leading to bond formation and strengthening between the collagen fibers.
- Gives the patient antibiotic drops and places a bandage contact lens over the eye to protect it and help in healing.
Risks, Side Effects & Complications
Corneal cross-linking is associated with fewer risks and complications. However, as it involves the removal of the epithelium, it may be accompanied by risks that include:
- Corneal epithelial defect (surface cell disruption)
- Endothelial damage, though rare. The surgeon waits for about three months before doing a transplant.
- Sterile inflammatory infiltrates and infection due to the opening of the epithelium. The surgeon treats both with steroids and antibiotics respectively.
- Cross-linking failure which happens when the corneal disease continues to progress. The surgeon waits for six months to a year before repeating the procedure.
- Delayed epithelial healing which is one of the chief risks that leave the cornea open to other problems. Bandage contact lenses and autologous serum can speed up the healing.
- The epithelial haze which may begin about three weeks following surgery but will go away on its own in approximately six months. Since it's mild, most patients don't even notice it. The surgeon prescribes steroids, and the patient is advised to wear sunglasses.
- Corneal scarring which can result from a dense haze and interfere with vision. If it occurs in the periphery, it may not affect vision, but if it occurs in the center, the patient will need rigid gas permeable contact lenses or a scleral lens. If it's too dense as to obscure vision, the surgeon will opt for a corneal transplant.
Side effects and complications associated with corneal cross-linking may include:
- Blurred vision
- Stromal scarring
- Infectious keratitis
- Reduced visual acuity
- Corneal opacity (clouding)
- Increased photophobia (sensitivity to light)
- Ulcerative keratitis (severe eye inflammation)
- Herpetic simplex keratitis (viral infection of the eye)
- Corneal striae (when white lines occur on the visual field)
- Hot and painful eyes which also feel dry, burning, and gritty
After Care, Recovery & Results
After the procedure, antibiotic drops are prescribed to be used three to four times a day. The surgeon also prescribes pain medications in case the pain and discomfort become severe. Contact lenses should not be worn as the eyes need oxygen to heal. The patient should not rub the eyes for at least five days after cross-linking. Sun protection is recommended because squinting affects the healing eyes.
Eyeglass prescriptions may keep changing daily or even hourly until complete healing has taken place. In the first three months, the patient will record different visual acuities. From three months onward, the patient’s vision stabilizes even though there may be fluctuations. During this time, the eye’s curvature may undergo alterations. A new eyeglass prescription can be acquired when the eyes have healed, and vision has stabilized.