Corneal crosslinking
Who can benefit from corneal crosslinking?
Corneal crosslinking is a vision-saving treatment that is used to prevent further deterioration of vision for people with keratoconus. The most common use of corneal crosslinking is for the treatment of keratoconus but it can also be used for the treatment of several other corneal conditions. In some cases there may be a modest improvement in vision following corneal crosslinking, however, glasses, contact lenses or other surgical procedures may be required to further improve vision once crosslinking has been used to stabilise the cornea.
Keratoconus is a disorder associated with changes in corneal shape resulting in poor vision due to shortsightedness and irregular astigmatism. Keratoconus is a progressive disorder that worsens over time and can cause significant visual impairment. In most cases, keratoconus is first diagnosed in the teenage years and may progress over several decades. The severity of keratoconus, age of onset, and rate of progression can vary from person to person. Although early keratoconus may cause only mild changes in vision, moderate to advanced forms may be associated with significant visual impairment that can be difficult to correct. The corneal shape changes typical of keratoconus, such as thinning and distortion, cannot be fully corrected with glasses or soft contact lenses.
Corneal crosslinking is the only treatment that has been proven to stop the progression of keratoconus. Corneal crosslinking can be used to treat several corneal disorders:
Keratoconus
Pellucid marginal degeneration
Ectasia following refractive (laser) surgery
Infective keratitis (this form of crosslinking is known as ‘PACK CXL’)
Other forms of corneal ectasia (warpage)
Without corneal crosslinking approximately 20% of people with keratoconus will develop severe vision loss and require a corneal transplant to restore functional vision.
What is corneal collagen crosslinking?
Corneal crosslinking is a surgical procedure designed to stabilise vision in people with keratoconus. The goal of corneal crosslinking is to halt the progression of keratoconus and prevent further loss of vision. Corneal crosslinking works by strengthening the cornea and halting the progression of keratoconus. After crosslinking, the strengthened cornea is more resistant to thinning and distortion and the vision should remain stable. In the majority of cases, a single treatment of corneal crosslinking will completely halt the progression of keratoconus and stabilise the corneal shape in that eye for the rest of your life.
Crosslinking involves the use of a vitamin B2 eye drop (riboflavin) combined with ultraviolet light treatment to strengthen the cornea. Riboflavin is a naturally occurring nutrient that can be found in many foods such as almonds, milk, rice, grains, and eggs. Due to its bright yellow colour, riboflavin is a common colouring agent used in energy drinks, ice cream, soups and other foods. The riboflavin used for corneal crosslinking is a medical-grade product that is formulated for use on the eye. Several different formulations of riboflavin are available to provide optimal treatment for a range of corneas.
The crosslinking procedure involves soaking the cornea in riboflavin and then exposing the soaked cornea to an ultraviolet (blue) light. The ultraviolet light appears blue in colour and is absorbed by the riboflavin. As the light is absorbed it triggers the production of ‘reactive oxygen species’, a type of molecule that induces strong bonds (‘cross links’) between the collagen fibres (structural elements) in the cornea. This process strengthens the cornea and prevents further loss of vision by halting the progression of keratoconus.
How is corneal crosslinking completed?
Corneal crosslinking typically takes approximately one hour to complete. There are several different crosslinking protocols that can be used. All corneal crosslinking protocols involve the use of riboflavin eye drops and ultraviolet light.
Anaesthetic eye drops are used to numb the cornea and keep you very comfortable during the crosslinking procedure. A cleaning solution is used to prepare the cornea and remove any bacteria from the skin around the eye. In some cases, the thin gel-like layer on the surface of the cornea will be gently wiped away. Riboflavin, a bright yellow liquid, is applied to the cornea until it has soaked through. Although the cornea is just 0.5mm thick, it takes 20-30 minutes for the riboflavin to penetrate deeply to enable effective crosslinking.
Once the riboflavin has soaked deeply into the cornea, ultraviolet light is used at a precise brightness to enable crosslinking to occur. The ultraviolet light is directed onto the riboflavin-soaked cornea for a precise amount of time. The ultraviolet light appears as a soft blue light that makes the riboflavin-soaked cornea glow a bright green colour during the procedure.
When the crosslinking is completed, antibiotic eye drops are used to prevent infection during the healing phase. It typically takes a few days for the cornea to heal. During that time the eye can feel irritated and scratchy and the vision can be blurry. It is important to keep your eye clean and dry and use the supplied eyedrops as directed. Plenty of rest can be helpful to promote healing and a rapid recovery. Most people will find that their vision and comfort will return to normal within two to three days after crosslinking but in some cases, it may take slightly longer.
What types of corneal crosslinking are available?
There are two main types of corneal crosslinking, epithelium-off (also known as standard crosslinking) and epithelium-on (also known as transepithelial crosslinking).
Epithelium-off crosslinking involves the removal of the outer protective layer of the cornea (epithelium) before the application of riboflavin and UV light. The epithelium is a natural barrier on the surface of the eye that reduces the penetration of riboflavin into the cornea. Epithelium-off is the original form of crosslinking and is considered as the gold standard. Removing the corneal epithelium enables riboflavin to penetrate freely into the cornea, but it also has a longer recovery time, causes more discomfort, and may have a higher risk of complications.
Epithelium-on crosslinking involves the use of a modified riboflavin that is designed to penetrate the epithelium without the need to remove it. Leaving the epithelium intact results in less discomfort after the surgery, faster recovery and may reduce the chance of infection or other complications.
Numerous studies have compared epithelium off and epithelium on crosslinking. Both forms appear to be effective for the treatment of keratoconus. Some studies have reported that removing the epithelium may be associated with greater improvements in corneal shape (flattening). Leaving the epithelium on may be associated with lower rates of infection and discomfort following crosslinking.
Many other variations of crosslinking have also been developed and may be useful if certain situations. Some protocols use higher-intensity UV light for shorter time periods, pulsed UV light, or personalised UV doses for the treatment of thinner corneas in advanced keratoconus.
What to expect on the day of your crosslinking
Cross-linking is a day-stay procedure which is performed under local anaesthesia (with numbing eye drops). The procedure is painless but your eye(s) can be sore for one or two days while they recover and your vision will be blurry over this time. You will be given some pain relief tablets and eye drops to use after the crosslinking.
The crosslinking procedure involves cleaning around the eyelid(s) to remove any bacteria that may be present on the skin or around the eyes. The cells on the surface of the cornea are gently removed to allow the riboflavin drops to soak into the cornea. It can take up to 30m for the riboflavin to fully soak into the cornea. The riboflavin-soaked cornea is then exposed to an ultraviolet (blue) light for approximately 10 minutes. After the crosslinking treatment is complete, antibiotic drops are applied to prevent infection. The entire process takes about 60 minutes per eye.
On the day of your crosslinking wear comfortable loose-fitting clothing and avoid any makeup. You may want to wash your hair and have a shower prior to your crosslinking as you will need to keep your eyes clean and dry after the procedure. You will need a driver to take you home as you will not be able to drive yourself after the crosslinking has been completed.
What to expect after crosslinking
After crosslinking it is important to keep your eye clean and dry and use eye drops as directed. Eye drops are typically required four times a day for one month. These eye drops prevent infection and help with healing after the procedure.
Initially, your eye(s) may feel irritated and uncomfortable while the surface heals over the first 2 - 3 days. You will be given a prescription for pain relief tablets to help keep you comfortable after your surgery. You will have blurry vision and will need to keep your eyes clean and dry following the crosslinking while your eyes recover. It is advisable to plan for at least 3-5 days off work/school. Avoid any appointments or events for 3 days after your procedure as you may feel your eye(s) are sore and your vision blurry during this time. A medical certificate for time off work/school can be provided if required.
If you are a driver, vision will be tested at your follow-up visit after your surgery before you will be legal to drive again. Sunglasses may be helpful following surgery as you will be sensitive to light. You will be given a shield to use to protect your eyes at night while sleeping.
You will have a follow-up appointment booked one week after your procedure for a post-operative check. You can also expect appointments at 1, 3, 6, and 12 months post-procedure to be sure the crosslinking has been successful.
Vision correction after crosslinking
Crosslinking is designed to stabilise the cornea and prevent further worsening of vision. Although crosslinking can in some cases be associated with a modest improvement in vision, many people will require some form of vision correction following surgery. Depending on the severity of keratoconus, glasses or contact lenses may be required to provide clear vision following crosslinking. There are several surgical options including intracorneal ring segments and implanted collamer lenses that may be suitable to provide a permanent correction of your vision following crosslinking.
Summary
Corneal crosslinking is a vision-preserving treatment for people with progressive keratoconus and other corneal disorders. The treatment is safe and effective with a high success rate. Please do not hesitate to get in touch if you have any questions or need an appointment for surgery.
You can book an appointment online or call on ☎ 0800 CATARACT (0800 228 27 228). If you need an appointment to discuss crosslinking surgery please get in touch and we will do our best to arrange an appointment within the next 1-2 weeks.
For any other questions please feel free to email info@jamesandeye.co.nz
