Corneal Collagen Crosslinking (CXL) for Keratoconus

Patient Experience

  • Reference Number: HEY1023/2023
  • Departments: Ophthalmology Department
  • Last Updated: 29 September 2023


This leaflet has been produced to give you general information.  Most of your questions should be answered by this leaflet.  It is not intended to replace the discussion between you and your doctor, but may act as a starting point for discussion.   If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team who has been caring for you.

What is a corneal collagen crosslinking (CXL)?

Corneal collagen crosslinking (CXL) is a treatment to prevent your keratoconus getting worse. It successfully prevents worsening of your keratoconus in more than 90% of cases.

Keratoconus gets worse due to the shape of your cornea becoming more like a cone. Your eye doctor may use the term “progression of your keratoconus”. This happens due to your cornea being too flexible. CXL aims to make the cornea stiffer and prevent any further shape change. If the cornea is allowed to change shape, progressive sight loss can occur. In time, your glasses may stop giving you clear vision and you would need to wear rigid contact lenses. Without treatment, the shape of the cornea can continue to worsen meaning you would eventually need a corneal transplant. By performing CXL at the correct time, we hope to make corneal transplantation for keratoconus obsolete.

After gentle wiping away of the top layer of your cornea, vitamin B2 drops (Riboflavin) are dropped on to the cornea, normally for 20 minutes. A special UV light is then placed in front of your eye for 10 minutes. The combination of Riboflavin and UV light causes extra connections (cross links) to form between the collagen fibres that make up your cornea. This results in your cornea becoming stronger. This is a process that occurs naturally with age.

Why do I need corneal collagen crosslinking (CXL)?

CXL is recommended to patients whose keratoconus is getting worse or who are at a particularly high risk of progressive keratoconus. Your eye doctor will consider your spectacle prescription, your corneal topography (a special map taken of the front of your eye), your vision and also your age when making the decision to offer CXL. As natural cross-linking occurs with age, CXL would not be routinely offered to patients in their mid-thirties onwards.

Keratoconus (and a similar condition called pellucid marginal degeneration) are the most common indications for CXL. Less common reasons to offer the treatment include post laser eye surgery ectasia (keratoconus caused by laser eye surgery) or serious corneal infection.

The evidence behind CXL currently suggests that it is the only treatment proven to prevent keratoconus from getting worse. It prevents worsening of a keratoconus in more than 90% of cases.

As well as preventing your keratoconus from getting worse, CXL can improve the shape of your cornea. This happens in approximately 45% of cases. As a result, your vision with either spectacles or contact lenses after cross-linking, can be improved.

Can there be any complications or risks?

As with any surgical treatment, there are possible complications and risks that must be considered carefully. CXL is generally a safe procedure. Approximately 3% of patients (3 in 100 patients) lose some vision due to corneal scarring, corneal haze, corneal infection or an irregular corneal shape following CXL treatment. In the majority of these cases of visual loss, a corneal transplant can restore or improve your vision. If you are at a particularly high risk of developing a complication, this will be explained to you in clinic.

Approximately 20% of patients (1 in 5 patients) with progressive keratoconus would eventually need a corneal transplant if CXL is not performed. The risk of requiring a corneal transplant is most likely higher if CXL is not performed.

The complications and risks will be discussed with you at your clinic appointment. You will be asked to sign a consent form. The complications/risks listed on the consent form will include:

  • Infection of the cornea
  • Scarring of the cornea
  • Haze of the cornea
  • Delayed healing of the surface of your eye
  • Failure of CXL and the need for a further CXL treatment
  • Dry eyes
  • Causing an irregular corneal surface
  • Temporary or permanent loss of vision
  • Need for corneal transplantation

How do I prepare for corneal collagen crosslinking (CXL)?

Please read the information leaflet.  Share the information it contains with your partner and family (if you wish) so that they can be of help and support.  There may be information they need to know, especially if they are taking care of you following the treatment.

The vast majority of CXL treatments are done under local anaesthetic (ie. you will be awake). Please ensure you arrange for a friend or relative to drive you home after the procedure. Please bring a pair of sunglasses to wear after the treatment. They will help keep the eye more comfortable on the way home.

If, after discussion with your eye doctor you would prefer to have the procedure under general anaesthetic (ie. you are asleep) then you will be given instructions about when to have your last meal and drink leading up to the treatment. If you are put to sleep, we will often organize a bed for you on our ward and you may stay one night. You would need to bring an overnight bag.

What will happen?

Your treatment will take place in the Ophthalmic Theatres on the first floor of the Eye Hospital. You should report to the Ophthalmic Day Case Unit on the first floor at the time given on your patient letter. Our nursing staff will greet you. They will check your details, check your blood pressure and get you ready for surgery. There will be other patients waiting in the unit waiting for a variety of treatments.

Your procedure will be performed by an eye doctor (also called an eye surgeon or Ophthalmologist). It will either be a Consultant or one of their eye doctors in training in a “pilot/co-pilot” scenario. The doctor will see you before the surgery giving you the opportunity to ask any other questions you have. The doctor will use a surgical marking pen to draw an arrow over the eye we are planning to treat.

When theatres are ready for you, a member of the team will collect you and walk you to theatre. You will have local anaesthetic drops and some iodine drops put into the eye in the anaesthetic room. You will then be taken into theatre.

Overall the procedure takes approximately 35 minutes. At the end of the procedure, the eye doctor puts in a soft contact lens (also called a bandage contact lens) that stays in until you see the doctor in clinic. If it falls out before the clinic appointment, please throw it away. Do not try to put it back in.

The nursing staff on the day unit will run through some basic do and don’ts and discharge you with the necessary medications.

You are given four types of eye drops and a short course of painkiller tablets.

The eye drops are:

  • An antibiotic eg. Ofloxacin. This is an antibiotic to prevent infection. Use it four times a day for two weeks.
  • A steroid eg. Prednisolone 0.5% preservative free. This is a steroid to control eye inflammation. Use it four times a day for two weeks.
  • A lubricant eg. Celluvisc 1% preservative free. This is a lubricant and should help encourage healing. Use it four times a day for four weeks.
  • Local anaesthetic eg Proxymetacaine 0.5%. This will help control the pain following the procedure. You will be given three small bottles of Proxymetacaine. Use it as regularly as you need in the first 24 hours after surgery. We do not provide more than three bottles as this drug can slow down healing if too much is used.

You are also given 3 days worth of painkiller tablets. These are Co-codamol 30/500mg. These tablets contain Codeine AND Paracetamol. We will check you are not allergic to this medication or have no other medical reasons to avoid taking it.

What happens afterwards?

Once you have been discharged from the Ophthalmic Day Case Unit (or eye ward if you had a general anaesthetic) you should return straight home. After the local anaesthetic used by the eye doctors has worn off, the eye can become very painful. This is normal in the first 48 hours. The eye should become progressively less painful during the first 72 hours.

We advise you rest in a darkened environment with your eyes closed. It often helps to listen to music or an audiobook to distract you from the discomfort. By day three after the operation the eye should be less painful. Once the surface of your eye has grown back over, you should be pain free. This is normally by days 5 to 7. If your eye becomes painful again after previously being pain free, you must contact the eye service immediately and arrangements will be made for you to see an eye doctor the same day.

Use your eye drops as prescribed. An appointment will be made for you in the corneal clinic. This is normally two or three days post treatment. It is likely that your doctor at this appointment will remove your bandage contact lens.

It normally takes approximately 2 weeks for your vision to recover back to the level of vision you had before the treatment. After your initial post operative check up, a further appointment is made for you for three months later. This is to check the shape of your eye and your spectacle prescription.

Please contact the Eye Clinic if you need any further advice on telephone (01482) 816658 or 608788 (8.30 am – 5.00 pm, Monday-Friday) or Out-of-Hours (01482) 604346 (Please listen to full voice message on how to access emergency out of hours service).

This leaflet was produced by the Ophthalmology Department, Hull University Teaching Hospitals NHS Trust and will be reviewed in September 2026.

General Advice and Consent

Most of your questions should have been answered by this leaflet, but remember that this is only a starting point for discussion with the healthcare team.

Consent to treatment

Before any doctor, nurse or therapist examines or treats you, they must seek your consent or permission. In order to make a decision, you need to have information from health professionals about the treatment or investigation which is being offered to you. You should always ask them more questions if you do not understand or if you want more information.

The information you receive should be about your condition, the alternatives available to you, and whether it carries risks as well as the benefits. What is important is that your consent is genuine or valid. That means:

  • you must be able to give your consent
  • you must be given enough information to enable you to make a decision
  • you must be acting under your own free will and not under the strong influence of another person

Information about you

We collect and use your information to provide you with care and treatment. As part of your care, information about you will be shared between members of a healthcare team, some of whom you may not meet. Your information may also be used to help train staff, to check the quality of our care, to manage and plan the health service, and to help with research. Wherever possible we use anonymous data.

We may pass on relevant information to other health organisations that provide you with care. All information is treated as strictly confidential and is not given to anyone who does not need it. If you have any concerns please ask your doctor, or the person caring for you.

Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about you. For further information visit the following page: Confidential Information about You.

If you or your carer needs information about your health and wellbeing and about your care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.

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