Corneal cross-linking: Halting keratoconus progression

Corneal cross-linking is a proven treatment that strengthens the cornea to halt the progression of keratoconus, preventing further visual deterioration. Miss Zahra Ashena, consultant ophthalmic surgeon in London and Essex, tells us more. 

What exactly is keratoconus and why does it require treatment?

Keratoconus is a progressive eye condition where the normally round cornea thins and bulges into a cone shape. This distortion causes significant blurring and sensitivity to light, often starting in late adolescence or early adulthood. Without intervention, the weakening cornea can continue to degrade, leading to severe vision loss that may eventually require a transplant. In the UK, approximately one in 2,000 people are affected, though prevalence rates vary by region and screening intensity.

The condition is distinct from standard refractive errors like myopia because it involves structural failure of the corneal tissue rather than just optical focus issues. Early detection is vital as the disease often stabilises naturally in later life but can be aggressive in younger patients. If left unchecked, the thinning can lead to acute swelling known as hydrops, which causes sudden pain and scarring.

How does cross-linking stop the disease from getting worse?

Corneal cross-linking works by using ultraviolet A (UVA) light combined with riboflavin (vitamin B2) drops to create new bonds between collagen fibres in the cornea. This process stiffens the cornea, effectively acting as an internal brace that prevents further bulging. The treatment doesn’t reverse existing curvature but successfully halts progression in over 95 per cent of cases according to long-term studies.

Riboflavin acts as a photosensitiser that reacts when exposed to specific wavelengths of light. This reaction generates free radicals that form covalent bonds within the corneal stroma. The resulting increase in biomechanical stiffness makes the cornea more resistant to the intraocular pressure that drives the ectasia forward. Clinical data suggests the procedure reduces the risk of needing a corneal transplant by up to 80 per cent compared to untreated eyes.

What should patients expect during and after the procedure?

The procedure typically takes about 30 minutes and is performed under local anaesthetic drops to ensure comfort. During the session, the doctor removes the outer layer of the cornea to allow the riboflavin to penetrate effectively before exposing the eye to UVA light. Patients remain awake throughout and may feel mild pressure but no sharp pain due to the numbing agents used.

Recovery involves a period of healing where the epithelium regrows over three to five days. Vision may fluctuate during this time, and patients must use antibiotic and anti-inflammatory eye drops for several weeks. Most individuals return to normal activities within a week, though contact lens wear usually needs to be suspended for a longer duration.

• Avoid rubbing your eyes vigorously as this can strain the healing tissue.
• Wear dark sunglasses outdoors to reduce glare sensitivity while the cornea heals.
• Use prescribed eye drops exactly as scheduled to prevent infection and inflammation.

How is this treatment made available?

Access to corneal cross-linking in the UK has expanded significantly, though availability varies by region and clinical need. The National Institute for Health and Care Excellence (NICE) recommends the procedure for patients with documented progression of keratoconus.

Private practice offers faster access for those who wish to avoid waiting times. It ensures immediate consultation and tailored follow-up schedules without regional funding constraints. However, the underlying medical indication remains the same regardless of whether the pathway is public or private.

Patients should discuss their specific progression rate with their consultant to determine if they meet the criteria for intervention immediately. Early action is the most effective strategy to preserve long-term vision quality and avoid more invasive surgical options later in life.

References

• National Institute for Health and Care Excellence (NICE). Interventional procedures guidance [IPG734]: Corneal collagen cross-linking for keratoconus. NICE, 2022.
• Raiskup F, et al. Corneal Collagen Cross-Linking with Riboflavin and Ultraviolet-A Light for Progressive Keratoconus: Long-term Results. Journal of Cataract & Refractive Surgery, 2018.
• The Royal College of Ophthalmologists. Keratoconus Guidelines. RCOphth, 2021.
• Wollensak G, et al. Crosslinking of human corneal collagen: the role of pH and oxygen. Cornea, 2003.