Keratoconus (KCS) & Corneal Collagen Cross-Linkage (CXL)

Keratoconus (KCS) is a degenerative, possibly inherited corneal disorder that usually affects both eyes. The incidence is approximately one person in every 2000 but it may affect up to one person in 450 in some populations. The disease process is incompletely understood but typically affects young adults and may be progressive. Surgical intervention including corneal transplantation may be required in up to a quarter of those affected.

What is Keratoconus?

The cornea is the transparent dome of collagenous tissue that forms the front protective surface of the eye. KCS causes the cornea to thin progressively, a process called ectasia. Ectasia results in the cornea changing shape becoming irregular which causes blurring of vision. This blurring is often accompanied by increased light scatter resulting in an increased sensitivity to lights e.g. car headlights that may become dazzling or appear with streaks or haloes around them. These symptoms are usually worse at night when our pupils naturally dilate making certain tasks such as night driving particularly difficult.

Opticians may detect KCS when they measure progressing short sightedness (myopia) and increasing astigmatism. Ophthalmologists can often detect changes in the cornea when they examine patients using a slit lamp biomicroscope with the most sensitive equipment such as elevation-based topography allowing the earliest detection and ability to monitor progression.


I tend to divide treatments into two groups; Refractive or Therapeutic.

Refractive treatments

These are treatments designed to improve vision but which do not alter the clinical course of the condition. The mainstay of refractive treatment is the use of contact lenses although spectacles may be worn initially. This often begins with the use of soft contact lenses and then progresses to the use of gas-permeable and other rigid lenses. Other refractive treatments include:

  • INTACS or Ferrara ring inserts – see NICE guidance
  • Refractive cataract surgery or refractive lens exchange
  • Intra-ocular contact lens (ICL)
  • Topography guided (T-CAT) excimer laser treatment – see NICE guidance

Therapeutic treatments

These are designed to replace the degenerative cornea by corneal transplantation (see Penetrating Keratoplasty and Deep Anterior Lamellar Keratoplasty Information), or treatment designed to stabilize disease progression. CXL is a treatment designed to stabilize and halt progression of KCS with the aim of preserving vision and avoiding the requirement for tissue transplantation if possible.

Corneal Collagen Cross Linkage (CXL) Treatment

Please read in conjunction with NICE Guidance IPG466

CXL using riboflavin (Vitamin B2) eye drops combined with ultraviolet A (UVA) light is the first interventional treatment that has been shown to stabilize KCS. It is a relatively new procedure but has been and is being thoroughly evaluated by clinical investigation including laboratory study, clinical trial and randomized prospective clinical trials.

Research is on-going and further randomized, controlled trials (RCT’s), which are considered to be the ‘gold-standard’ of medical evidence are expected to report soon. The procedure has been evaluated by the National Institute of Clinical Evidence (NICE) who have recently approved ‘epithelium-off’ CXL for the treatment of Keratoconus.

Corneal Collagen Cross-Linkage explained

David Anderson has been performing CXL since 2010 and uses the Avedro Accelerated KXL System CXL is performed as an outpatient procedure using local anaesthetic in the form of eyedrops. The procedure is painless and is completed within 30 minutes, with the outpatient visit lasting around an hour in total.

CXL has been shown to be highly effective in the treatment of KCS, stabilizing the condition to halt progression. All medical procedures carry risks as well as benefits but the risk of serious complication with CXL treatment is rare and estimated to be ~1%.

David has published on Accelerated CXL treatment (see Research) and has combined CXL with refractive treatments designed to improve the vision of affected patients.  These results were presented at the ESCRS conference in Milan in 2013.

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