Clinical Connections  –  Spring 2020

The RVC’s Ophthalmology Service now offers corneal cross-linking (CXL), which is a cost-effective alternative to surgical treatment and can allow the cornea to heal more naturally and without major scarring.

CXL is well-established in human ophthalmology and is easy to perform, safe for the patient and can be combined with other surgical or medical therapies. This makes it a highly attractive therapy for the treatment of corneal malacia.

It can improve quality of life for the patients by shortening duration of hospitalisation, lowering stress levels associated with reduced frequency of application of eye drops and improved visual outcome.

Corneal malacia represents a serious, vision-threatening condition and is typically caused by secondary bacterial or fungal corneal infections. The microorganisms together with resident inflammatory cells lead to collagenolysis, rapidly progressing ulceration and even perforation of the cornea. The RVC Ophthalmology Service sees around 80 patients with infected and melting corneal ulcers annually.

CXL increases the resistance of corneal tissue to enzymatic digestion by through the formation of new chemical bonds between stromal fibres. In addition, the UV light kills microorganisms, which supports treatment of cases with resistant microorganisms and potentially helps to decrease the use of antibiotics. Early treatment may halt the progression of corneal melting, prevent surgical treatment and thereby improve the visual outcome for patients.

Prior to the treatment becoming available, the protocol was aggressive treatment with topical antimicrobials and anticollagenases to stop the melting process. However, the results of medical treatment are variable. This is related to several factors including antimicrobial drug resistance of pathogens, inability of owners to adequately follow drug therapy and problems with patient compliance. In a significant number of cases, corneal melting necessitates tectonic surgery, which often results in extensive scar tissue formation and visual impairment. Some advanced cases require enucleation and some owners elect euthanasia over treatment.

By providing this innovative treatment we hope to improve visual outcome in our patients, on the one hand by stabilising the melting process early in the disease course and thereby reducing the scar tissue formation, and on the other hand by avoiding extensive keratoplasties or/and by improving corneal graft survival. Clients could benefit from reduced costs and duration of treatment and may, therefore, be more likely to decide against enucleation, or euthanasia in extreme cases.

The RVC has the capacity to offer CXL treatment thanks to funding from the Animal Care Trust. As well as to our referral patients, the development has benefits for clinical research and undergraduate and postgraduate teaching.

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