Page 7 - Clinical Connections - Summer 2022

 

 

 

 

 

Page 7 - Clinical Connections - Summer 2022
P. 7

Ophthalmology
        CORNEAL CROSS-LINKING PROGRESS

        Maria-Christine Fischer, Lecturer in Ophthalmology, and Vim Kumaratunga, Resident


              orneal cross-linking (CXL) is a highly   is paramount to drive the development of   The CXL machine was purchased with
              attractive treatment for infectious   non-traditional treatment options which   the aid of an  Animal Care Trust grant.
        C keratitis and melting (malacia). The   reduce selection pressure promoting   The registered charity of the  aims to
        ’s Ophthalmology Service has been   antibiotic resistance in bacteria.   improve animal health and care through
        offering it for more than two years.                                    clinical practice, education, and pioneering
          Infectious keratitis can have disastrous,                             veterinary research.
        sight-threatening consequences. The
        bacterial pathogens and the white blood                                 Growl Tiger
        cells recruited to defend the cornea                                    The three-year-old Shetland gelding ‘Growl
        both release various proteases. These                                   Tiger’ was treated with CXL recently
        can rapidly break down the collagen                                     with an excellent outcome. Growl Tiger
        matrix of the corneal stroma, leading                                   presented with a one-week history of
        to keratomalacia. This is often termed                                  deteriorating left corneal ulceration, which
        ‘melting’, due to the appearance of the                                 progressed to a keratomalacia. In his
        softened cornea. Infectious keratomalacia                               case, the malacia was severe and there
        poses a high risk of corneal perforation and                            was associated intraocular inflammation
        can lead to the loss of the eye.                                        (uveitis). This can be very painful and lead
          The first-line treatment for ulcerative                               to further intraocular complications, such
        keratitis currently involves highly intense                             as chronic distortion of the pupil, chronic
        use of topical antibiotics, ideally based                               intraocular scarring (synechiae) and can, in
        on cytology and culture and sensitivity                                 some severe cases, lead to glaucoma.
        results, as treatment success relies on the                              Treatment with CXL and placement of a
        pathogens being sensitive to the product                                sub-palpebral lavage system for ‘remote’
        chosen. However, bacteria that cause                                    delivery of eye drops, resulted in complete
        infectious keratitis are increasingly found   Growl Tiger undergoing corneal collagen   healing of the malacic corneal ulcer over
                                             cross-linking treatment of his left eye under
        to have multidrug-resistant profiles in   standing sedation. A special ultra-violet light   a period of three weeks. As a result of this
        veterinary medicine. Furthermore, the ever-  is used to activate riboflavin which has been   treatment, the team was able to save Growl
        increasing population of brachycephalic   applied to the left cornea    Tiger’s eye and vision and restore ocular
        dogs are at elevated risk of developing                                 comfort. Since discharge, Growl Tiger has
        ulcerative keratitis.                 CXL is well-established in human   returned to living a content life with good
                                            ophthalmology as is easy to perform, safe   vision and a comfortable eye.
                                            for the patient and can be combined with
                                            other surgical or medical therapies. This
                                            makes it a very appealing therapy for the
                                            treatment of corneal malacia.           Case Recruitment for CXL Research
                                              In addition to small animal patients,
                                            the Ophthalmology Service treats equine   The  Ophthalmology team is currently
                                                                               researching the antibacterial effect of cross-
                                            patients and species referred to the exotics  linking on corneas and conjunctiva of canine
                                            team. The CXL machine at the  is very  patients with infectious ulcerative keratitis
                                            easily portable, which makes it extremely   and is recruiting cases.
                                            useful for standing equine procedures   The inclusion criteria are infectious
         Growl Tiger’s left eye at initial presentation,
         prior to corneal collagen cross-linking   under sedation.             keratomalacia, bacteria present on cytology,
         treatment. There is a large, relatively deep,                         ulcer diameter of less than or equal to 12mm,
         malacic (“melting”) corneal ulcer present                             ulcer depth of less than or equal to 50%
                                                                               corneal depth and client consent.
          CXL increases resistance of corneal
        tissue to enzymatic digestion through                                  To refer or discuss cases, please contact Dr
                                                                               Maria-Christine Fischer or Dr Juliette Preston
        formation of new chemical bonds between                                via qmhophthalmologyteam@rvc.ac.uk.
        stromal fibres. In addition, CXL has the                                             .                                                       .
        ability to kill microorganisms regardless of
        their antimicrobial resistance pattern. Early
        treatment can halt progression of corneal
        melting and prevent surgical intervention
        and thereby improve visual outcome.   Growl Tiger’s left eye, three weeks after
          With the increasing prevalence in   corneal collagen cross-linking treatment. The     For small animal referrals, please call:
        infectious keratitis and the continued   region of ulceration had nearly completely   01707 666399
                                             healed. The melting cornea had been
        expansion of antimicrobial resistance, it   replaced with organised fibrosis (scar tissue)     Email:
                                                                                     qmhreception@rvc.ac.uk

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