Page 7 - Clinical Connections - Summer 2022

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 RVC Animal Care Trust grant.
C keratitis and melting (malacia). The reduce selection pressure promoting The registered charity of the RVC aims to
RVC’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 RVC 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 RVC 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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