Discussion
The surgical indication was given in all four ulcers of this
retrospective study because of the depth of the corneal defect (4/4),
signs of melting (2/4), big diameter of the ulcus (4/4) and poor healing
conditions because of BOS (4/4).
Most commonly isolated bacteria in infected corneal ulcers are
Staphylococcus and Streptococcus spp. In this study Streptococcus canis
could be detected in two cases. In contrast, the corneal swab sample of
the melting ulcer in case 4 was negative.
While waiting for the antibiotic test results all ulcers in this study
were treated with systemic antibiotics and topical application of
preservative free antibiotic eyedrops before and after surgery.
Ulcerative keratitis has a vast range of causes in dogs. Brachycephalic
breeds have the highest prevalence of corneal ulcers with a twenty times
higher likelihood to be affected than non-brachycephalic dogs. The
predisposing factors include macroblepharon, shallow orbits with
subsequent lagophthalmos, medial canthal entropion, trichiasis, tear
film deficits and reduced corneal sensitivity. These factors are
collectively known as brachycephalic ocular syndrome (BOS). In one study
most of the mean values of ocular surface diagnostic tests were lower in
brachycephalic compared to non-brachycephalic dogs.
This study consisted of cases in which a therapeutic compromise had to
be found. Therapeutic management was limited due to financial restraints
(cases 2 and 4), compliance of the owners (cases 1 and 2) and
anaesthetic restraints due to the severe respiratory brachycephalic
syndrome (all cases). Surgical therapy was imperative in all four cases
because of the deep of the ulcers. The compromise was to use a xenogenic
biomaterial as scaffold and for replacing missing tissue without
suturing in combination with a third eyelid flap for providing bandage
and mechanical stability. These biomaterials have been used successfully
for surgical therapy of corneal defects in dogs and cats and replace
missing tissue und and serve for regeneration. They were applied either
alone or in combination with covering by a conjunctival flap , with
temporary lateral tarsorrhaphy and a temporary nictitating membrane flap
. All these grafts were placed in the defect and sutured in the
peripheral intact cornea tissue. This takes time and is an expensive
surgery. In some instances a short procedure time is imperative and/or
financial restrictions exist. Furthermore, suturing the cornea requires
microsurgical equipment and experience of the surgeon. Sometimes one or
both of these requirements are not met.
The main disadvantage of the third eyelid flap is to monitor progress or
worsening.
However the third eyelid flap is superior to a temporary lateral
tarsorrhaphy for full coverage of the nonfixated piece of SIS. In
addition, in case of worsening pain and increasingly discharge would be
expected and couldn’t be seen in all four cases.
Further limitations of the study were the small sample size and the
short follow up time in two cases. Studies with more patients and a
comparison group for further research into this technique should be
performed in future. But the first results presented in this case report
are promising that the modified surgical technique may be useful in very
selected cases because it makes the procedure easier and faster. In all
cases of this study the cosmetic and visual outcome was very good to
excellent.