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    Investigations of a novel retinal disease in Wiltshire sheep : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies in Veterinary Pathology at Massey University, Palmerston North, New Zealand
    (Massey University, 2014) Hunt, Hayley
    In 2011 and 2012, nine cases of adult-onset blindness were identified in a single flock of Wiltshire sheep. Affected sheep typically developed detectable night blindness at 2 to 3 years of age, which progressed to complete blindness by 4 to 5 years of age. Opthalmoscopically, the disease was characterised by progressive tapetal hyperreflectivity and attenuation of retinal blood vessels, indicative of retinal thinning and atrophy. Retinal histology revealed a selective loss of rod photoreceptors in the early stages of the disease, with preservation of cone photoreceptors. Secondary loss of cone photoreceptors was seen later in the course of the disease. Retinal degeneration was not accompanied by any other ocular or central nervous system abnormalities. Progressive retinal degeneration targeting rod photoreceptors has not been previously reported in sheep, but this disease has several similarities to inherited retinal dystrophies in other species, particularly progressive retinal atrophy in dogs and retinitis pigmentosa in humans. The disease in sheep is thought to be inherited in either an autosomal dominant or autosomal recessive manner, although additional cases identified recently provide further support for an autosomal dominant mode of inheritance. Initial investigations into the molecular basis of the disease, using a comparative candidate gene approach, did not identify any exonic single nucleotide polymorphisms (SNPs) in the rhodopsin gene of affected sheep that would alter the amino acid sequence. Homozygosity mapping of affected sheep revealed an identical-by-descent region on chromosome 5, but none of the genes within or surrounding this segment were considered to be plausible candidate genes except for GPR98, which is associated with retinitis pigmentosa and sensorineural hearing loss in humans. Investigations into the inheritance and molecular basis of this novel retinal degeneration in Wiltshire sheep are continuing, as this disease may prove to be a useful model for retinal dystrophies in other species, including retinitis pigmentosa in humans.
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    The applications of sub-Tenon's anaesthesia for canine ophthalmic surgery : a thesis presented in fulfilment of the requirements for the degree of Master of Veterinary Science (MVSc) at Massey University, Manawatu, New Zealand
    (Massey University, 2016) Bayley, Kellam David
    Sub-Tenon's anaesthesia is an indispensable anaesthetic technique in human ophthalmic surgery. It produces highly effective regional anaesthesia and has a significantly lower complication rate than the previously used peribulbar and retrobulbar injections. Although this technique has potential application to veterinary ophthalmology it has not yet been reported in clinical cases. This thesis reviews the literature that references local anaesthesia for ocular surgery in human and veterinary ophthalmology. A sub-Tenon's block technique that was specifically developed for use in dogs is also described. This technique is assessed with a prospective controlled clinical study testing this technique across a variety of ocular surgeries including enucleation, intrascleral prosthesis, keratectomy with a third eyelid flap and cataract surgery. The effect of sub-Tenon's anaesthesia on specific parameters was recorded and compared to the controls such as; globe position and rotation, pupillary dilation, general anaesthetic monitoring parameters, intraocular pressure, vitreal expansion and post-operative pain scores. Analysis of these parameters has indicated that sub-Tenon's anaesthesia was an effective option for controlling post-operative pain when used in conjunction with systemic analgesics and was an excellent alternative to systemic neuromuscular blockade for canine cataract surgery.