Enucleation
Synonym(s): eye: surgical removal
Introduction
- The enucleation procedure involves the surgical removal of the globe.
- It involves the transection of the six extraocular muscles and the optic nerve (minimal amounts of extraocular muscle and periorbital tissues are removed).
- The most common approach used in bovines is the transpalpebral technique.
- An exenteration procedure involves the surgical removal of the globe and all periocular tissue down to the level of the bone. Again the most common approach used in bovines is the transpalpebral technique.
- Note: the exenteration technique is more commonly used for cases of severe diffuse ocular and perioccular squamous cell carcinomas (SCC).
Uses
- Indications for enucleation/ exenteration include the following:
- Extensive inflammation (panophthalmitis) or trauma to the orbit or periorbital tissues (abscessation).
- Severe exophthalomos resulting in exposure keratitis.
- Severe perforating ulceration.
- Glaucoma.
- Extensive ocular and periocular neoplasms- commonly SCC, lyphosarcomas.
- Severe Infectious bovine keratoconjunctivitis (IBK) Infectious bovine keratoconjunctivitis that has resulted in globe rupture.
- Congenital defects.
Advantages
- Relatively straight-forward technique to carry out.
- Successful surgery results in the animal remaining in the herd.
Disadvantages
- Severe pyogenic infection or diffuse neoplasia can make the procedure more technically difficult.
- Entire diseased tissue may not be removed, ie neoplasm.
- Orbital infection may cause wound breakdown (and rejection of prosthesis, in the unlikely event of a prosthesis being used in cattle!).
- Transpalpebral technique is associated with an increased risk of hemorrhage.
- Severe swelling post-surgery is often observed.
- Note: ensure a discussion about the short-term aesthetics (gross swelling of the orbital cavity) and long-term aesthetics (chronic appearance of a concavity of ocular recess), of the procedure, is had with the client.
Technical problems
- Despite adequate head restraint, moderate to heavy sedation and local anethestic, it is likely the animal will react during the course of the surgery.
- The animal may react to auditory (other cows, machinery etc), physical (palpation of non-anesthetised regions of the head and neck) and olfactory (aseptic preparations and blood) stimuli.
- Excessive tension on the globe, during procedure, may damage the optic chiasm and disturb vision in the opposite eye.
- Ruminants have 20% shared vision, from opposite eye, via the optic chiasm.
- Poor surgical technique may result in excessive hemorrhage.
- Excessive removal of skin may make wound closure difficult.
Alternative techniques
- Tranconjunctival enucleation.
- Evisceration – removal of the contents of the globe only.
- Commonly carried out when using a silicon cosmetic prosthesis in other species.
Time required
Preparation
- 10-15 min.
Procedure
- 30-45 min.
Decision taking
Risk assessment
- Oculocardiac reflex (vasovagal response) via vagus nerve (CN X) during anesthesia may cause reflex slowing of heart and possibly ventricular fibrillation.
Requirements
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Preparation
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Technique
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Aftercare
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResouce.
Other sources of information
- Anderson D E & Rings M (2008) Current Veterinary Therapy: Food Animal Practice. 5th edn. Elsevier Health Sciences.
- Divers T J & Peek S (2007) Rebhun's Diseases of Dairy Cattle. 2nd edn. Elsevier Health Sciences.
- Fubini S L & Ducharme N (2004) Farm Animal Surgery. 1st edn. Elsevier Health Sciences.