Ординатура / Офтальмология / Английские материалы / Notes on Veterinary Ophthalmology_Crispin_2005
.pdf
OF OCULAR |
SURGERY |
BASIC PRINCIPLES |
AND ADNEXAL |
348 |
Notes on Veterinary Ophthalmology |
•In addition, the peripheral pulse and systolic blood pressure can be monitored with a Doppler flow probe and cuff and end tidal carbon dioxide can be measured by a capnograph (carbon dioxide monitor).
Anaesthetic protocol
•Pre-anaesthetic agents – may be used singly or in combination, usually a sedative (e.g. acepromazine) and analgesic (e.g. buprenorphine)
•Pre-oxygenation can be used to avoid hypoxaemia at induction, but it is important to avoid pressure on the globe from the facemask
•Induction agents – intravenous induction is preferable to minimise excitement: thiopentone is applicable to most species, propofol provides smooth induction in dogs and can also be used for maintenance
•Endotracheal intubation is usually necessary when procedures involve gaseous agents for maintenance and laryngeal reflexes can be deadened by pre-treatment with topical or intravenous lignocaine or intravenous fentanyl
•It is important to avoid stimulating the larynx when performing intubation and extubation
•Maintenance is usually achieved with a gaseous anaesthetic agent and isoflurane is an excellent choice
•Whilst neuromuscular blocking agents are useful (e.g. to immobilise the globe prior to corneal surgery and for intraocular microsurgery), their use requires that the requisite skills and equipment are available
•The use of regional and local blocks for specific procedures is outlined in the relevant parts of the main text
•All intraocular procedures require a soft eye (the intraocular pressure is slightly lower than normal), whereas adnexal and ocular surface surgery is often easier if the eye is firm (the intraocular pressure is normal). Some of the factors that modify intraocular pressure are summarised in Appendix Table 3.1 below.
Appendix Table 3.1 Factors affecting intraocular pressure
Intraocular pressure is increased by: Intraocular pressure is decreased by:
Increased venous pressure (e.g. jugular Most anaesthetic agents occlusion from neck collar, choke chain,
poor positioning, anything that causes airway obstruction, coughing, gagging, retching, vomiting)
Systemic hypertension
Hypercapnia
Hypoxaemia
Drugs (suxamethonium; ketamine)
External pressure (e.g. direct pressure on the globe)
Decreased central venous pressure or arterial pressure
Hypocapnia
Drugs (osmotic diuretics, carbonic anhydrase inhibitors)
Oculocentesis (release of aqueous or vitreous)
Basic Principles of Ocular and Adnexal Surgery |
349 |
GENERAL EQUIPMENT
INSTRUMENTS
General instruments
•Surgical drapes and towel clips (NB adhesive drapes excellent for ophthalmic surgery)
•No.3 Swann Morton scalpel handle with numbers 15 and 11 blades
•Standard 1 ¥ 2 teeth tissue forceps (e.g. Gillies)
•Stout, straight scissors (e.g. Mayo)
•Needle holders (e.g. Crile Wood)
•Mosquito artery forceps ¥4 (e.g. Halstead)
•Tissue forceps ¥4 (e.g. Allis)
•Swabs
Ophthalmic instruments
•Small 1 ¥ 2 teeth tissue forceps (e.g. Lister)
•Fixation forceps ¥2 (e.g. Graefe)
•Small needle holder (e.g. Castroviejo)
•Small, straight, blunt-tipped tenotomy scissors (e.g. Stevens)
•WeissCEL microspears or similar
Suture material
•For skin sutures: 4-0 to 6-0 non-absorbable braided silk, or absorbable polyglactin 910 with curved, swaged-on, spatula, micropoint needle
•For conjunctival sutures: 6-0 to 7-0 absorbable polyglactin 910 with curved, swagedon, round-bodied or tapercut needle
•For corneal sutures: 8-0 to 9-0 absorbable polyglactin 910 with curved, swaged-on, spatula, micropoint needle or 9-0 to 10-0 nylon, with curved, swaged-on spatula, micropoint needle
OTHER EQUIPMENT
•Operating specatacles, or binocular loupe, or operating microscope (latter is essential for microsurgical techniques)
•Catholysis equipment
•Cryosurgical equipment
•Bipolar wet field cautery
INSTRUMENT SETS
Eyelids and conjunctiva
• General and ophthalmic packs of instruments
OF OCULAR |
SURGERY |
BASIC PRINCIPLES |
AND ADNEXAL |
OF OCULAR |
SURGERY |
BASIC PRINCIPLES |
AND ADNEXAL |
350 |
Notes on Veterinary Ophthalmology |
•Standard ophthalmic needleholder (e.g. Castroviejo)
•Speculum (e.g. Barraquer or Clarke)
•Entropion spatula (e.g. Jaeger)
Points to note
•For eyelids: precise apposition of skin edges with little tension on the knot is important. In general, single-layer closure with simple interrupted sutures is satisfactory for most eyelid problems. The eyelid margin is closed first and apposition should be perfect. The aim is always for primary repair.
•Buried absorbable sutures should be avoided in general, but may be required for conjunctival closure (including eyelid closure with complex blepharoplastic procedures, because more tension is needed for effective closure).
Distichiasis
•Catholysis equipment
•Cilia forceps (e.g. Whifield)
Ectopic cilia
•General pack of instruments
•Tarsal cyst forceps or chalazion clamp (e.g. Desmarre) – eyelid immobilisation is easier and haemorrhage is reduced
Lacrimal apparatus
•Ophthalmic pack of instruments
•Lacrimal cannulae, silver, non-disposable
•5ml or 10ml syringe
•Balanced salt solution or distilled water for irrigation
•Lacrimal probe set
•Monofilament nylon, polyethylene tubing to catheterise the duct
Superficial keratectomy
•General and ophthalmic packs of instruments
•Speculum (e.g. Barraquer or Clarke)
•Beaver handle and blades or disposable knife with miniature edged blades
Enucleation
•General pack of instruments
•Additional artery forceps
•Stout, curved scissors (e.g. Mayo) for dissection
•Curved forceps (e.g. Wright’s orbital forceps) for clamping optic nerve
Parotid-duct transposition
•General and ophthalmic packs of instruments
•Monofilament nylon (heat-blunt end to avoid trauma) to cannulate the parotid duct
•Strabismus hook (e.g. Graefe) useful for elevating the duct during dissection
Basic intraocular set
• Ophthalmic instrument tray
Basic Principles of Ocular and Adnexal Surgery |
351 |
•Fixation forceps ¥2 (e.g. Graefe)
•Wells artery forceps ¥2
•Halstead’s mosquito artery forceps ¥2
•Balanced salt solution for intraocular use
•Viscoelastic material for intraocular use
•Range of cannulae and syringes
•Swabs
•WeissCEL® microspears or similar
•Adhesive drapes and standard drapes with towel clips
•Speculum (e.g. Barraquer or Clarke)
•Callipers
•Mayo scissors (straight)
•Standard 1 ¥ 2 teeth tissue forceps (e.g. Gillies)
•Diamond knife or disposable knife, or razor blade and handle, or Beaver blades and handle
•Small 1 ¥ 2 teeth tissue forceps (e.g. Lister)
•St Martin forceps
•Birks forceps
•Colibri forceps (e.g. Barraquer)
•Capsule forceps (e.g. Arruga)
•Capsulorhexis forceps (e.g. Utrata)
•Small, straight, blunt-tipped tenotomy scissors, straight and curved (e.g. Stevens)
•Left and right corneoscleral scissors (e.g. Castroviejo)
•Castroviejo corneal scissors
•Westcott tenotomy scissors
•Iris scissors
•Vannas scissors
•Iris repositor (e.g. Nettleship)
•Needle holders (e.g. Crile Wood)
•Standard needleholder (e.g. Castroviejo)
•Micro needleholder without catch (e.g. Castroviejo, Barraquer)
•Strabismus hooks (Graefe) ¥2
•Vectis (Bell Taylor)
OF OCULAR |
SURGERY |
BASIC PRINCIPLES |
AND ADNEXAL |
APPENDIX 4
CRANIAL NERVE
INNERVATION OF
THE EYE AND ADNEXA
NERVE INNERVATION |
EYE AND ADNEXA |
CRANIAL |
OF THE |
Ner ve |
Function |
Damage |
|
|
|
Optic |
Vision |
Partial or complete blindness |
Cranial nerve II |
|
Dilated or completely unresponsive pupil |
special somatic afferent (SSA) |
|
|
Oculomotor |
GSE: Eyeball movement – supplies dorsal, ventral and |
GSE: Squint (lateral and inferior – ‘down and out’) |
Cranial nerve III |
medial recti and ventral oblique muscles; raises |
|
general somatic efferent (GSE) |
upper eyelid – levator palpebrae superioris muscle |
|
general visceral efferent (GVE) |
GVE: Pupil constriction and dynamic accommodation of the |
GVE: Dilated pupil (mydriasis) |
|
lens (parasympathetic) |
|
Trochlear |
Eyeball movement – supplies dorsal oblique muscle |
Squint (dorsal – upwards) |
Cranial nerve IV (GSE) |
|
|
Trigeminal |
Sensory to globe and adnexa |
Neurotrophic keratopathy (because of a loss of |
Cranial nerve V (GSE) |
|
corneal sensitivity) |
Abducens |
Eyeball movement and retraction – supplies lateral rectus |
Squint (medial – inwards) |
Cranial nerve VI (GSE) |
and retractor bulbi muscles |
Inability to retract globe |
Facial |
SVE: Muscles of facial expression |
Inability to close lids – exposure keratopathy |
Cranial nerve VII |
|
|
somatic visceral efferent (SVE) |
GVE: Lacrimal gland secretion (parasympathetic) |
Corneal desiccation |
and GVE |
|
|
Vagus |
Oculocardiac and oculorespiratory reflex (Vth nerve |
Not applicable |
Cranial nerve X (GVE) |
– afferent, to internuncial fibres in reticular formation, to |
|
|
vagus nerve – efferent) |
|
|
Stimulation produces a decrease in respiratory rate and |
|
|
variation of its rhythm, and slowing of heart in some species |
|
|
if there is manipulation of the globe +/- adnexa (e.g. the |
|
|
extraocular muscles) |
|
Sympathetic Nerves (GVE) |
Pupil dilation; supplies smooth muscle and blood |
Horner’s syndrome (typically ptosis, miosis, |
|
vessels within orbit and eyelids |
enophthalmos, prominence of third eyelid) |
|
|
|
Adnexa and Eye the of Innervation Nerve Cranial
355
CRANIAL NERVE INNERVATION OF THE EYE AND ADNEXA
FURTHER READING
(Useful texts first published in English)
FURTHER READING