Principles of Ophthalmic Surgery Flashcards
give 10 differences of ophthalmic surgical instruments compared to those for general surgery
Weight –they are designed to be light – e e.g. titanium, or by
the presence of holes within their handles
The majority are designed to be held in a pencil grip and are thus of a similar diameter to a pen or pencil
Tactile feedback – ridges, knurling of the handles or flattening of them. Can also help to prevent slippage and can indicate the correct finger placement for holding and use.
Instruments can have a slightly dulled or dark finish to reduce the scatter of reflected light under the
microscope.
Ophthalmic instruments are often sprung so that the hand or wrist position does not need to be altered to
reopen the instrument.
A pin-stop may be present to prevent excessive pressure on closure leading to damage to the delicate tips.
Instruments which only operate in one direction – corneal scissors for example – often have flat handles
while those which require rotation during use, such has needle holders, may have rounded handles
A lock might be present – e.g. on needle holders - to allow grasping of the delicate needle without continued
digital pressure.
General ophthalmic instruments are 120 – 140mm in length while microsurgical instruments are shorter –
usually 100mm (so that they do not touch the bottom of the microscope during the procedure).
It is the surgical tips which need to be small – not the whole instrument – since it still needs to fit comfortably
in the surgeon’s hand!
what type of needle is used for corneal suturing?
spatula
what strength of povidine-iodine solution should be used to flush the conjunctiva sac and what is the required contact time?
1:50
3 mins
what cranial nerves are affected by a retrobulbar block?
III, IV, V, VI
what signs indicate an efficacious retrobulbar injection?
in pupil dilation, central rotation of the globe, inhibition of ocular
movement but no change to intraocular pressure
give 6 possible complications of retrobulbar injection
globe perforation haemorrhage intravenous injection damage to the optic nerve extraocular muscle myopathy intrathecal injection with possible resultant seizures or cardiorespiratory arrest
what are the 4 key factors to consider when performing ophthalmic surgery?
- Adequate restraint
- Correct surgical instruments
- Suitable magnification
- Appropriate delicate surgical technique.
a. Techniques to incise (separate tissue)
b. Tissue stabilisation (grasping)
c. Tissue re-alignment (suturing)
how deep should a corneal suture be?
2/3 corneal thickness
give 4 consequences of inappropriate/inadequate pain management
activation of stress response impairs wound healing
recovery from GA poor
post-op complication risk is higher
increased risk of self trauma
true or false: the deeper layers of the cornea have a higher density of nociceptors
false
give 6 clinical procedures or physiological factors that may directly or indirectly influence IOP
Venous pressure Arterial pressure Direct pressure on the globe Arterial blood gas tensions (PaCO2 and PaO2) Drugs Surgery
how long does anaesthesia reduce tear production in dogs for?
24 hours
For the surgical preparation of a site for a superficial keratectomy which of the following agents would be recommended?
a. A 1:50 dilution of chlorhexidine (without alcohol) and sterile saline to flush
b. Povidone iodine solution diluted to 1:10 for the skin and 1:50 for the conjunctival sac plus flushing with sterile water
c. A 1:10 dilution of chlorhexidine (without alcohol) for the skin, a 1:50 dilution of povidone iodine solution for the conjunctival sac and sterile saline to flush
d. Povidone iodine solution diluted to 1:10 for the skin and 1:50 for the conjunctival sac plus flushing with sterile saline
d. Povidone iodine solution diluted to 1:10 for the skin and 1:50 for the conjunctival sac plus flushing with sterile salinea
Define tarsorrhaphy.
A surgical procedure to partially close the eyelid margins
The depth of placement for corneal sutures is critical to achieve a successful surgical outcome. With a full thickness corneal wound how deep should the sutures be placed?
2 / 3 stromal depth
Sharp incisions are a frequently employed method of surgical cutting. They are most accurate in what tissue type?
a. Firm tissue with fibres which are cut rather than displaced by an incision
b. Loosely arranged tissue such as the cornea
c. Firm tissue with fibres which are easily displaced by a cutting action
d. Loosely arranged tissue such as the conjunctiva
a. Firm tissue with fibres which are cut rather than displaced by an incision
You are presented with a 5 year old terrier cross with an acutely painful right eye following a walk in the woods. On ophthalmic examination you note a corneal foreign body. The pupil is miotic but no dyscoria is present, nor can any hyphaema be appreciated. From this limited information, what is your assessment of the depth of this foreign body?
a. It is likely to be very superficial and easy to remove under topical anaesthesia alone
b. It is likely to be penetrating the anterior stroma
c. It is impossible to tell the depth of the material without anaesthetising the patient and examining under an operating microscope
d. It is likely to be perforating the cornea
b. It is likely to be penetrating the anterior stroma
What magnification of surgical loupes would be most appropriate for performing replacement of a prolapsed nictitans gland in a 14 week old bulldog puppy?
4.0 x magnification
Which of the following choices would be the most appropriate forceps to grasp the conjunctiva in a patient which is conscious, but has had topical anaesthesia applied to the conjunctival sac, in order for you to take a snip biopsy of the conjunctiva?
a. Colibri forceps
b. Von Graefe forceps
c. St Martins tying forceps
d. Bennet’s cilia forceps
b. Von Graefe forceps
The choice of suture and needle is very important in all ophthalmic surgery. Which of the following would be most suitable to repair a corneal wound when using 4.0 x magnification operating loupes?
a. 6-0 polyglactin on a spatula tipped needle
b. 8-0 polyglactin on a spatula tipped needle
c. 10-0 nylon on a spatula tipped needle
d. 8-0 polyglactin on a taper point needle
b. 8-0 polyglactin on a spatula tipped needle
