Module 11 & 12

Question 1

Equipment

Answer 1

Magnification: 2-4x for lids. minimum 5x for corneal, conjunctival, IO (sometimes up to 25x). Loupes: 2-7X, operating microscope (full range of magnification)

Loupes: binocular, varying depths, illumination from theatre light or head mounted. Direction of view can be easily changed. Mostly for working around eye, parotid duct transposition, enucleation etc. Fixed magnification and wobbles with higher magnification.

Operating microscope: corneal and intra-ocular sx can be carried out to greater degree of accuracy. Floor or ceiling mounted. Foot control for focus, zoom and movement of field of vision. Cost and fixed position during sx meaning cannot view from different angles, instruments introduced blind. Practice and competence.

Illumination: IO surgery requires co-axial illumination. Tapetal reflex helps highlight IO structures.

Question 2

Equipment

Answer 2

Positioning: lateral, dorsal or ventral recumbency. Important to get this right at beginning sx. Sit on stool at suitable height to allow maximum control over instruments. Vacuum supports and sand bags are helpful here.

Instruments: personal preference, delicate tips do not need to have small handles, rounded handles can be useful for rotating during use. Titanium instruments cause less glare. Must be well looked after to maximise life span.

• keep in sterilising box
• use tip covers for delicate tipped instruments
• Ensure blood rinse off before drying out
• open spring- handle instruments for cleaning
• instruments should be wiped on cellulose sponges, avoid gauze swabs
• use ultrasonic cleaner, do not scrub and rinse in instrument lubricant
• dry after autoclaving
• divide into groups for 1) lids and conjunctival and 2) corneal and IO procedures

Question 3

Equipment

Answer 3

Suture: small-gauge monofilament non-absorbable should be used as they cause less tissue reaction as in the case in human ophtho, but as vets we would prefer absorbable and not so concerned about inflammation.

Polyglactin mostly used - vicryl or vicryl rapide.
Polydioxanone (PDS) longer lasting but difficult to handle.
Nylon and silk can also be used.

Needles: needles are larger than the material they are attached to. Needle to diameter ratio 5:1. Knot can be buried within the tract if required.

Larger degrees of arc for small but deep bites, smaller degrees of arc for large shallow bites.
Taper - least traumatic - conjunctiva
spatula-tipped - corneal sx
Cutting or reverse cutting - skin

Suture patterns: vectors:

• perpendicular to the wound - compresses
• parallel to the wound - cause the tissue to shift relative to each other
• perpendicular to the tissue - exert inverting or everting forceps

Question 4

Equipment

Answer 4

Patient preparation: minimal clipping to avoid irritation after. UGA. ointment (KY jelly) placed into conjunctival sac while clipping with scissors or small clippers. IO sx canthotomy site clipped. eyelashes trimmed with scissors. Careful hair clipping removal.

Sx prep: 1) apply ky jelly to eye, clip with ky clippers so hair sticks to them

2) 1:50 (0.2%) dilution povidone iodine soln, rptly flush conjunctival sac
3) sterile saline, use 5-10ml to flush conjunctival sac
4) 1:10 (1%) povidone iodine, clean skin with gauze free swabs

Povidone iodine is light sensitive, keep the dark!

SOLUTION not SCRUB!!

Ideally make up on the day but can be used for up to one week.

Question 5

Proptosis of the globe

Answer 5

Usually secondary to head trauma, relatively less force needed to proptose globe in brachys. Thus must be assessed for head trauma.
Reposition UGA ASAP and keep moist until then.
Lateral canthotomy and gentle pressure to reposition.
Haemorrhage and swelling mean the globe does not usually resume normal position and temporary tarsorrhaphy +/- TEL flap.
2/0 to 4/0 non-absorbable horizontal mattress sutures +/- stents
ABs 7 days and NSAIDs
Px vision is poor, globe salvage is aim of sx.
Favourable px indicators: brachy dog, PLR direct and consensual, normal findings on posterior exam, vision prior to replacement.
Unfavourable: non-brachy or cat, hyphaema, no pupil, facial #, ON damage, avulsion of 3+ EO muscles.
Medial rectus is first to rupture, retain a lateral strabimus.

Question 6

Removal of the eye - enucleation, exenteration, evisceration

Answer 6

Enucleation: removal of the globe - transpalpebral or transconjunctival. The latter is quicker but has increased risks of leaving conj and forming fistulas, should be avoid if there is any surface infection or neoplasia. Not necessary to ligate the external ophthalmic artery, pack with a swab and remove just before wound closure.
Blindness of fellow eye may be encountered, especially in cats, if too much traction is put on the optic chiasm. Great care should be taken not to pull at the globe.

Evisceration and intrascleral silicone sphere implant: cosmetic salvage procedure.

• Pthitic, microphthalmos, septic endophthalmitis, neoplasia - not candidates
• Primary glaucoma is most common indication and even works well is very hydrophthalmic eyes
• Sphere chosen according to diameter of opposite cornea or breed average
• 8mm long limbus based conj flap prepared, 3mm incision into sclera 4mm behind this.
• Cyclodialysis spatula introduced between uvea and sclera and rotated to loosen uveal tract
• Scleral wound enlarged according to size of implant and uvea removed, sometime lens removed separately (with a vectis)
• contents sent for pathology
• scleral shell irrigated, care not to touch endothelium as this will cause corneal decompensation and implant extrusion.
• prosthesis implanted manually or with introducer. Wounds closed with 6/0 vicryl
• Abs and NSAIDs 14 days.
• corneal vascularisation, may occur over 2-4 weeks post op, will subside but become pigmented.
• complications in 10% cases but would be less if pt selection carried out correctly

Question 7

Third eyelid surgery

Answer 7

TEL flaps: Two methods: 1) free margin of TEL sutured to lateral aspect of upper lid,
2) free margin of TEL sutured superotemporal episcleral tissue
Option 2 is better as moves with globe

Scrolled cartilage: young giant breeds mostly, is seen in cat also. Eversion>inversion.
Sx to excise bent portion of vertical arm carried out from posterior aspect of TEL. Pull up with two pairs of artery forceps or stay sutures. Incision perpendicular to free edge of TEL, overlying bent cartilage. Care to only incise bulbar conj. Bent cartilage is bluntly dissected and excised. Consider pocket at same time to prevent prolapse if any sign of hypertrophy.

Prolapsed nictitas gland (cherry eye): seen in many breeds - Bull dog, grt Dane, Lhasa Apso etc., due to weak connective tissue. Pink mass appears in medial canthus and with chronic exposure becomes enlarged and inflamed leading to ocular discharge and irritation. Excision is not acceptable –> KCS. Anterior or posterior anchoring techniques and pocketing/imbricating methods.

The Morgan’s pocket: 2x incisions, one above and one below the gland. Slightly arched but should not meet! 3mm margin between free edge of TEL and limbus is required to close the pocket. Dissection is required to allow the gland to bury. Pocket closed in 6/0-8/0 vicryl in simp cont with knots buried or placed on the other side of the TEL. Swelling for 2-3 weeks. Avoid topical steroid post op.

Trauma to TEL: fights, FBs, sx intervention. always attempt to retain/reconstruct a functional membrane and margin

Question 8

Eyelid Sx

Answer 8

Aims: keep pt free from life threatening dz, maintain optimum comfort and eyelid function, retain vision, effect cosmetic appearance.

Abnormalities which may require sx:

• congenital defects - coloboma
• breed related abnormalities - entropion, ectropion, diamond eye, lagophthalmos - medial canthal syndrome in brachys
• eyelid trauma - fresh injuries or those which have resulted in cictricial damage and resultant deformity
• eyelid neoplasia

Suture material: 5/0 or 6/0 vicryl or vicryl rapide. P needle.
Some permanent SC suture may be required (3/0 prolene) for canthal repositioning and tie down.
Where conjunctiva needs suturing this is usually with 8/0 vicryl.

Question 9

eyelid - Simple eyelid defect/wedge resection

Answer 9

Some lesions and ectropion - “wedge resection”.
two parallel incisions perpendicular to lid margin, on either side of the lesion.
Full thickness and leave clear margin in case of neoplasia. Two smaller incisions “roof” the house shaped incision.
Suture must not contact cornea and eyelid margin must be completely accurately apposed
Figure of eight (cruciate) pattern should be used
Rest of the wound closed in one or two layers

Question 10

eyelid - entropion

Answer 10

In-turning part or entire eyelid:

• Spastic - from ocular pain due to eyelid muscle spasm, corrects with LA
• anatomical - breed related and likely to have a hereditary basis, present 4-12 months old
• cicatricial - due to scarring
• atonic - lack of muscle tone, e.g. elderly ECS

Lateral entropion seen in animals with appropriate lid length e.g. Retriever, Rottweiler etc.
Diamond eye - mixture of ectopion and entropion in the same eye.
Anatomical entropion is care in cats except persians with medial entropion

Pre-op assessment important. Examine after LA to eliminate spastic component.
If spastic component may need to consider lens placement and tacking temporarily while source of pain resolves.

Question 11

eyelid - entropion

Answer 11

Hotz celsus: simple lateral lower entropion usually corrected with hotz-celsus +/- extension around canthal region. If lateral canthus in-turning may benefit from sub-conjunctival sectioning of the lateral palpebral ligament.

Stades: atonic entropion may require combination of rhytidectomy and upper lid sx. Resection of an ellipse of skin in midline of the head or back of the head and immobilising the skin by suturing connective tissue around the uncial crest. Atonic trichiasis correct with stades, similar to a Hotz celsus but the two incisions are not sutures together and initial incision is closer to lid margin. 20mm on hair bearing skin is removed, and sutured to subconjunctiva, leaving a 5mm section to heal by secondary intention. This leaves and area of hairless scar tissue.

Y to V plasty: for correction of cicatricial entropion

Question 12

Ectropion

Answer 12

Outward turning of the eye, can be:

• anatomical
• cicatricial
• atonic in senile dogs (ECS)
• due to paralysis
• iatrogenic (over-correction of entropion)

Does not always require surgery, mostly needs correction when it is combined with entropion.

Diamond eye - bloodhound, st Bernard, Great Dane, clumber spaniel, english mastiff, Neapolitan mastiff etc. where the problem is exacerbated by excessive facial and neck skin

Macroblepharon - shortening procedure is required e.g. Khunt-szymanowski technique

Some patients lack lateral canthal support and may benefit from repositioning lateral canthus to tension the lids, by: orbicularis oculi muscle dissected out and stretched laterally and suturing it to connective tissue (Wymans lateral canthoplasty), or by suturing the canthal tissue to the connective tissues adjacent to the zygomatic arch using non-absorbable material. Some degree of lateral canthal repositioning is achieved with the modified khunt-zymanowski also.

V to Y: best for cicatricial ectropion.

Question 13

Macropalpebral fissure and lagophthalmos

Answer 13

Brachy dogs and cats have large palpebral fissure. Results in poor blink, reduced corneal sensation, hairy caruncle, nasal fold trichiasis. . Corneal damage and poor tear film distribution. Corneal pigmentation centrally from medial limbal region.
Tx: medial or lateral canthoplasty. Medial beneficial as removes the in turnign lid margin and the caruncle at the same time. Double layer closure, tension releasing sutures around the primary repair most simple.
Must be over-corrected in first instance as skin stretches at operated site over several months.

Question 14

Surgery involving replacement of lid margin

Answer 14

defect 1/3 or less can be dealt with by simple apposition, figure-of-8 at lid margin.

Eyelid trauma: simple - minimal debridement and primary repair. Large - may need to be dealt with medically initially, secondary repair appropriate to the size and location. Lower canaliculus involvement should be cannulated for 6 weeks in order to maintain patency

Neoplasia: dogs - benign mostly 80%, cats - malignant mostly. if <1/3 a simple wedge will be used. Histo where possible, always with cats. Larger may require more extensive plastic sx procedures (Mustarde or lip to lid) or cryo. Chemo for cutaneous lymphoma.

A number of techniques in literature, all bring hairy skin up and suturing to conj, hairs are often misdirected onto cornea causing irritation and possibly ulceration. Contracture of this area during healing results in notched area and exposure keratopathy.

Question 15

Surgery involving replacement of lid margin

Answer 15

Mustarde procedure (cross lid flap): transfer of normal lid tissue into the defect from the opposite lid and defect is shared between lids. e.g. if defect in one lid is 2/3 then 1/3 of other lids can be moved into defect and both lids shortened by 1/3 each. Two stage procedure but advantages far outweigh this.

Lip to lid procedure: when more than 2/3 in lower lid, a new lid margin formed from muco-cutaneous junction can be created by transfer of the lip attached to pedicle of skin to the lower lid region. Must be twisted 180 degrees to achieve this, can end up with crumpled area of skin, which can be correct weeks later if desired.

Theoretically for large upper lid defects it is possible to fill this with lower lid using the mustarde technique and then fill the lower lid defect with a lip to lid

Question 16

Corneal sx

Answer 16

Reasons: ulceration, trauma, FB, opacification, neoplasia

Magnification is essential. lateral canthotomy can facilitate exposure. Nerumuscular blockage during GA assists positioning, essential for IO sx. Otherwise careful stay sutures or forceps may be acceptable. Aims - correct defects and provide support for healing

Corneal surgery: tarsorrhaphy, keratotomy, direct corneal suturing, cynoacrylate adhesive, non-ocular graft material, conj flaps and grafts, corneoconjunctival and scleral transpositions, penetrating and lamellar keratoplasties, FB removal

Suture: 8/0 to 10/0.

Placement: needle enter perpendicular, penetrate 2/3 thickness, pass through wound at same depth and emerge perpendicular to the cornea. Once tied, the suture should result in accurate apposition, watertight seal and checked with cellulose sponge.
Knots - double overhand throw, followed by 2 or 3 single throws in alternative direction. Nylon - triple overhand then 3 single throws. Cut short and rotate into suture track.
Pattern - simple interrupted, mattress, cruciate or continuous. Mattress - high tension areas. Continuous at limbal incisions and clean lacerations - simple or saw tooth - starting and finishing at same end.

Question 17

Corneal sx

Answer 17

Cyanoacrylate adhesives: glue used in small corneal defects. small partial laceration, pin-point descematocoeles and small diameter deep stromal ulcers. Not infected ulcers or perfs.
Ophthalmic Hexabond - N-butyl cyanoacrylate. N-butyl removes exothermic reaction. Polymerises on contact with fluid. cornea must be dried with canned air and then glue applied layer by layer using 30g needle and allowed to dry in between layers. should not emerge beyond the level of corneal surface. 5 minutes polymerisation time should be allowed at the end.

Non-ocular grafts: 
porcine submucosal collagen (VetACell) - corneal defects
Aminotic membrane (omnigen) - resurface cornea, on its own or with other products

Question 18

Conjunctival flaps and grafts

Answer 18

Provide support for the weakened cornea without risk of host rejection. Bulbar or palpebral conj mucosa with epithelium and connective tissue.

Flaps made my undermining a sector of the bulbar conj and suturing it to the cornea to cover the ulcer. Speculum and lateral canthotomy are useful to increase exposure.

Incision in conj 1-2mm from the limbus and extend 90-120 degrees around the eye and free from underlying tissue by blunt dissection. Can then pull down over defect (advancement flap) or by making second incision parallel to the first and transecting one end of the flap and rotating into place (rotational/pedicle flap).

Suture into place with simple interrupted. Ulcer bed can be debrided if necessary to remove devitalised tissue.

Question 19

Corneo-conjunctival transposition

Answer 19

Transplants adjacent cornea and bulbar conjunctiva into the wound/keratectomy site. Should be delayed in infectious keratitis until infection cleared

Corneal bed prepared to remove disease tissue, by keratectomy. For the graft two slightly diverging corneal incisions at the appropriate depth to remove the lesion are made and extended to the limbus. Lamellar dissector used to separated the anterior stroma and epithelium from deeper stroma up the limbus. Limbus is traversed and conj mobilised with small tenotomy scissors. Conj graft should be wider than recipient site to allow for graft shrinkage.
Graft can be sutured into place using simple continuous or interrupted pattern.
Temporary tarsorrhaphy useful in the immediate post op period to tamponade the graft bed.
Limbal region transposed onto the axial cornea will always be apparent but central visual axis will remain clear and vision not impaired

Question 20

Lamellar and penetrating keratoplasties

Answer 20

becoming more common in our patients but not common place even in referral

Corneal transplantations

Question 21

Trauma

Answer 21

Oblique superficial laceration usually heal without repair. Tidying the wound ULA with scissors may enhance healing. Deeper injuries benefit from reconstruction. Gentle flushing with saline to remove foreign debris. Povidone iodine avoided.

If peroration it may be filled with coagulated aqueous, can be removed with surgical sponge or iris repository. If iris involved and fresh it should be repositioned into anterior chamber. If contaminated it should be excised. Anterior chamber can be reformed with BSS or air.

Corneal lacerations: partial or full thickness, full thickness divided into those without or without iris prolapse, with or without lens involvement, with or without loss of ocular contents.

1) wound must be sealed without incarceration of uveal tissue
2) anterior chamber must be re-established

Animals <1 more likely to develop glaucoma or phthisis bulbi

Px impacted by: cause of injury, iris prolapse >24 hours, axial or central lacerations, additional ocular involvement (lens, haemorrhage, scleral laceration etc.) - all reduce prognosis for vision

Enucleation or evisceration if large corneal laceration, loss of IO contents and no prospect for vision

Small cat scratches may seal spontaneously and only require a few simple interrupted sutures.

Uveal prolapse - gentle reduction required, far better to have small anterior synechia than to risk IO haemorrhage at time of sx so better to replace if poss. Need to be supported by conjunctival flap

Question 22

Foreign bodies

Answer 22

Superficial - remove with surgical spear or FB spud
Deeper - necessary to incise overlying cornea to gain access to the foreign material. Forceps not recommended as inadvertently push FB further into the eye, use one or two needles to stab object and pull out in line of entry in reverse

intra-corneal FBs: those embedded in stroma (penetrating) and those partially in the cornea and protruding into the anterior chamber (perforating), the latter may be approached from outside or inside, if outside it can be useful to place a horizontal mattress across the defect before removal.

Penetrating - no fibrin in anterior chamber or the cornea
perforating - fibrin in the anterior chamber or on the cornea, pupil often misshapen (dyscoria). Fluorescein can be applied to determine presence of aqueous leakage.

Atropine is key post op!

Penetrating - few complications
perforating - scarring, anterior uveitis, especially if anterior lens capsule damage which is undetected or unmanaged will go onto to develop phaecoclastic uveitis and prognosis is poor.

Question 23

Opacification

Answer 23

corneal sequestrum, symblepharon, dermoid - superficial keratectomy may be required

defect can be left to heal but if deep may require conjunctival flap or corneo-conjunctival transposition

Question 24

Superficial keratectomy

Answer 24

Cornea and anterior stroma excised to remove diseased tissue. If it extends beyond 1/2 to 2/3 depth then a graft or transposition must follow.

When the entire cornea is affected a limited depth corneal trephine may be used, or by dividing into four quadrants and cutting like a pie. Beaver no. 64 is a good instrument for this, purpose made lamellar knives are available.

Desired depth estimated with slit lamp beforehand. The dissection plane in stroma should remain same depth, can be achieved by holding blade tangential to the corneal stroma to prevent progressively deeper dissection. Lamellar knife avoids this as it relies on blunt dissection. Any remaining tags then cut away with scissors.

Contact lens post sx to relieve discomfort and allow monitoring of healing process.

Question 25

Medical support follow corneal ulceration, injury and sx

Answer 25

Reflex uveitis: atropine, cyclopentolate, tropicamide
Infection: topical and systemic antibiosis
Pain: analgesics
Contact lenses
Inflammation/post healing: NSAIDs, cyclosporine, tacrolimus, (steroids?)

Drops if IO involvement, NOT ointments

Question 26

Aqueocentesis and intracameral injections

Answer 26

Aqueocentesis: small gauge needle (23-26g), paracentesis will cause BAB breakdown, UGA + LA, surgical prep of globe, stabilised with rat-toothed forceps. Hypodermic needles directed through the peripheral cornea or limbus into anterior chamber. Contact with iris and lens avoided. 0.1-0.3ml aspirated. Needle tract will self seal. Post op - topical Abs, NSAIDs, and mydriatics (unless glaucoma)

Question 27

Sx for anterior lens luxation (intracapsular extraction)

Answer 27

Lendectomy - operating microscope.
lateral canthotomy.
170 degree corneal incision. Cornea is grooved with scalpel blade (Beaver 65), entered with No11 scalpel blade and completed with corneal scissors.
Cornea held open and lens extracted with a vectis/lens loops or a cryo-extractor
Minimal vitreal loss, but may be liquefied, vitrectomy with cellulose sponges or corneal scissors
Cornea closed with 8/0 vicryl in a continuous pattern and anterior chamber re-inflated with BSS or air

Question 28

Cataract extraction

Answer 28

Phacoemulsification:
pre-op assessment:
*PLR - good response good but does not prove vision, nor does neg response mean retinal dz
*dazzle reflex - pos suggests good pathway, neg not of concern
*STT - KCS delays healing and will impact post op care
*fluorescein - establish corneal dz pre op
*IOP - uveitis or glaucoma
*gonioscopy - at risk breeds
*Electroretinography (ERG) - if any doubt about retinal function
*ocular US - assess for retinal detachment, vitreal dz, hyaloid vessels, lens capsule rupture

Dx tests:

• haematology and biochemistry - check for underlying dz
• urine analysis - renal insfficiency and DM
• BP
• work up any concurrent dz
• DM patients need stability - fructosamine and glucose curves.

Topicals:

• Atropine, tropicamide, phenylephrine - dilate pupil
• Topical steroid - AIs
• Topical NSAID - AIs - stabilise BAB
• ABs - chloramphenicol - reduce infection