ophthalmology

Question 1

What is normal schemer tear test values, IOP in dog and cat

Answer 1

STT >15 mm/min dogs, >9 mm/min in cats
IOP 10-20 mmHg in eyes without anterior uveitis, <10 mmHg in eyes with anterior uveitis or significant lower than a contralateral eye without uveitis

Question 2

Why should hydrocortisone not be used locally in uveitis

Answer 2

Doesn’t penetrate the cornea. Use prednislon acetate 1% (if no ulcer)

Question 3

Give one breed predisposed to primary glaucoma

Answer 3

Cocker spaniel, basset hounds, beagles, chow chow, shar-pei

Question 4

Give three common causes of secondary glaucoma

Answer 4

Anterior uveitis, lens luxation, intraocular neoplasia

Question 5

What is the mechanism of action of latanoprost in glaucoma tx

Answer 5

Prostaglandin (prostacyclin keeps the drainage cyclin). Increases drainage by causing intense miosis leaving more space for drainage

Question 6

When in glaucoma tx is latanoprost contraindicated

Answer 6

Anterior lens luxation. Will cause miosis behind the luxated lens and further impair outflow of fluid. Careful in uveitis as will increase inflammation and the miosis will increase stickiness between iris and lens – less drainage of aqueous

Question 7

What is the mechanism of action of methazolamide and dozolamide in glaucoma

Answer 7

Carbonic anhydrase inhibitors. Reduced production of aqueous

Question 8

Give two local medications for glaucoma

Answer 8

Latanoprost, methazolamide (carbonic anhydrase inhibitors)

Question 9

What inciting issue should the eye be examined for in a terrier with glaucoma

Answer 9

Often secondary glaucoma due to lens luxation

Question 10

In corneal laceration, 3 important points to consider

Answer 10

Partial or full thickness. Aqueous leak or not. Lens involvement.

Question 11

Give 2 signs the lens is damaged in full thickness corneal lacerations

Answer 11

Fibrin clot in anterior lens, focal cataract, iris laceration, (melanotic tissue in anterior chamber – suspicious)

Question 12

State 2 prognostic factors for globe poptosis

Answer 12

Skull formation, pupil reactivity, severity of trauma to the globe and periocular structures

Question 13

Shortly describe how to reposition a globe proptosis

Answer 13

3 sutures at lid margin, scalpel handle beneath suture on lubricated cornea, replace eye lids. Tarsorrhaphy for approx. 3-4 weeks. Local antimicrobial, atropine, systemic broad spectrum antimicrobials, anti-inflammatory steroids

Question 14

What ophthalmological condition can sulfa treatment cause

Answer 14

Keratoconjunctivitis sicca

Question 15

Why do we need life saving eye lube in the icu

Answer 15

Decreased tear production in canine icu patients. Average STT 24,5 mm/min versus 13.2 mm/min in non icu px

Question 16

Describe an enucleation after skin preparation

Answer 16

Using a No. 15 scalpel blade, make elliptical full-thickness incisions about 5 mm away from the eyelid margins, and join the incisions at the medial and lateral canthu
Using Allis tissue forceps or towel clamps, grasp the incised eyelid margins. Start blunt dissection by using curved Metzenbaum scissors, alternating sides until you approach the sclera.
If the conjunctiva is accidently cut and the cornea is visible, you can close the hole created with Allis tissue forceps and proceed with the dissection. Avoid the angularis oculi vein at the dorsomedial aspect of the orbital rim. If hemorrhage occurs, ligate the vein immediately.
As the blunt dissection deepens into the orbit, it is difficult to release the globe until the medial and lateral canthal ligaments are transected. To locate the medial broad ligament, run your finger along the medial aspect of the orbital rim while placing upward tension on the lids by using Allis tissue forceps. Direct a perpendicular No. 15 blade halfway between the eyelid incision and orbital rim and cut downward with slow, controlled tension
Repeat the same procedure above for the lateral canthal ligament which is less broad and easier to transect
Identify the orbital rim
Using Metzenbaum scissors, create a plane of dissection to release the globe from the remaining tissues that are attaching it to the orbital rim.
Traction on the extraocular muscles stimulates a vagal reflex. Do not use excessive force, twisting, or traction because these actions can damage the optic chiasm. Clamping or ligating the optic nerve and surrounding blood vessels (short and long posterior ciliary arteries) before dissection is optional and often unnecessary. Sever the optic nerve and posterior ciliary arteries by using curved Metzebaum scissors.
Once the globe is removed, pack the orbit with gauze, and apply pressure for at least five minutes. If excessive bleeding is noted from a vessel, ligate the vessel. Minor capillary bleeding will achieve hemostasis once closure is started. Synthetic hemostasis products can be applied (Gelfoam-Pfizer, Surgicel-Ethicon) if you are unable to identify the source of bleeding.

Question 17

Describe a tarsorrhaphy

Answer 17

Temporary tarsorrhaphy: 2 or 3 partial-thickness horizontal mattress sutures are placed with nonabsorbable material (4-0 or 5-0 nylon or silk) and stents to bring the upper and lower lids together, leaving a small opening at the medial canthus to allow for postoperative application of topical medications. Stents (IV tubing, rubber band, or buttons) help prevent pressure necrosis of the skin by reducing tension from the suture material.
Care must be taken to ensure proper suture placement (i.e., needle through the meibomian gland openings, not the palpebral conjunctiva) and to close each suture tight enough to avoid any space between the upper and lower eyelids. A gap between the eyelids, whether noted intraoperatively or postoperatively when the periocular swelling subsides, should be addressed promptly to avoid corneal irritation or ulceration from suture material contacting the ocular surface.

Question 18

What is the sympathetic pathway and classification in horners syndrome

Answer 18

First, second (preganglionic) or third order (post ganglion)
From brainstem to T1-T4 segment (first) – cervical sympathetic trunk (vagosympathetic trunk) to cranial cervical ganglion (second) – through middle ear cavity to retrobulbar region (third)

Question 19

most common reasons for sudden blindness

Answer 19

Sudden acquired retinal degeneration syndrome, ivemectin dogs/enrofloxacin cats, cats after mouth gag, systemic hypertension, (potassium bromide intoxication)