ophthalmology Flashcards
(19 cards)
What is normal schemer tear test values, IOP in dog and cat
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
Why should hydrocortisone not be used locally in uveitis
Doesn’t penetrate the cornea. Use prednislon acetate 1% (if no ulcer)
Give one breed predisposed to primary glaucoma
Cocker spaniel, basset hounds, beagles, chow chow, shar-pei
Give three common causes of secondary glaucoma
Anterior uveitis, lens luxation, intraocular neoplasia
What is the mechanism of action of latanoprost in glaucoma tx
Prostaglandin (prostacyclin keeps the drainage cyclin). Increases drainage by causing intense miosis leaving more space for drainage
When in glaucoma tx is latanoprost contraindicated
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
What is the mechanism of action of methazolamide and dozolamide in glaucoma
Carbonic anhydrase inhibitors. Reduced production of aqueous
Give two local medications for glaucoma
Latanoprost, methazolamide (carbonic anhydrase inhibitors)
What inciting issue should the eye be examined for in a terrier with glaucoma
Often secondary glaucoma due to lens luxation
In corneal laceration, 3 important points to consider
Partial or full thickness. Aqueous leak or not. Lens involvement.
Give 2 signs the lens is damaged in full thickness corneal lacerations
Fibrin clot in anterior lens, focal cataract, iris laceration, (melanotic tissue in anterior chamber – suspicious)
State 2 prognostic factors for globe poptosis
Skull formation, pupil reactivity, severity of trauma to the globe and periocular structures
Shortly describe how to reposition a globe proptosis
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
What ophthalmological condition can sulfa treatment cause
Keratoconjunctivitis sicca
Why do we need life saving eye lube in the icu
Decreased tear production in canine icu patients. Average STT 24,5 mm/min versus 13.2 mm/min in non icu px
Describe an enucleation after skin preparation
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.
Describe a tarsorrhaphy
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.
What is the sympathetic pathway and classification in horners syndrome
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)
most common reasons for sudden blindness
Sudden acquired retinal degeneration syndrome, ivemectin dogs/enrofloxacin cats, cats after mouth gag, systemic hypertension, (potassium bromide intoxication)
