Opthalmic Exam and Orbital Disease Flashcards
What are some things that are special about the equine eye compared to others?
Prominent globe - lateral, high
Horizonal elliptical pupil
Corpora nigra
350 degree visual field
What is the normal sequence of an Opthalmic exam?
- Examine from a distance - in good light - look for ability to move, symmetry, discharge
- Examine close up (dark room)
-Restrain
-CN
-Sedate and block
-Tear test, pressure
-Eye lid, conjunctiva, naso lacrimal duct
-Cornea and slcera
-Anterior Chamber - iris, pupil, lense
-Fundic exam - optic nerve, tapetum
What are some thing you could see from afar that may tip you off to an ocular disease?
Ocular discharge, asymmetry, normal eyelid position or downward
What cranial nerves should you assess before sedation?
Menace
Dazzle
Palpebral
PLR
What regional nerve blocks should be performed for an eye exam?
Auriculopalpebral (motor) and Supraorbital (sensory)
How do you block the auriculopalpebral and what are the landmarks?
Auriculopalpebral - motor - facial nerve and orbicularis oculi muscle
25G 1ml lidocaine lasts 1-2 hours
Caudal posterior ramu of the mandible, dorsal highest point zygomatic arch, on the zygomatic arch caudal to bony process of frontal bone
How do you block the supraorbital nerve and what are the landmarks?
Supraorbital - sensory - trigeminal
25G 1 ml lidocaine, last 1-2 hours
Thumb below dorsal orbital rim and middle finger in supraoribital fossa, index finger straight down, midway between the thumb and middle finger to locate supraorbital foramen
What is a normal value on a STT and IOP?
STT: >20mm/min
IOP 15-30mmHg (anastetic needed for tonopen)
What are some indications for irrigation of the Nasolacrimal Duct?
Epiphora, mucoid discharge and nasal puncta discharge
Sedation and retrograde common
How do you know if a horse has a cataract?
Direct focal illumination (darker) - dialate for completeness
Where is the optic disc located?
Non-tapetum part
What bones make up the orbit?
Frontal, lacrimal, zygomatic, temporal
Sphenoid and palatine
What nerve innervates most of the extraocular muscles?
Oculomotor nerve
What are some orbital disease and how do they present?
Sunken or buldging
Enopthalmos, micropthalmos and phthisis bulbi
What is enopthalmos?
recession of globe in orbit
-loss orbital contents
-fracture, loss fat, dehydration, sympathetic denervation
What is microthalmia?
Congenital anomaly resulting in small globe
-nonvisual
-shrunken
-enucleate if uncomfortable
What are some disease of the orbit that cause buldging?
Bupthalmos and Exopthalmos
What is bupthalmos?
Enlarged globe with chronically increased IOP second to glaucoma
-Corneal edema or haabs striae
-May or may not have vision
What is exopthalmos?
Anterior discplacmeent normal sized globe
-mass, cellulitis, trauma
-pain or nonpainful
What are some other orbital diseases?
Orbital fracture, fat prolaspse, cellulitis, neoplasia
What area of the eye is at the greatest risk of fracture?
Orbital rim and zygomatic arch
What can cause an orbital fracture?
rearing, kick, collide with object
What should you do if you think you have an orbital fracture?
Lubricate the cornea
Check visual status
Work on lacerations
think about if surgery is indicated
How do you diagnose orbital fat prolapse?
Fine Needle Aspirate or Biopsy
