PVM: Ophthalmology

Retractor Muscle

(CN 6-abducens)

Oblique muscles

- Dorsal Oblique (CN 4- trochlear)-rotates the dorsal globe medially and ventrally - Ventral Oblique (CN 3-oculomotor)- rotates the ventral globe medially and dorsally

Carnivores

- binocular vision (front facing eyes) - open boney orbit - eye open later in life

Rectus Muscles

- dorsal, ventral, medial (CN 3- oculomotor) - lateral (CN 6-abducens)

Herbivores

- monocular vision (lateral facing eyes) - closed boney orbit - eyes open at birth

OU

both eyes

OS

left eye

Strabismus

misalignment of the eyes (one or both in any direction) -can be breed related (ie. Cross eyed Siamese)

Proptosis

protrusion of the globe outside of it's bony orbit (most often trauma related)

Nystagmus

rapid movement of the eyes (side to side, up and down, or in a circle) neurological problem vs genetic (again, Siamese)

Enophthalmos

recession of the globe deeper into the orbit due to loss of sympathetic tone, loss of periorbital fat, pain, or mass effect.

Ophthalmic history

• Changes in vision (dark vs bright light vs dim light, not seeing) • Discharge (color, amount, location; one or both eyes, consistency) • Redness (related to underlying disease process, allergic, infectious) • Behavior changes (won't go down hallway/navigate house differently, won't go out at night, sleep changes) • Location (one vs both eyes, only part of eye?) • Duration (how long?) • Progression of condition (gotten worse?) • Any changes in behavior/activity? • Pawing or rubbing eye? (think pain) • Any squinting and/or tearing? • Any known incident or trauma? • Indoor/outdoor, exposure to other animals? • If any other animals in house, are they showing signs too? New pets? • Diet?

Assessment of Vision

• Observe patient walking around room (can they see, do they bump into walls/furniture). • Cotton ball test: throw a cotton ball and does patient follow it (do in both bright and dim light)?

OD

Right eye

Exophthalmos

anterior displacement of the globe from the normal orbital position (retrobulbar mass, abscess, hemorrhage, cellulitis, etc

Buphthalmos

enlargement of the globe due to glaucoma (increased intraocular pressure)

Microphthalmia

globe too small (often congenital or secondary to trauma)