Clinical Ophthalmic Anatomy

Question 1

describe the bony orbit (case)

Answer 1

1. comprised of 5-7 bones depending on species; complicated area with lots of important stuff, all of which can impact the eye (difficult to image bc lots of soft tissue superimposition)
2. frontal, sphenoid, palatine, zygomatic, lacrimal in everyone
   -variable: maxillary, ethmoid, temporal
   -DONT NEED TO KNOW BONES
3. open/incomplete in dogs and cats
   -closed/complete in horses, cattle, sheep, goats-NEED TO KNOW
4. base of the orbit is open for everyone! important stuff has to get there (good) but anything from mouth (infection, foreign body) can enter orbit too (bad)

Question 2

describe the extraocular muscles (5 total types)

Answer 2

rectus muscles: all innervated by CN III (except lateral, CN VI)
1. superior
2. inferior
3. lateral: CN VI
4. medial

oblique muscles:
1. superior: innervated by CN IV; intorsion; pulls 12 o’clock medially
2. inferior: innervated by CN III; extorsion; pulls 12 o’clock laterally

retractor bulbi: innervated by CN VI; retracts globe (bulb)

levator palpebrae superioris: innervated by CN III; elevated upper (superior) eyelid (palpebra)

smooth muscle cone: sympathetic innervation; contributes to globe position; tone pushes forward

Question 3

describe the eyelids

Answer 3

1. protection!
2. limit or exclude light
   -orbicularis oculi muscle closes lids (innervated by CN VII)
3. contribute to tear film (outer oily meibum layer)
   -spread tear film and remove foreign material

Question 4

describe eyelid clinical terms and landmarks

Answer 4

1. palpebral fissure: eyelid opening
2. medial and lateral canthi: corners where upper and lower eyelids meet
3. nasolacrimal puncta (upper and lower punctum)

Question 5

describe the 3rd eyelid

Answer 5

1. also called nictitans or nictitating membrane; lined by conjunctiva on both sides! palpebral outside in contact with lids; bulbar on backside
2. T shaped cartilage with horizontal and vertical portions- needs structure to squeegee
3. gland located at based of third eyelid, bulbar surface
4. contributes to tear film: middle serous/aqueous layer
5. movement from ventromedial to dorsolateral:
   -makes tears
   -spreads tears
   -physical protection to globe

Question 5

describe the nasolacrimal system

Answer 5

1. drainage system that removes tears from ocular surface bc constantly being produced; blink from lateral to medial to squeegee tears across eye surface to drain
2. components:
   -puncta: superior and inferior
   -canaliculi
   -lacrimal sac
   -duct

Question 6

describe conjunctiva

Answer 6

1. palpebral conjunctiva lines eyelids
2. bulbar conjunctiva covers the globe (bulb)
3. fornix is blind sac where they meet
4. third eyelid also lined by conjunctiva
5. goblet cells produce mucin (innermost layer of tear film)

Question 7

be able to label basic anatomy! see pic on slide

Answer 7

do it!

Question 8

describe the 3 concentric tunics/layers/coats of the eye

Answer 8

1. fibrous:
   -cornea continuous with sclera=outer layer
   -precorneal tear film!
   -cornea: optical element, protection
   -sclera (opaque): protection, determines shape of globe, site of insertion for extraocular muscles
2. uveal/vascular: iris (front most), ciliary body (middleish), choroid (innermost) all continuous with each other
   -middle layer
   -regulates light entering eye
   -site of blood eye barrier
   –blood aqueous barrier (iris, ciliary body)
   –blood retinal barrier (choroid)
   -produces aqueous humor (ciliary body)
3. nervous: retina, optic nerve
   -also continuous with back of iris but doesn’t do anything there

Question 9

describe the internal optic media

Answer 9

1. aqueous humor:
   -produced by ciliary body (non-pigmented epi)
   -fills anterior and posterior chamber
   -exits via iridiocorneal angle
   -flow obstruction results in increased intraocular pressure (glaucoma)
   -SEPARATE from serous (aqueous portion) of tear film!
2. lens
   -fine focusing of light/images onto retina (film of the camera)
   -held in place by zonules
   -antigenic protein: not recognized as “self”; if get out of lens and into eye could cause immune rxn
3. vitreous body
   -majority of volume of globe: contributes to shape, maintains retinal apposition (retina not physically attached in any way) with back of eye
   -transparent jello/jelly-like collagen-hyaluronic acid network despite being 98% water

camera!!