21.1 NS: Orbit and eyes

Question 1

Michael is a karate black belt and receives a hit to the eye. He notices he has double vision. What type of injury is this?

Answer 1

A blow out orbital fracture

Question 2

What are the supra and infrorbital margins formed by?

Answer 2

Supraorbital: frontal bone
Infrorbital: Laterally-zygomatic, medially-maxilla

Question 3

What can be injured in a poke to an eye? (Symptoms are pain, double vision, red watery eye)

Answer 3

Corneal injury

Question 4

What is the outer layer of the globe? What do these components do?

Answer 4

Cornea (refraction), sclera (shape, muscle attachment)

Question 5

What is the anterior chamber angle? What does it do?

Answer 5

Junction between iris and cornea (where aqueous humour drains)

Question 6

How many layers does the cornea have? Why is it transparent?

Answer 6

5 layers

Collagen fibrils run parallel in bundles (lamellae)

Question 7

What structure in the AC angle releases AH, and where does it flow out?

Answer 7

Ciliary body releases AH, then drains out the canal of Schlemm

Question 8

What are the components of the middle coat of the globe?

Answer 8

Uvea (ciliary body, iris, choroid)

Question 9

What is presbyoipia?

Answer 9

Loss of accommodation with age (inflexible lens)

Question 10

What is the ciliary musucle innervated by? Where is it found?

Answer 10

PSNS, found in the ciliary body

Question 11

When focusing on a close object, what does the lens/ciliary muscle and zonules do?

Answer 11

To focus light:
Ciliary muscle contracted
Lens bulges
Relaxed wavy zonules

Question 12

What are the muscles that control pupil dilation and constriction? What are they innervated by?

Answer 12

Dilation: dilator pupillae (SNS)
Constriction: sphincter pupillae

Question 13

What supplies nutrients to the retina?

Answer 13

The choroid

Question 14

What does the fovea have a high density of? Is it vascular?

Answer 14

High density of cones

Avascular (nutrients from choroid)

Question 15

What is the optic nerve formed by?

Answer 15

Axons of ganglion cells exiting the retina

Question 16

What could a curtain coming down over vision in one eye be due to?

Answer 16

Arterial occlusion at the macula

Question 17

What is the blood supply to the orbit? What are its branches?

Answer 17

Ophthalmic artery (branches: central retinal artery, ciliary arteries)

Question 18

What is the blood supply to the retina?

Answer 18

Dual

Inner retina: CRA

Outer retina (photoreceptors): posterior ciliary artery

Question 19

What are the muscles of the eyelid? What do they do and what are they innervated by?

Answer 19

Orbicularis oculi:
Depresses lid (CNVII)

Levator palpebrae superioris: Elevates lid (CNIII)