Eye Anatomy: Difficult Topics

Superior Rectus

elevation with adduction and medial rotation

-looking up

-CN III

Inferior Rectus

depression with adduction and lateral rotation

-looking down

-CN III

Lateral Rectus

abduction

-engages one eye at a time

-CN VI

Medial Rectus

adduction

-engages one eye at a time

-CN III

Superior Oblique

depression and abduction with medial rotation

-looks down and out, opposite of where it’s located

-CN IV

Inferior Oblique

elevation and abduction with lateral rotation

-looks up and out; opposite of where it’s located

-CN III

inferior oblique (right eye, CN III) and superior rectus (left eye, CN III)

What muscles are being engaged here?

lateral rectus (right, CN VI) and medial rectus (left, CN III)

What muscles are being engaged here?

Superior oblique (right, CN IV) and inferior rectus (CN III)

What muscles are engaged here?

Superior rectus and inferior oblique

What muscles are being engaged here?

Superior oblique and inferior rectus

What muscles are being engaged here?

Superior rectus (right, CN III) and inferior oblique (left, CN III)

What muscles are engaged here?

Medial rectus (right, CN III) and lateral rectus (left, CN VI)

What muscles are being engaged here?

Inferior rectus (right, CN III) and superior oblique (CN IV)

What muscles are being engaged here?

Optic Nerve

special sensory innervation from the retina to brain (vision)

Oculomotor Nerve

innervates the levator palpebrae superioris, sphincter/dilator pupillae, ciliary body, and 4/6 EO muscles

CN V-I

sensory to the upper/lateral eyelid; sensory innervation to the lacrimal gland, conjunctiva, cornea (corneal light reflex)

CN V-II

supplies sensory to the infra-orbital (lower eyelid) region

CN VII

visceral motor: parasympathetic innervation to the lacrimal gland (makes you cry)

motor: orbicularis oculi muscle

Uveal Tract

choroid, ciliary body, iris

Loosens, near

Accommodation of the lens: ciliary body contracts, _______ zonular fibers, shortens lens for _____ vision

Tighten, far

The ciliary body can also relax and _________ the zonular fibers, therefore flattening the lens and allowing for ___ vision

afferent, efferent, optic, oculomotor

Pupillary Light Reflex:

-Mediated by the optic (________) and oculomotor (________) nerves

-Incoming light > _____ nerve > pretectal area of midbrain > efferent impulses sent back to the eye through ____________ nerve > pupil constriction

Pigmented layer

single layer of melanocytes in the retina that helps absorb light rays, covers back side of iris and choroid too

Optic chiasm

If the patient had this visual defect, where would you expect a lesion to be?

Optic tract/radiation

If a patient presented with this focal deficit, where would you expect to find a lesion?

Optic nerve

If a patient presented with monocular blindness, where would you expect to find a lesion?

Left homonymous hemaniopia

If there is a lesion in the right optic track, what deficit would you expect the patient to display?

Right homonymous hemianopia

If there is a lesion found in the left optic tract, what deficit would you expect the patient to display?

Contralateral, ipsilateral

Information gathered from the nasal fields is processed on the _________ side of the brain, while information gathered from the temporal fields is processed on the _______ side of the brain

Blindness

Complete lesion of the optic nerve will cause _______

Bitemporal heteronymous hemianopia

A lesion in the optic chiasm will cause _______ __________ ________

Homonymous hemianopia

Destruction of one optic tract causes _________ _______, which is the complete loss of vision in the inner half of one eye and the outer half of the other

homonymous defect

Destruction of the optic radiation causes a __________ _____

Optic Nerve

-blindness in the affected eye

-monocular blindness

Optic chiasm

-loss of fibers crossing the midline from the nasal half of each retina causes loss of temporal visual field on both sides

-bitemporal heteronymous hemianopia

Optic tract

-loss of fibers for the visual field on the opposite side of the lesion

-homonymous hemianopia

Optic radiation

-loss of fibers for the visual field on the opposite side to the lesion

-homonymous hemianopia

Visual cortex (one side)

-loss of visual processing for the visual field on the opposite side to the lesion

-homonymous hemianopia with macular sparing

Accommodation

allows for focusing on nearby objects, lens shortens

Convergence

active process of turning the eyes inward to maintain alignment of the visual axes with an object

Strabismus

one of the extraocular eye muscles are not working, therefore affecting convergence

Myopia

globe is too long

near is clear, distant blurry = nearsightedness

corrected by concave lens

Hyperopia

globe too short

near blurry, distant clear = farsightedness

corrected by convex lens

Presbyopia

lens is unable to increase its refractive power, becomes more rigid

-can’t accommodate on near objects

-vision changes due to age

20/200, 20

Legal Blindness:

1. Best corrected acuity of __/___ or less in the better eye

2. Binocular visual field of __ degrees or less