Vision Physiology

Question 1

Vision Physiology

Answer 1

-the function of the eye is to transform light energy into nerve signals that can be transmitted to the cerebral cortex for interpretation

Question 2

Pupillary Reflex

Answer 2

-Autonomic Nervous Systems

-Cranial Nerves II & III
optic nerve
oculomotor nerve controls inferior, medial, superior, rectus and inferior oblique muscles of eye

• sphincter pupillae-close vision & bright light -constrict pupil (circular muscle)
• dilator papillae-distant vision & dim light pupil dilates (radial muscle)

circular muscle = constricts pupil
radial muscle = dilates pupil

Question 3

Control of Pupil Diameter

Answer 3

• stimulation of parasympathetic nerve EXCITES the pupillary sphincter muscle, thereby decreasing the pupillary aperture (miosis)
• sympathetic stimulation, conversely, dilates the pupil (mydriasis)
• light shine constricts pupils (pupillary light reflex) -functions to allow adaption with rapid changes in light

Question 4

Constriction (parasympathetic)

Answer 4

Edinger-Westphal Nucleus of 3rd Nerve –> ciliary ganglion –> constriction in circular muscle

Question 5

Dilation (sympathetic)

Answer 5

Spinal Cord –> Superior Cervical Ganglion –> radial muscle dilates

Question 6

What is being tested? 
Direct Response (pupil illuminated)

Answer 6

direct response is impaired in lesions of the
ipsilateral optic nerve
pretectal area
ipsilateral parasympathetics traveling in CN III
pupillary constrictor muscle of iris

(any damage to those areas –> loss of function)

Question 7

What is being tested?
Consensual Response
(contralateral pupil is illuminated)

Answer 7

consensual response is impaired in lesions of the

• contralateral optic nerve
• pretectal area
• ipsilateral parasympathetics traveling in CN III
• pupillary constrictor muscle

Question 8

What is being tested?
Accommodation
(response to looking at something moving towards the eye)

Answer 8

accommodation is impaired in lesions of the

• ipsilateral optic nerve
• ipsilateral parasympathetics traveling in CN III
• pupillary constrictor muscle
• bilateral lesions of the pathways from the optic tracts to the visual cortex

-accommodation is spared in lesions of the pretectal area

ispilateral =same side
contralateral =opposite side