The Visual System

Part 1

Glaucoma &

Glaucoma test

Refraction

Degree of cell packingin retina

Intrinsic Muscles of the Eye: The Iris

• Iris– circular.....constricts– radial.....…dilates

• Dilating pupil for eye exam: how to do it?

Pharmacology ofpupillary dilation:

Atropine

Intrinsic Muscles of the Eye:Ciliary Muscle

• Ciliary muscle relaxed = tension on zonular fibers = tension on lens = flattened lens = distant focus

• Ciliary muscle contracted = tension on zonular fibers reduced = less tension on lens = lens becomes more spherical =near focus

• Eye strain

Using a Microscope or Binoculars

With Convergence

1) DemonstrateConvergence

2) Measure NPA

Accommodation animation

NPA Left eye _______________mmNPA Right eye ______________ mm

Sex of subject ___ Age in months___

Normally use corrective lenses/contacts? yes/noWearing corrective lenses/contacts for test: yes/no

Presbyopia

0.06

0.070.080.09

0.160.140.12

0.18

0.30.4

Disorders of Focus

• Myopia = nearsighted– eyeball too long, cornea/lens to

“strong”– image focused in front of retina– correct with concave lens

• Hyperopia = farsighted– eyeball too short, cornea/lens to

“weak”– image focused behind retina– correct with convex lens

• Astigmatism– irregular surface of lens or cornea

Cataract

•

Extraocular muscles

• Motor innervation by CN III, IV, VI

Strabismus= misalignment of eyes

Storytime

             

Suprachiasmatic Nucleus for diurnal cycling

Visual reflexes:

Accomodation, Saccades,

Tracking, Pupillary reflexAka. Area 17 and V1

Goliath?

Evolution ofBinocular

VisionMapping the boundary of each visual field

Retinotopy

Point Localization Experiment• Work in pairs• 3 consecutive stimuli to same site• Trial 1 = Red pen• Trial 2 = Black pen• Trial 3 = Blue pen• Last digit SSN even = pen in dominant hand• Last digit SSN odd = pen in non-dom hand• 1st subject tests hand first• 2nd subject tests calf first• Test calf on same side as holding the marking pen.