Refraction Glaucoma Glaucoma test Degree of cell packing

Refraction Glaucoma & Glaucoma test

Degree of cell packing in retina

Intrinsic Muscles of the Eye: The Iris • Iris – circular. . . constricts – radial. . . …dilates • Dilating pupil for eye exam: how to do it? Pharmacology of pupillary 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

Accommodation animation 1) Demonstrate Convergence 2) Measure NPA With Convergence

NPA Left eye ________mm NPA Right eye _______ mm Sex of subject ___ Age in months___ with corrective lenses/contacts? yes/no

Presbyopia

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 • Actions of extraocular muscles • Motor innervation by CN III, IV, VI Strabismus= misalignment of eyes Storytime

Suprachiasmatic Nucleus for diurnal cycling Visual reflexes: Aka. Area 17 and V 1 Accomodation, Saccades, Tracking, Pupillary reflex

Evolution of Binocular Vision Mapping the boundary of each visual field

Retinotopy

Goliath?

The Retina • Photoreceptors – Rods – Cones • Bipolar cells • Ganglion Cells – axons converge at optic disk – axons constitute optic nerve • Horizontal cells • Amacrine cells

Importance of abundant membrane

Visual Acuity • 120, 000 rods and 6, 000 cones per retina • 1, 200, 000 retinal ganglion cells & axons • 105: 1 convergence ratio • Fovea: cones only, 1: 1 highest visual acuity but poor sensitivity Counting fingers and Reading the Writing on the Wall

Demonstration of Blind Spot (diagram)

• Differences due to opsin: 4 types

Trichromatic Theory of Color Vision Web-based color deficiency test

Stargazing Finding your car in a dark parking lot Choosing socks

“Bleaching” of photopigments Visual Purple

The Dark Current

Phototransduction • In the DARK, rod is depolarized due to influx of Na+ (called dark current) • In the LIGHT, rod is hyperpolarized • c. GMP keeps Na+/Ca++ channels open • Light results in decrease of c. GMP and thus closure of ion channels, and • Hyperpolarization of cell, and • Reduced release of Neurotransmitter Glutamate

Properties of Cortical Neurons • Simple – respond to stationary bar of light in certain orientation • Complex – respond to moving bar of light in certain orientation • Hypercomplex – respond to moving bar of light of a certain length in a certain orientation

Parallel Processing in the Cortex • Motion sensitive • Color and shape sensitive Story of woman at street crossing

Why so much emphasis on the Visual System?