Glaucoma & Glaucoma test Refraction

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

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

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: Accomodation, Saccades, Tracking, Pupillary reflex Aka. Area 17 and V1

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 120,000,000 rods and 6,000,000 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

Web-based color deficiency test Trichromatic Theory of Color Vision

Stargazing Finding your car in a dark parking lot Choosing socks

Visual Purple “Bleaching” of photopigments

The Dark Current

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

Properties of Retinal Ganglion Cells Use MacRetina software to simulate experiments of Hubel & Wiesel (1960s) Determine location and shape of “receptive field” of an RGC.

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?