Understanding Refraction, Glaucoma, and Eye Muscles: A Comprehensive Guide

2. Refraction Glaucoma & Glaucoma test

4. Degree of cell packingin retina

5. 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

6. 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

7. Accommodation animation • DemonstrateConvergence • Measure NPA With Convergence

8. NPA Left eye _______________mm NPA Right eye ______________ mm Sex of subject ___ Age in months___ with corrective lenses/contacts? yes/no

9. Presbyopia

10. 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

11. Cataract

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

14. Visual reflexes: Accomodation, Saccades, Tracking, Pupillary reflex Suprachiasmatic Nucleus for diurnal cycling Aka. Area 17 and V1

15. Evolution ofBinocular Vision Mapping the boundary of each visual field

16. Retinotopy

17. Goliath?

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

19. Importance of abundantmembrane

20. 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 andReading the Writing on the Wall

22. Demonstrationof Blind Spot (diagram)

23. Differences due to opsin: 4 types

24. Trichromatic Theory of Color Vision Web-based color deficiency test

25. StargazingFinding your car in a dark parking lotChoosing socks

26. “Bleaching” of photopigments Visual Purple

27. The Dark Current

29. 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

32. 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

34. Parallel Processing in the Cortex • Motion sensitive • Color and shape sensitive Story of woman atstreet crossing

35. Why so much emphasis on the Visual System?