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Vision
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Anatomy of the Eye Fibrous tunic Sclera Cornea
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Anatomy of the Eye Vascular tunic = Uvea Choroid Ciliary body Iris
Pupil
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Anatomy of the Eye Nervous tunic = Retina & optic nerve
Outer pigmented layer Nervous layer
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Photoreceptors Rods Cones Macula Fovea centralis
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Optic Nerve Optic disc Blind Spot
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Anatomy of the Eye – Miscellaneous structures
Lens Anterior cavity Aqueous humor Posterior cavity Vitreous humor
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Anatomy – Accessory structures
Eyelids = Palpebrae Tarsal plate Meibomian glands Palpebral fissure Lateral commissure Medial commissure Caruncle Sebaceous ciliary glands
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Anatomy – Accessory structures
Conjunctiva Palpebral Bulbar
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Anatomy – Accessory structures
Lacrimal apparatus Function Lacrimal gland Lacrimal puncta Lacrimal canal Nasolacrimal duct
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Vision Light Refraction
Emmetropia = Normal vision, light rays focus on a single point called the Focal Point
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Focal Point
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Retina
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Vision Accommodation For close vision Pupils constrict
Eyeballs converge Near point of vision
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Vision Eye movement controls Voluntary fixation (premotor area)
Involuntary fixation (visual area)
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Vision Binocular vision Diplopia Strabismus
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Photoreceptors of Vision
Rods Rhodopsin is photopigment Numerous – about 120 million Sensitive to light Relative lack of color discrimination Peripheral retina in location Good for night vision, but poor detail Convergence
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Photoreceptors of Vision
Cones Few – about 6 million Photopigments sensitive to differing wavelengths of light 400 nm blue 500 nm green 600 nm red
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Photoreceptors of Vision
Cones High level of illumination Not very sensitive to light See in color Precise detail Little convergence Mostly in center of retina, esp. fovea
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Neural Components of Vision
Bipolar neurons Ganglion neurons Lateral inhibition Horizontal cells Amacrine cells
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Visual Acuity Snellen Eye Chart 20/20
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Light/Dark Adaptation
Photopigment concentration Pupillary light reflex PNS constricts pupil Direct – ipsilateral Indirect = Consensual - contralateral Cones inhibit rods in bright light
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Visual Pathway Optic Nerve Optic Chiasma Optic tracts
Thalamus – lateral geniculate body Occipital lobe of cerebral cortex
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