HTHSCI 1H06 Lecture Notes - Lecture 4: Near-Sightedness, Presbyopia, Aqueous Humour
28 Feb 2018
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Document Summary
6 cranial nerves involved in vision: 2 sensory, 4 motor. Cn 2 (light detection in the eye) Cn 3, 4, 6 (moves the eyeball around) Lens adjusts the focus of the eye (20% refraction done by the lens). Bends 80% of light and projects it to the back of the eye. Is clear bc the collagen fibres run in the same direction and no water in the cornea"s connective tissue (epithelium and endothelium). Conjunctiva a mucous membrane, lines interior of eyelid and surface of sclera. Tears keep it clean, via the lacrimal glands. Tarsal gland secretes oil that floats to the top of water and prevents evaporation of tears. Hyperopia eye is flattened, visual pathway is elongated. Light is projected behind the eye to produce a fuzzy image close up (farsightedness). Myopia eye is elongated, visual pathway is shortened. Light falls too short, doesn"t reach the back of the eye, produces a fuzzy image far away (nearsightedness).
