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How you see Light waves enter eye Light waves bend so as to focus on retina (refraction)

Refraction Cornea Aqueous humor Lens – change shape and refractive ability – Elastic structure – Fatter (bends at a sharper angle) or thinner – Held in place by suspensory ligaments attached to ciliary muscles

lens Over time, lens loses some of its ability to change shape – can’t accommodate to close objects

Role of the iris Pupil: regulating amount of light Acute vision

Retina Photoreceptors concentrated – Rods: concentrated in periphery, black and white, movement, respond to dim light – night vision. Vitamin A – Cones: color, heavily concentrated around central portion of retina, colored and sharp images,

translation Photoreceptors excited  nerve impulse  optic nerve  occipital lobe  “vision”

Focus: convergence Both eyes work together to form a single image “Lazy eye” – eyes not focusing on the same thing – occipital lobe can’t process both signals, suppresses images from the lazy eye, can lead to blindness

What three things help eyes focus on one object? Accommodation Pupillary constriction convergence

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