my own 2

• for what are responsible the eyes?

  for the sense of sight
• what have the eyes

  an eyeball protected by accesory glands and structures
• three layers of the eye


  retina, choroid and sclera
• name the parts of the eye

  vitreous humour, optic nerve, retina, choroid, sclera, crystalline lens, aqueous humour, cornea, iris, (pupil)
• name the accesory structures

  lacrimal glands, eyelids, eyebrows and eyelashes, and lacrimal sac
• how are images formed in the eye


  Light passes, cornea to the pupil. Opening, can increase or decrease in size, depending of the light. Crystalline lens adapts, bring the image into focus and projects it onto the retina. In the retina, light stimuli. Two types of photoreceptors: • Cones, colours • Rods, peripheral and low light.Photoreceptors in the retina transform the light stimulus into a nerve impulse. Optic nerve to the brain.
• hypermetropia


  Nearby objects are seen out of focus. • Eyeball is too short. • Images are formed behind the retina. • Convex lenses
• myopia

  Distant objects are seen out of focus. • Eyeball is too long. • Images are formed in front of the retina. • Concave lenses.
• astigmatism


  • Abnormal curvature of the cornea. • Multiple points of focus in the retina. • Special lenses.
• eye care measures

  • Glasses, avoid exposure to sunlight. • Avoid touching your eyes. • Adequate light, avoid reading in low light. • Limit the time in front of electronic devices.
• parts of the eye involved in sight

  Cornea, focuses the light. Iris/pupil (the hole). Controls the amount of light. Crystalline lens. Deformable lens, focuses the image in the retina. Retina. Detects light. Cones, they detect colours (R, G, B) and they need intense light. Roods, are sensitive, they do not differentiate colours.