Vision II

• What is the eye with normal refractive power called?

  Emmetropic eye
• What is the condition called when the eye has normal refractive power?

  Emmetropia
• What does the term "errors of refraction" refer to?

  Deviation in refractive power from normal
• What is myopia also known as?

  Short sightedness
• What characterizes myopia?

  Inability to see distant objects
• How does the anterio posterior diameter of the eyeball affect myopia?

  It is abnormally long in myopia
• Where is the image focused in myopia?

  In front of the retina
• What type of lens corrects myopia?

  Biconcave lens
• What is hypermetropia also known as?

  Long sightedness
• What characterizes hypermetropia?

  Inability to see near objects
• What causes hypermetropia?

  Decreased anterio posterior diameter of eyeball
• Where are light rays focused in hypermetropia?

  Behind the retina
• What type of lens corrects hypermetropia?

  Biconvex lens
• What causes astigmatism?

  Uneven corneal surface or lens curvature
• What is the effect of astigmatism on vision?

  Causes blurring of image
• How is astigmatism corrected?

  Using a cylindrical lens
• What is presbyopia?

  Diminished ability to focus on near objects
• What causes presbyopia?

  Reduction in amplitude of accommodation
• What vision is unaffected in presbyopia?

  Distant vision
• How is presbyopia corrected?

  Using a biconvex lens
• What is the visual pathway?

  Nervous pathway from retina to cortex
• What happens in binocular vision?

  Both eyes see a portion together
• What are the visual receptors in the retina?

  Rods and cones
• What are first order neurons in the retina?

  Bipolar cells
• What are second order neurons in the visual pathway?

  Ganglionic cells
• What do the axons of ganglionic cells form?

  Optic nerve
• Where do optic tracts terminate?

  Lateral geniculate body
• What do fibers from the lateral geniculate body reach?

  Visual cortex as optic radiations
• What is anopia?

  Loss of vision in one visual field
• What is hemianopia?

  Loss of vision in one half of visual field
• What does homonymous hemianopia mean?

  Loss of vision in same halves of both fields
• What does heteronymous hemianopia mean?

  Loss of vision in opposite halves of visual field
• What happens with a lesion in one optic nerve?

  Causes total blindness in corresponding field
• What does a lesion of optic tract cause?

  Homonymous hemianopia
• What does a lesion in the upper or lower visual cortex lead to?

  Inferior or superior homonymous hemianopia
• What is macular sparing?

  Macular vision retained in hemianopia
• What are pupillary reflexes?

  Reflexes that alter the size of pupil
• What are the two types of pupillary reflexes?

  Light reflex and accommodation reflex
• What happens during the light reflex?

  Pupil constricts when light is flashed
• What is direct light reflex?

  Pupil constricts in the eye with light