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									SPECIAL
SENSES:
VISION 05


Tanveer Raza MD MS MBBS
   razajju2@yahoo.com
Visual pathway




                 Tanveer Raza MD MS MBSS
                        razajju2@yahoo.com
Visual pathway




                 Tanveer Raza MD MS MBSS
                        razajju2@yahoo.com
Lesions in the Visual pathway
   Optic nerve       Blindness of affected eye
   Crossed fibers    Bitemporal hemianopia
   Uncrossed fiber   Binasal hemianopia
   Optic tract       Homonymous hemianopia




                               Tanveer Raza MD MS MBSS
                                      razajju2@yahoo.com
Visual pathway




                 Tanveer Raza MD MS MBSS
                        razajju2@yahoo.com
Tanveer Raza MD MS MBSS
       razajju2@yahoo.com
Adaptation
 Ability of eye to adjust to various levels
 of darkness and light
   Light adaptation
      When we move from dark into bright light
   Dark adaptation
      When we move from bright into dark light




                              Tanveer Raza MD MS MBSS
                                     razajju2@yahoo.com
Adaptation
Dark Adaptation
              20 minutes




                            Visual threshold
Light Adaptation
              5 minutes




                           Visual threshold
                               Tanveer Raza MD MS MBSS
                                      razajju2@yahoo.com
Adaptation
 Components
  1. Adaptation of the rods and cones
  2. Pupillary size
  3. Neural adaptation




                               Tanveer Raza MD MS MBSS
                                      razajju2@yahoo.com
 Adaptation
 Adaptation of the rods and cones




                        Dark adaptation,
                        demonstrating the
                        relation of cone
                        adaptation to rod
                        adaptation

                           Tanveer Raza MD MS MBSS
                                  razajju2@yahoo.com
Rhodopsin (visual purple)
  Rhodopsin      Retinal                  Scotopsin
                 (11-cis retinal)



 Retinal
   Carotenoid pigment
 Scotopsin
   Protein



                                    Tanveer Raza MD MS MBSS
                                           razajju2@yahoo.com
        Activated
        rhodopsin
        Excites electrical
        changes



        Form of vitamin A
Tanveer Raza MD MS MBSS
       razajju2@yahoo.com
Night Blindness (Nyctalopia)


 Severe Vitamin A
 deficiency

 Amount of light
 available at night is to
 little to permit
 adequate vision in
 Vitamin A deficient
 person

                            Tanveer Raza MD MS MBSS
                                   razajju2@yahoo.com
Reflexes of the eye
1. Light reflex
2. Accommodation reflex
3. Visual reflex
4. Corneal or/and Conjunctival reflex




                            Tanveer Raza MD MS MBSS
                                   razajju2@yahoo.com
Reflexes of the eye
1. Light reflex
     Direct light reflex
     Consensual light reflex
2. Accommodation reflex
    1. Convergence of eye ball
    2. Modification of lens shape
    3. Constriction of pupil
3. Visual reflex
4. Corneal or/and Conjunctival reflex



                                        Tanveer Raza MD MS MBSS
                                               razajju2@yahoo.com
Reflexes of the eye
1. Light reflex
2. Accommodation reflex

3. Visual reflex
     Sudden training of the head, neck and
     upper part of the trunk towards a sudden
     flash of light
4. Corneal or/and Conjunctival reflex
    Slight touching results in blinking of
     eyelids


                                Tanveer Raza MD MS MBSS
                                       razajju2@yahoo.com
Reflexes of the eye
 Corneal Reflex




                      Tanveer Raza MD MS MBSS
                             razajju2@yahoo.com
Thank You

								
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