MANUAL PHYSIOLOGY PRACTICAL - Repository:The Medical ...

FM/UOJ
Test for near vision:
Jaeger’s chart or Rayner test types chart is used. These are made of letters of
different sizes. The subject starts at the smallest and goes on trying to read bigger letters.
The chart should be kept at about 35 cm. from the eye.
Test for astigmatism
The chart with parallel lines radiating from a central point is observed by the
subject. All lines will be alike if no astigmatism and certain lines will be blurred while
others remain clear if the defect is present.
Exercise: list the visual defects and the lenses used to correct them.
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Experiment 2.6
Color Vision
Color vision is a complex function which involves retinal and cortical functions.
Presence of three types of cones which respond maximally to blue, green and red (yellow)
and the fact that these colours could be mixed to produce any color sensation forms the
basis for the three primary colours. Even though the three types of cones respond
maximally to specific colours, they respond at various levels to all light rays in the visual
range of wave length. The final perception of color, therefore, appears to be the
integration of the impulses from all cones by the cortical areas.
Demonstration of complementary colour:
Place a rectangular sheet of any color in well illuminated white background. Fix
the gaze on the sheet for two minutes without moving the eyes. Remove the sheet of
paper suddenly (preferably by another person). For a few seconds a different colour
comes into view and fades off. This color is the complementary colour for the colour of th
sheet. Repeat the test with different colours and determine the complimentary colour for
all colours.
Neurology
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