MANUAL PHYSIOLOGY PRACTICAL - Repository:The Medical ...

FM/UOJ
Test for colour blindness:
The cone pigments are essential for the perception of light by the cones. The gene
for the blue sensitive cone pigment is on chromosome 7 and the genes for green and red
sensitive pigments are on X chromosome. Because the red-green color blindness is sexlinked
recessive characteristics, females are generally carriers and males are the sufferers.
Detection of colour blindness is not easy because those who are deficient in color
vision has been also perceiving the rays and they were trained to call whatever the
sensation they got as the color. Various tests have been developed to identify colour
blindness.
Yarn-matching test:
This is a simple test. The subject is presented with a skein of yarn and asked to
pick out the one which matches the colour from a pile of various coloured skeins.
Ishihara charts:
These are series of charts produced by tricky color dots. The subject is asked to
read the number or trace the pattern in each chart and the interpretation of the response is
given in a booklet.
Experiment 2.7
Eye Reflexes
The activities of the eye are effected by skeletal and smooth muscles which are
supplied by somatic and autonomic nerves. Also several portions of the eye are rich in
sensory nerves and several reflexes can be demonstrated.
Protective reflex:
Ask the subject to look at a distance object. Bring an object (may be your hand)
rapidly towards the subjects eye. Observe the blinking of both eyes.
Corneal reflex:
Ask the subject to look ahead. Take a wisp of cotton wool and touch the cornea
gently by a side without bringing the wool in to sight. Observe blinking of both eyes.
Repeat the test by touching the conjunctiva and eyelashes.
Exercise: trace the pathway and describe the findings in possible lesions:
………………………………………………………………………………………………
………………………………………………………………………………………………
………………………………………………………………………………………………
………………………………………………………………………………………………
………………………………………………………………………………………………
………………………………………………………………………………………………
………………………………………………………………………………………………
Neurology
Page | 149