Download Physiology Practical

Physiology Practical.Dow University Of Health Sciences.
Field Of Vision and Perimetry:
Object:
To plot the field of Vision by Perimeter.
Learning Objectives:
At the end of the practical, the student should be able to:
a) Explain the procedure of Perimetry.
b) Draw the visual pathway.
c) Assess the lesions.
d) Know about diplopia and binocular vision.
e) See the blind Spot.
Requirements:
Perimeter,
Perimeter Chart and
Human Subject.
Perimeter Chart
Theoretical Explaination:
It may be divided into:
1. Temporal Field Of Vision = 90 °.
2. Nasal Field of Vision = 60 °.
3. Superior Field of Vision = 50 °.
4. Inferior Field of Vision = 80 °.
Field Of Vision
Field Of Vision:
Is the area seen by an eye at a given instant.
Visual Pathway:

Fibers Of Retina from nasal and temporal halves form optic nerve.

After nerve impulses leave the retinas, they pass backward through the optic nerve.

At the optic chiasma, all the fibers from the nasal halves of the retinas cross
to the opposite side, where they join the fibre from the opposite temporal
retinas to form the optic tract.

The fibres of each optic tract synapse in the dorsal lateral geniculate nucleus,
and from here, the geniculocalcarine fibre pass by the way of the optic
radiation to the primary visual cortex in the calcarine area of the occipital
lobe.

To diagnose blindness in specific portion of retinas chart the field of vision for each eye.

This is done by having a subject look towards a central spot directly in front of the eye.

Then a small dot of light or a small object is moved back and forth in all areas of the field of
vision and the person indicates when the spot of light or object can be
seen and when it cannot.

Thus the field of vision is plotted on perimeter chart.
Blind Spot:
In all perimeter charts, a blind spot caused by lack of rods and cone in the
retina over the optic disc is found approximately 15 degrees lateral to the
central point.
Binocular Vision:
The central part of the visual field of the two eyes
coincide, therefore anything in this portion of field is
viewed with binocular vision.
Fusion:
The impulses set up in two retinas by light rays from an object are fused at te cortical level into a
single image.
Corresponding Points:
The points on the retina on which the image of an object must fall, if it is to be seen binocularly as a
single object are called corresponding points.
Diplopia:
If one eye is gently pushed out of line while staring fixedly
at an object in the centre of visual field , double vision (
diplopia ) results .The image on the retina of the eye that
is displaces no longer falls on the corresponding point.