Perimetry & Effects of lesions at different levels of VISUAL PATHWAY for MBBS Students as well as for Medicos

1. PERIMETRY &
EFFECTS OF LESION AT DIFFERENT LEVELS OF
VISUAL PATHWAY
Pandian. M
D.Y. Patil Medical College, Kolhapur.

2. INTRODUCTION
1. Perimetry is the method of accurate charting of peripheral field of
vision.
2. Perimetry is the procedure to map the field of vision of each eye
separately.
3. Clinically, the field of vision is determined by confrontation method. It
gives rough idea about field of vision.
4. Perimetry is performed to detect the exact nature and extent of defects in
field of vision.
5. The defects in the field of vision occurs due to lesions at various levels of
visual pathway.

3. FIELD OF VISION Vs BINOCULAR
FIELD OF VISION
•Field of vision : It is the part of the external world that
is seen with one eye when the gaze is fixed on a particular
object.
•Binocular field of vision : It is the field of vision
which is common to both the eyes.

4. DIFFERENT TYPES OF PERIMETRY
1. Priestley – Smith’s Perimetry
2. Lister’s perimetry *
3. Student perimetry **
4. Maroitte’s experiment

6. LISTER’S PERIMETRY *

7. • Perimetry is the procedure to map the field of vision of each eye
separately. The instrument viz
The Lister's perimeter consists of following parts :
1. A metallic arc with movable object (white or colored) of 10 mm X 10
mm size. The arc is graduated from zero degree in the centre to 90 degrees
at the periphery.
2. A stand to support the arc.
3. A chin rest attached to platform.
4. A graduated disc to read the meridian.
5. A circular ring to fix the perimeter chart at the back of the disc.
6. A rod to align the eye with the central white spot on the disc.

8. Meyer’s loop

11. Procedure :
• Confrontation test is done before perimetry to get rough idea of
field of vision.
A. Confrontation test:
B. Perimetry:
C. To find out the blind spot:

13. NORMAL FIELD OF VISION :
• Temporal side: 100 degree (there is no anatomical obstruction on the tempo.
Side the Field in this quadrant is more)
• Superior side: 55 degrees (supraorbital margin provides anatomical
obstruction ↓ Field in this quadrant )
• Nasal side: 60 degrees ( nasal bridge provides anatomical obstruction ↓
Field in this quadrant)
• Inferior side: 75 degrees ( maxilla of cheek provides anatomical obstruction
↓ Field in this quadrant)

14. BLIND SPOT
• In the temporal side of the fixation point abt 12 ̊ – 15 ̊ a
scotoma (blind spot) is located where perception of light does
not occur.
• Due to absence of Rods and Cones.
• So, called Physiological scotoma and corresponds to the optic
disc in retina.
• It measures approx. 7.5 ̊ in height & 5.5 ̊ in width.
• The visual field of both eyes overlap in medial part to form the
area of binocular vision

15. SOME CAUSES OF SCOTOMA
1. Unilateral scotoma seen in – demyelination of optic nerve,
glaucoma
2. Bilateral scotoma causes are: alcoholism, Vit B12 deficiency,
lesion in Visual cortex.

17. Lesions of the visual pathways at the
level of:
1. optic nerve;
2. proximal part of optic nerve;
3. central chiasma;
4. lateral chiasma (both sides);
5. optic tract;
6. geniculate body;
7. part of optic radiations in temporal
lobe;
8. part of optic radiations in the parietal
lobe;
9. optic radiations;
10. visual cortex sparing the macula and
11. visual cortex, only macula.

19. FIELDS DEFECTS IN LESIONS OF
VISUAL PATHWAY
1. Lesions of the optic nerve.
-These are characterized by a marked loss of vision or
complete blindness on the affected side
- associated with abolition of the direct light reflex on the
ipsilateral side and consensual light reflex on the contralateral
side.
-Near (accommodation) reflex is present.

20. 2. Lesions through proximal part of the optic nerve.
• Salient features of such lesions are: ipsilateral blindness,
• contralateral hemianopia and abolition of direct light reflex
• on the affected side and consensual on the contralateral side.
• Near reflex is intact.

21. • 3. Sagittal (central) lesions of the chiasma.
• These are characterized by bitemporal hemianopia and bitemporal
hemianopic paralysis of pupillary reflexes.
• Common causes of central chiasmal lesion are: suprasellar aneurysms
and tumours of pituitary gland.

22. • 4. Lateral chiasmal lesions.
• Salient features of such lesions are binasal hemianopia associated with
binasal hemianopic paralysis of the pupillary reflexes.
• Common causes of such lesions are distension of third ventricle causing
pressure on each side of the chiasma.

23. • 5. Lesions of optic tract.
• These are characterized by homonymous hemianopia
associated with contralateral hemianopic pupillary
reaction (Wernicke’s reaction).
6. & 9 Lesions of lateral geniculate body.
These produce homonymous hemianopia with
sparing of pupillary reflexes.

24. • 7 & 8 Lesions of optic radiations.
• Their features vary depending upon the site of
lesion.
• Involvement of total optic radiations produces
complete homonymous hemianopia
(sometimes sparing the macula).
• Inferior quadrantic hemianopia (pie on the
floor) occurs in lesions of parietal lobe
(containing superior fibres of optic radiations).
• Superior quadrantic hemianopia (pie in the
sky) may occur following lesions of the
temporal lobe (containing inferior fibres of
optic radiations).

25. • 10 & 11. Lesions of the visual cortex.
• Congruous homonymous hemianopia (usually sparing the
macula) is a feature of occlusion of posterior cerebral artery
supplying the anterior part of occipital cortex.
• Congruous homonymous macular defect occurs in lesions of the
tip of the occipital cortex following head injury or gun shot
injuries.
• Pupillary light reflexes are normal and optic atrophy does not
occur following visual cortex lesions.

26. • Lesions of visual area 18 and 19.
• The visual sensibility remains intact but there is disturbance in
higher visual functions (visual agnosia).

27. FACTORS AFFECTING F.V.
1. Color of the object – better when using white color less in
Blue or red
2. Size of the object – larger size better in Visual acuity but std
size for perimetry.
3. Brightness of the object - brightness, contrast &
illumination affects both V. A & F.V.
4. Illumination – poor illumination decreases the V.F

28. PRECAUTIONS1. Instruction
2. Read the chart
3. Examination of eye
4. Fixation of the eye (gaze)
5. Repeat the procedure at 15 ̊ interval
6. Mapping should be in clock wise
7. Blind should be marked in horizontal meridian in temporal quadrant
8. F.V should test both eyes separately.
9. Illumination should be adequate
10.The subject should remove his/her glasses, if he normally uses them,
otherwise the filed of vison will be restricted

29. OBSERVATION
•Observe the obtained field of vision &
compare it with the normal visual field
depicted in this chart.
•Note the site and size of the blind spot

30. REFERENCES
• D.Y. Patil Medical College Journal
• Text book of Practical Physiology
-By G.K. Pal
• Text book of Practical Physiology
-By A.K. Jain.
• Text book of Practical Physiology
-By C.L. Ghai
• Net source (For pic & etc.)

31. THANK YOU . . .