This document discusses defects of the visual pathway, including definitions of visual fields and how they are mapped. It describes how the image is inverted on the retina. Various types of visual field defects are defined such as scotomas, quadrantanopias, and hemianopias. Lesions along different parts of the visual pathway are described, including lesions of the optic nerve, optic chiasm, optic tract, lateral geniculate body, optic radiations, and visual cortex. The characteristics and causes of visual field defects resulting from lesions in each of these areas are provided.

1. Defects of visual pathway

5. Definition: The entire area that can be “seen”
by the patient without movement of the head
and with the eyes fixed on a single spot.
Visual Fields
Mapping of Visual Fields:
•Confrontational method
•Perimetry (Manual or Automated)

6. Visual Fields
The image of an object in the visual field is inverted and reversed right to left on the retina.
• Temporal field of left eye (red & purple) is seen by the nasal retina of the left eye
• Nasal field of the left eye (green & yellow) is seen by the temporal retina of the left eye.
• Superior field of the left eye (red & green) is seen by the inferior retina of the left eye.
• Inferior field of the left eye (purple & yellow) is seen by the superior retina of the left eye.
• Similarly, the image is inverted & reversed for the right eye.
Retina of Left
Eye
Retina of Right
Eye
Binocular
Visual Field
Monocular
Crescent of
Right Eye
Monocular
Crescent of Left
Eye

7. BLIND SPOT
• Corresponding to optic
nerve head
• 15 deg temporal to point of
fixation
• Span – 5 deg horizontal
-- 7 deg vertical

8. • SCOTOMA : focal region of abnormally
decreased sensitivity surrounded by an area of
normal sensitivity
– ABSOLUTE
– RELATIVE
– POSITIVE
– NEGATIVE

10. • QUADRANTANOPIA: Defective vision or blindness in approx.
one-fourth of the visual field
• HEMIANOPSIA: Defective vision or blindness in approx,. one-
half of the visual field
• HOMONYMOUS DEFECTS: Visual defects restricted to either
the right or the left visual field (post-chiasmatic defects)
• HETERONYMOUS DEFECTS: Visual defects involving parts of
both the left & right visual fields
• CONGROUS DEFECTS: Visual defects are equivalent in each
monocular visual field
• INCONGROUS DEFECTS: Visual defects are NOT equivalent in
each monocular field
• ALTITUDINAL DEFECTS: Visual defects are in the upper or lower
aspect of the visual fields

12. LESIONS OF VISUAL PATHWAY

13. 1) LESIONS OF OPTIC NERVE :
Causes:
• Optic atrophy
• Reterobulbar optic neuropathy
• Acute optic neuritis
• Traumatic
Characterised by: complete blindness in affected
eye with loss of both direct on ipsilateral &
concensual light reflex on contralateral side.
Near reflex is preserved.

15. 2)Lesions through proximal part of optic nerve :
• Ipsilateral blindness.
• Contralateral hemianopia
• Abolition of direct light reflex on affected side &
concensual light reflex on contralateral side.
• Near reflex intact.
Eg. Rt optic nerve
Involvement in
Proximal part

16. 3) Central lesions of chiasma (sagittal)
• Causes:
• Suprasellar aneurysm
• Tumors of pituitary gland
• Characterised by:
• Bitemporal hemianopia
• Bitemporal hemianopic
• Paralysis of pupillary reflex. (Usually lead to partial
descending optic atrophy)

18. 4)Lateral chiasmal lesions :
• causes:
• Distension of 3rd ventricle causing pressure on each
side of optic chiasma
• Atheroma of carotids & posterior communicating
artery.
Characterised by
• Binasal hemianopia
• Binasal hemianopic
• parallysis of pupillary reflex (usually lead to partial
descending optic atrophy)

19. 5)Lesions of optic tract :
Causes:
• Infections
• Tumors of optic thalamus
• Aneurysm of superior cerebellar or posterior cerebral
arteries.
Characterised by :
• Incongruous homonymous hemianopia with C/L
hemianopic pupillary reaction( wernicke’s reaction)
• These lesions usually lead to partial descending optic
atrophy & may be associated with C/L 3rd nerve
paralysis & ipsilateral hemiplegia.

21. 6)Lesions of lateral geniculate body :
 leads to homonymous hemianopia with
sparing of pupillary
reflexes & may end in
partial optic atrophy.

22. 7)Lesions of optic radiations :
Causes:
 Vascular occlusion
 Primary & secondary tumors
 Trauma
 Characterised by :
TOTAL OPTIC RADIATION
INVOLVEMENT
COMPLETE HOMONYMOUS
HEMIANOPIA( sometimes sparing
macula)

23. LESIONS OF PARIETAL LOBE (involving superior fibres of optic
radiations)
INFERIOR QUADRANTIC HEMIANOPIA( PIE ON THE FLOOR)
LESIONS OF TEMPORAL LOBE (involving inferior fibres of
optic radiations)
SUPERIOR QUADRANTIC HEMIANOPIA( PIE ON THE ROOF)

26. • Pupillary reactions are normal as fibres of light
reflex leave the optic tracts to synapse in the
superior colliculi.
• Lesions of optic radiations do not produce
optic atrophy as the 1st order neurons (optic
nerve fibres) synapse in LGB.

27. 8)Lesions of visual cortex : pupillary light
reflex is normal & optic atrophy does not occur
following visual cortex lesions.
Congruous
homonymous
hemianopia(sparing
macula)
Occlusion of posterior
cerebral artery
supplyin anterior part
of occipiatl cortex
Congruous
homonymous macular
defect
Head injury/gun shot
injury leading to
lesions of tip of
occipital cortex+