This document provides an overview of the visual pathway, which transmits visual impulses from the retina to the visual cortex of the brain. It describes the main components of the visual pathway, including rods and cones, bipolar cells, ganglionic cells that form the optic nerve, the lateral geniculate body, optic radiation and visual cortex. It also discusses lesions that can occur at different points along the visual pathway and the visual field defects they may cause, such as homonymous hemianopia.

1. Venkatesh Karthikeyan
II MBBS
Velammal Medical College

2. Interpret!
 30 year old patient Mr.Siddarth , a
known case of Syphilis, presented to
Department of Ophthalmology, VMCH
with complaints of partial loss of
vision.What type of visual field defect
you suspect ? Why?

3. Interpret!
 40 year old patient
Mr.Aathreya, a known
diabetic and hypertensive,
presented to Department of
Ophthalmology, VMCH with
complaints of partial loss of
vision in his left eye. He is a
cigarette smoker for past 20
years.

4. What is Visual Pathway?
 Visual pathway or optic pathway is the
nervous pathway that transmits impulses
from retina to visual centre in cerebral
cortex.

9. VISUAL RECEPTORS
 Rods and cones
 They synapse with dendrites of bipolar
cells of inner nuclear layer of the retina.

10. FIRST ORDER NEURONS
 First order neurons (primary neurons)
are bipolar cells in the retina.
 Axons from the bipolar cells synapse
with dendrites of ganglionic cells.

11. SECOND ORDER
NEURONS
 They are the ganglionic cells in
ganglionic cell layer of retina.
 Axons of the ganglionic cells form optic
nerve.
 Optic nerve leaves the eye and
terminates in lateral geniculate body.

12. THIRD ORDER NEURONS
 They are in the lateral geniculate body.
 Fibres arising from LGB, reaches the
visual cortex.

13. OPTIC NERVE
 Formed by the axons of ganglionic cells
 It leaves the eye through optic disc.
 The fibers from temporal part of retina
are in lateral part of the nerve and carry
the impulses from nasal half of visual
field of same eye and vice versa.

14. „OPTIC CHIASMA
 Medial fibers of each optic nerve cross
the midline and join the uncrossed
lateral fibers of opposite side, to form
the optic tract.

15. Optic Tract
 Formed by uncrossed fibers of optic
nerve on the same side and crossed
fibers of optic nerve from the opposite
side.
 The fibers turn around the peduncle to
reach the lateral geniculate body in
thalamus.

16.  Here, many fibers synapse while few
fibers just pass through this and run
towards superior colliculus in midbrain.
 Fibers from fovea do not enter superior
colliculus.

17. LATERAL GENICULATE
BODY
 Majority of the fibers of optic tract
terminate in lateral geniculate body,
which forms the subcortical center for
visual sensation.
 From here, the geniculocalcarine tract
or optic radiation arises.

18. Other relay centres
 Superior colliculus:
 Concerned with reflex movements of eyeballs and
head, in response to optic stimulus
 Pretectal nucleus:
 Concerned with light reflexes
 Supraoptic nucleus of hypothalamus:
 It is concerned with the retinal control of pituitary
in animals. But in human, it does not play any
important role.

19. Optic Radiation
 Fibers from lateral geniculate body pass
through internal capsule and form optic
radiation.
 The fibers between lateral geniculate body
and visual cortex are also called
geniculocalcarine fibers.
 Optic radiation ends in visual cortex

20. Visual Cortex
 Primary visual area (17) - Perception of
visual impulses
 Secondary visual area (18) -
Interpretation of visual impulses
 Occipital eye field (19) - Movement of
eyes.

23. Visual Pathway lesions
 Hemianopia : Blindness over half the
field of vision.
 Homonymous : Visual field loss on the
same side of both eyes.

25. Causes of Optic Nerve
Lesion
 Optic atrophy
 Traumatic avulsion of the optic nerve
 Indirect optic neuropathy
 Acute optic neuritis

26. Lesions of Chiasma
 Suprasellar aneurysms
 Tumours of pituitary gland
 Third ventricular dilatation due to
obstructive hydrocephalus
 Atheroma of the carotids or posterior
communicating arteries

27. Optic tract lesions
 Syphilitic meningitis
 Tuberculosis and tumours of optic
thalamus
 Aneurysms of superior cerebellar or
posterior cerebral arteries.

28. Lesion in Optic Radiation
 Vascular occlusions
 Primary and secondary tumours
 Trauma

29. Homonymous Hemianopia

30. Upper Homonymous
Quadrantanopia

31. Lower Homonymous
Quadrantanopia

32. Interpret!
 30 year old patient Mr.Siddarth , a
known case of Syphilis, presented to
Department of Ophthalmology, VMCH
with complaints of partial loss of
vision.What type of visual field defect
you suspect ? Why?
 Homonymous hemianopia due to Optic
tract lesion

33. Interpret!
 40 year old patient
Mr.Aathreya, a known
diabetic and hypertensive,
presented to Department of
Ophthalmology, VMCH with
complaints of partial loss of
vision in his left eye. He is a
cigarette smoker for past 20
years.
 Homonymous hemianopia
with macular sparing!

34. Thank you 