optic pathway and its lesions (2).pptx

The optic nerve (CN II) is the second cranial nerve, responsible for transmitting the special sensory information for vision.

It is developed from the optic vesicle, an outpocketing of the forebrain. The optic nerve can therefore be considered part of the central nervous system, and examination of the nerve enables an assessment of intracranial health.

Due to its unique anatomical relation to the brain, the optic nerve is surrounded by the cranial meninges (not by epi-, peri- and endoneurium like most other nerves).

1. VISUAL PATHWAYS Dr. K. Ambareesha , PhD Assistant Professor, Department of Physiology, GMC, Secunderabad

2. SPECIFIC LEARNING OBJECTIVES Introduction Layers of Retina Visual pathway Order of neurons Retina Optic nerve Optic chaism Lateral geniculate nucleus Optic radiation Visual centres

3. A schematic of the anatomy of the eye

4. Layers of the Retina

5. Three order of neurons

6. Visual pathway

7. Retina

8. Optic Nerve

9. Optic Nerve

10. Optic Chaisma

11. Optic tract OPTIC TRACT

12. Lateral Geniculate nucleus (LGN)

13. Optic Radiation Optic Radiation

14. Projection of retina on primary visual cortex Medial view of the human right cerebral hemisphere showing projection of the retina on the primary visual cortex in the occipitalcortex around the calcarine fissure.

15. VISUAL CENTRES

16. Visual Cortex Representation of retina on the medial side of the occipital cortex (area 17)

17. Area 18 : visuaopsychic area (V2) Representation of area 17, 18 and 19 on the lateral surface of the occiptal lobe . MT, middle temporal, MST, medial superior temporal

18. Area 8: Frontal eye field Located@ Middle frontal gyrus It is concerned with voluntary conjugate deviation of eye s to the opposite side

19. Other areas

20. Projections from visual cortex Some of the main areas to which the primary visual cortex (V1) projects in the human brain. Lateral and medial views. LO, lateral occipital; MT, medial temporal; VP, ventral parietal.

21. Functions of visual projection areas in the human brain .

22. CONNECTIONS OF VISUAL PATHWAY

23. Connections

24. Connections

25. Connections

26. Optic pathway lesions A lesion that interrupts one optic nerve causes blindness in that eye (A ). A lesion in one optic tract causes blindness in half of the visual field (C) and is called homonymous (same side of both visual fields ) hemianopia (half-blindness). Lesions affecting the optic chiasm destroy fibers from both nasal hemiretinas and produce a heteronymous (opposite sides of the visual fields) hemianopia (B ). Occipital lesions may spare the fibers from the macula (as in D) because of the separation in the brain of these fibers from the others subserving vision.

27. Optic pathway lesions Anopia : Total loss of vision in one visual fields Hemianopia : Loss of vision in one half of visual field Homonymous : In the same halfs of both visual fields Heteronymous: In the opposite halves of both visual fields Quadranatanopia : Loss of vision in one foutrh of visual field. It can also be homonymous and heteronymous. Macular sparing: it is the unaffected amcular vision because of its bitemporal representation. Optic nerve Anopia Medial fibers of optic chiasma Heteronymous hemianopia ( Bitemporal ) Lateral fibers of optic chaism Heteronymous Hemianopia Optic tract Homonymous Hemianopia Optic radiation Homonymous Hemianopia with macular sparing Visual cortex Homonymous Hemianopia with macular sparing (Superior or inferior)

28. Summary

29. REFERENCES Berne & Levy Best and Taylor’s Boron Boulpaep G K pal

30. THANK YOU “The most pathetic person in the world is some one who has sight but no vision.” ―  Helen Keller