visual pathway of human anatomy for medical and par medical students

anatomy of visual path

1. VISUAL PATHWAY

2. Visual pathway Introduction. Structures which transmit the visual images from eyeball to visual cortex.

3. Parts Eye ball Retina Optic nerve Optic chiasma Optictract Lat.geniculate body Optic radiation Visual cortex Area 17,18,19.

4. Eye ball

5. Layers of retina Axons of the ganlion cell layer forms the optic nerve.

6. Visual field and retina Temporal visual field fall on nasal retinal field. Nasal visual falls on temporal retinal field.

7. Visual field in different part of visual pathway.

8. Optic nerve Outgrowth of brain-white matter Stalk of optic vesicle 2 nd cranial nerve 4 cm length 3 parts-25mm,5mm, 10mm 3 coverings, 2 spaces 800 to 1000 –polygonal bundles, 1.2 million fibers,92% 1micron-10m/s, rest2-10mic-60m/s Devoid - neurolemma

9. Optic nerve con… Myalinated by oligodentroglia Pierce lamina cribosa at 3mm medial to posterior pole. For easy movements Intra orbital part length is 6mm more than the distance bt the eye ball and optic canal.

10. Optic nerve con… 12 mm behind the eye ball it pierced by central artery and vein. Intra cranial pressure leads to papilloedema and choked disc. Relations: orbital part

11. Canalicular part of optic nerve 5 mm length Relations: infero laterally ophthalmic artery, medially by- post.ethmoidal air sinus and sphenoidal air sinus separated by thin plate of bone. Infection lead-retro bulbar optic neurities . SR,LR-origin from bone-leads to pain at elevation and adduction

12. Intra cranial part of optic nerve 10mm length Relations- Above- pos.part of olfactory tract, gyrus rectus and ant.cerebral artery. Laterally – int.carotid artery. Inferiorly- sphenoidal air sinus

13. Nerve fibres arrangement in optic nerve Nerve fibres arrangement in anterior and posterior part of the intra orbital part of the optic nerve.

14. Blood supply sup.hypophysial artery,ophthalmic artery, post.ciliary artery, central artery of retina.

15. Optic nerve lesion Total blindness corresponding side. Loss of direct light reflex same side. Loss of consensual light reflex on normal side. Retention of consensual light reflex on affected side. Retention of direct light reflex on normal side.

16. Optic nerve lesion con.. Frontal lobe base tumour leads to foster kennedy syndrome. Foster Kennedy syndrome (FKS) is characterized by visual loss due to compressive optic atrophy in one eye and papilledema in the contralateral eye brought on by increased intracranial pressure.

17. Optic chiasma Looks above-flat Transverse-oval in shape 53% crossed fibres 47% uncrossed fibre Relations: Sup:3 rd ventricle Lat : ICA Ant: anterior cerebral artery, ant.commu.artery Post: interpeduncular fossa,tuber cinerium,infundi.pituitary . Inf : sphe.air sinus

18. Willbrand’s loop in optic chiasma

19. Lesion in optic chiasma Bitemporal hetronymous hemianopia. Binasal het-hemianopia Inferior fibres loss- bitemporal superior quadrant anopia . Superior fibres loss- bitemporal inferior quadrant anopia .

20. Optic tract Extend from optic chiasma to lateral geniculate body. Two roots-lateral and medial root. Lateral root end in lateral geniculate body and superior colliculi . Medial root end in medial geniculate body forms supra optic commissure fibers .

21. Blood supply anterior choroidal artery, middle cerebral artery, post.commu.artery , ICA

22. Lateral geniculate body Present in the postero -lateral part of the pulvinar of the thalamus. Kidney shape-hilum facing inferiorly. Has 6 layers. Temporal fibres end in 2,3,5 layers. Nasal fibres end i1,4,6 layers.

23. Lateral geniculate body con..

24. Lesion in lateral geniculate body Loss of vision results in a characteristic visual field defect, typically causing a contralateral homonymous hemianopia or quadrantanopia , meaning a loss of vision in the same half of the visual field in both eyes on the opposite side of the brain where the lesion is located Light reflex retained

25. Optic radiation ( geniculo calcarine tract) Extend from LGB to visual cortex. Medial part of LGB-Superior retinal quadrant-reach sup.lip of calcarine sulcus. Lateral part of LGB-Inferior retinal quadrant –reach inferior lip of calcarine sulcus

26. Optic radiation con… Has three group of bundles. Mayers loop Central bundle Dorsal bundle

27. Optic radiation con… Blood supply: anterior choroidal artery, middle cerebral artery and posterior cerebral artery.

28. Visual path defects

29. Lesion in pretectal nucleus Argyll robertson pupil Loss of light reflex Accommodation reflex retained.

30. Thank you