1. VISUAL SYSTEM Key points
Relations of neural retina to other structures in the eye
Knowledge of types of photoreceptor and their distribution across the retina
Foveal versus peripheral retina
Knowledge of the different cell types that make up the retina
There are different types of retinal ganglion cell – thus parallel outputs from the retina and beyond….
Central visual pathways – projections to LGB and other subcortical visual structures
Organization of visual fields – partial decussation at optic chiasm, binocularity, topography
Projection to primary visual cortex – optic radiations
Effects of lesions on visual function
Reading
Nolte (4th Ed), pgs
Crossman and Neary, pgs
Fitzgerald, pgs ,
Kiernan (7th Ed), pgs
Pritchard and Alloway, pgs

3. The human eye

4. Mouse retinal wholemount
NB Retina and optic nerve are derived from the neural tube – are of CNS origin

5. Photoreceptors
rods cones

6. LIGHT

8. light
light

9. Cone photopigments
130 million rods – monochromatic – high sensitivity – convergence
7 million cones – colour – central retina – high acuity – photopic vision
1 million retinal ganglion cells per eye – efferent cell

10. Retinal circuitry light ONL OPL INL IPL GCL output signals
Photoreceptors
Horizontal cells
Bipolar cells
Amacrine cells
Ganglion cells
rod
cone
light
output signals

11. There are different classes of retinal ganglion cell:
On/off cells, large and small receptive fields, sustained versus transient responses, monochromatic versus colour……(etc!!)

13. Visual Pathways Retina (rods, cones, fovea) bipolars
ganglion cells - optic nerve
Chiasm (nasal fibres cross)
Optic tract
suprachiasmatic nuclei (diurnal rhythms)
pretectum (for eye movements)
superior colliculus (new objects, co-ordination of eye and head/neck movements)
lateral geniculate body of the thalamus (to cortex)

14. Visual fields and central visual pathways in the human

15. Lateral geniculate nucleus human monkey

16. Visual topography – maps

20. Control of Eye Movements
Medial longitudinal fasciculus connects all the cranial nerve nuclei (III, IV, VI) together
Descending cortical input
Input from superior colliculus
Input from ascending cervical proprioception
Optic Reflexes
Pupillary constriction (Edinger-Westphal)
due to light (consensual…both eyes at once)
On accommodation - convergence

23. Classes of RGC CAT MONKEY On/off cells sustained X/transient Y
not much colour
MONKEY
On/off
Parvo (P) colour (red/green) and form
Magno (M) motion

24. Ocular dominance stripes in layer IV
Monkey area 17 (V1)
Ocular dominance stripes in layer IV
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