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Vision Notes

This is a sample of our (approximately) 7 page long Vision notes, which we sell as part of the Neurology Notes collection, a 70-80% package written at Bristol University in 2012 that contains (approximately) 117 pages of notes across 36 different documents.

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Vision Revision

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Lecture 31, 32 & 34 Vision 1

Properties of light o Visible light is what we see o Visible light=400-700nm (wavelength) o In vacuum, light travels in straight line, most of what we see is reflected and scattered from objects Structure of the eye o Extrinsic ocular (Extraocular) muscles
 Superior rectus (upwards; into nose)= CNIII
 Inferior rectus (down)= CNIII
 Lateral rectus (away from nose)= CNVI
 Medial rectus (into nose)= CNIII
 Superior oblique (torsion of eye; down, in, out)= CNIV
 Inferior oblique (torsion; keep gaze stable)= CNIII o Pupil= allows light to enter eye (controlled by size of iris o Iris (sphincter pupillae)= Muscles that control size of pupil
 Radial=dilate; Circular=constrict o Lens= curvature controlled by ciliary muscle (PSNS fibres via ciliary ganglion) o Aqueous humour= Between anterior and posterior chamber
 Feeds lens and cornea (no BVs)
 Replaced every 60 mins
 Excess production=glaucoma (carbonic anhydrase inhibitors) o Vitreous humour o Choroid layer= Vascular layer of eye containing connective tissue. Between retina & sclera
 Dark melanin choroid pigment helps limit uncontrolled reflection of light (clearer vision)
 In night animals, melanin partially absent (Tapetum lucidum) collects light reflecting it in controlled manner. Maximises light capture BUT less visual acuity o Retinal landmarks
 Optic disk/Optic papilla (blind spot)

• Axons of ganglion cells exit and enter optic nerve
 Macula (yellow disk)

• Central area of retina in line with visual axis
 Fovea

• Depression in centre of macula

• Visual acuity greatest here

• Slightly darker because light passes through easily

• Extremely thin- cells in front of photoreceptors swept aside

• No rods in fovea, only cones
 MACULA DEGENERATION (2 types: wet or dry)

RETINITIS PIGMENTOSA (night vision and peripheral vision loss)

Image formation in the eye o

Pupils and papillary light reflex

Change amount of light in eye

Dilated o o

Light spread over large area

o

Lots of light

Low visual acuity

Contricted o o

o

Light beams more focused Higher visual acuity

Pupillary light reflex

Lens

Transparent biconvex structure behind iris

Considerably flexible (deteriorates with age- PRESBYOPIA)

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