Part 1

• What do we need to be able to see?

  Clear cornea

  Clear lens

  Retina

  Optic nerve
• 40% of the brain is involved in visual processing.
• What does the cornea do?

  Light refraction
• What does the lens do?

  Focusing
• What does the iris do?

  Controls the size of the pupil and regulates the amount of light entering the eye.
• What does the retina do?

  Phototransduction

  Light transformed into electrical signals
• What does the optic nerve do?

  Transmits electrical signals to the brain
• What are the layers of the cornea?

  Epithelium - smooth optical surface for refraction, barrier to water & bacterial entering the cornea - constantly replaced

  Bowman's layer

  Stroma (keratocytes)

  Descemet's membrane

  Endothelium - single layer of hexagonal cells, allows transport of nutrients (glucose into cornea), pumps water out to maintain clarity of stroma - never replaced
• What is emmetropia?

  Normal vision
• What is hypermetropia?

  Long-sighted

  Corrected with convex lens

  
• What is myopia?

  Short-sighted

  Corrected with concave lens

  
• What is astigmatism?

  An eye condition that causes blurred vision due to an irregularly shaped cornea or lens.

  Corrected with 'cylindrical' lens is used with different pwers in the different axes
• What is shown in the image?

  Corneal ulcer

  Can be complication of poor hygiene with contact lens wearers

  
• What is the role of the lens?

  Some refraction, accommodation & fine focus

  -> circumferential ciliary muscle contracts & relaxes to alter tension of lens capsule allowing lens to change shape
• What is catarct?

  Clouding of the lens
• What can cataracts be caused by?

  Age

  Diabetes

  Corticosteroids

  Congenital

  Trauma
• Fill in the blanks

  A) Epithelial cells

  B) Anterior capsule

  C) ciliary muscle

  D) Corticl fibres

  E) Posterior capsule

  F) Nucleus

  
• What is shown in this image?

  Cataract

  
• Fill in the blanks (layers of the retina)

  A) Choroid

  B) Retinal pigment epithelium

  C) Photoreceptors

  D) Bipolar cells

  E) Ganglion cells

  F) Nerve fibre layer

  
• What is the fovea?

  The central part of the retina responsible for sharp central vision.
• What is present at the fovea, in terms of rods & cones?

  No rods

  All cones

  
• What is CRAO?

  Central Retinal Artery Occlusion

  Retinal loses blood supply -> retina thins as cells die -> vision is poor
• What is shown in the image?

  Central Retinal Artery Occlusion

  
• What is shown in the image?

  Central Retinal Vein Occlusion

  
• What occurs in central retinal vein occlusion?

  Venous thrombosis -> haemorrhage, oedema, cottom wool sports & neovascularisation
• What is shown in the image?

  Diabetic retinopathy

  
• What occurs in diabetic retinopathy?

  Microvascular leakage & occlusion -> oedema, exudation & haemorrhage in inner retinal layers

  Ischaemia -> neovascularisation
• What is dry age-related macular degeneration?

  Build up of waste products from photo-transduction

  May lead to atrophic changes

  
• What is shown in the image?

  Dry age-related macular degeneration

  
• What is wet age-related macular degeneration?

  Inflammation & hypoxia -> choroidal neovascularisation -> breaks through into outer retinal layers -> oedema & haemorrhage -> causes distorted vision as photoreceptors are displaced

  
• What is shown in the image?

  Wet Age-Related Macular Degeneration

  
• Why do you get distortion with wet ARMD?

  Each cone is responsible for seeing 1 part of the face & that is mapped exactly in the occipital cortex -> oedema separate the cones their pixels will be different -> brain assembles image as though cones are in the correct place -> image is disorted
• What is the process of retinal detachment?

  Posterior vitreous detachment (PVD) -> PVD extends but vitreous remains attached to retina -> creates a tear in retina -> fluid can then track behind the retina -> fluid continues to leak behind the retina & with aid of gravity -> retinal detachment

  
• What is shown in the image?

  Retinal detachment

  
• What is shown in the image?

  Corneal dystrophy

  
• What is shown in the image?

  Coreneal oedema

  
• What is shown in the image?

  Corneal graft

  
• What is corneal dystrophy?

  Born with it

  Keratinocytes are not formed properly

  No discomfort

  Obstructs vision

  
• What is keratoconus?

  Most common dystrophy

  Cornea droops

  Treatment = vitamin B6 soak then UV light

  
• What is corneal oedema?

  Due to loss of endothelial cells