Unit 6: Differential Diagnosis of Blurred Vision

Characteristic features:

• Raised IOP
• Cupped optic nerve head [Glaucomatous disc cupping]
• Progressive visual field defects
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  Progressive visual field defects

  

  The black areas show the parts of the visual field not seen during automated visual field testing. Note the central area (centre of crosshairs) is still preserved, despite extensive loss of peripheral vision. Over time (top to bottom) the visual field defect increases.

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Glaucomatous disc cupping

In glaucoma raised IOP damages nerve fibres. As they die away the neuro retinal rim gets thinner and therefore the cup gets larger.

Source: retinagallery.com

Optic disc assessment

The normal optic disc has a neuro retinal rim comprised of the retinal nerve fibres, which are exiting the eye down the optic nerve.

The centre of the disc does not have fibres and is termed the optic disc cup.

Healthy optic nerve

In healthy eyes the cup-to-disc ratio is typically 0.2 or 0.3. A ratio greater than 0.6 is suspicious.