Refractive errors and visual field defects Flashcards
Emmetropia
No refractive errors
Myopia
Short sightedness
Vision is better for near than for further away
Myopia - positive/negative lens
Negative lens
Myopia - concave/convex lens
Concave lens
Myopia - relationship with the retina
Visual images come in to focus in front of the retina
- images focus too early
Myopia - converges/diverges light?
Diverges
Hypermetropia
Long sightedness
Vision is better for further away than near objects
Hypermetropia - positive/negative lens
Positive lens
Hypermetropia - concave/convex lens
Convex lens
Hypermetropia - relationship with the retina
Visual images come into focus behind the retina
- images focus too late
Hypermetropia - converges/diverges light
Converges
Presbyopia - definition
Power loss due to age
Presbyopia - positive/negative lens
Positive lens
Presbyopia - concave/convex lens
Convex lens
Accomodative esotropia
Patient with hypermetropia with a manifest squint in which the eye is turned in
Astigmatism - definition
Eye does not focus evenly on the retina
Eye has 2 surfaces to correct
There is shape correction needed
Astigmatism - clinical features
Constant blurred vision at all distances
Diplopia
Double vision
Horizontal diplopia
Images are side by side
Problem with LR or MR
Vertical diplopia
Images are one on top of the other
Problem with SO, SR, IR, IO
Esotropia - definition
Inward squint, convergent squint
Esotropia - what movement do you see when covering good eye
Outward movement
Exotropia - definition
Outward squint, divergent squint
Exotropia - what movement do you see when covering good eye
Inward movement
Hypertropia - definition
High eye
Hypertropia - what do you see when covering good eye
Downward movement
Hypotropia - definition
Low eye
Hypotropia - what do you see when covering good eye
Upward movement
Visual field pathway
Optic nerve -> Optic chiasm -> Optic tracts -> Optic radiations -> Occipital cortex
Visual field defect
A lesion anywhere along the visual field pathway which results in a visual field defect
Optic nerve defect - cause
Ischaemic optic neuropathy
Optic neuritis
Tumours
Optic chiasm defect - cause
Pituitary tumour
Optic tracts and optic radiation defect - cause
Tumours
Demyelination
Occipital cortex - cause
Vascular disease (CVA) Demyelination
Optic nerve problem - patients vision
Can’t see at all in the affected eye
Optic chiasm problem - patients vision
Loss of temporal vision in both eyes (as temporal vision hits nasal retina and this crosses at optic chiasma)
Optic tract / optic radiation problem - patients vision
Visual field loss on the same side of both eyes (e.g. temporal vision lost on right eye, nasal vision lost on left eye)
Occipital cortex problem - patients vision
Visual field loss on the same side of both eyes (e.g. temporal vision lost on right eye, nasal vision lost on left eye) but macula is not affected
Sudden vision loss - causes
Vascular aetiology - CRAO - CRVO Vitreous haemorrhage Retinal detachment Wet ARMD Closed angle glaucoma
Gradual visual loss - causes
Cataract Dry ARMD Refractive error Open angle glaucoma Diabetic retinopathy
