Blindness
From IKE
Contents |
Ocular causes
Definition
Blind
- Inability to count fingers at a distance of 3m or less
- ≤ 3/60 in both eyes
- OR restrictions of the visual field
Partially sighted
- Inability to count fingers at a distance of 6m or less
- ≤ 6/60 in both eyes
Prevalence
- Less than 20% of legally blind people are totally blind
- Most of these can distinguish light from dark
- 70% of people with visual disability are >75 y.o.
- 8% of people with visual disability are born with the disability
- 60% of people with visual disability due to other serious illness
- 25% of people with visual disability are employed
Dysfunction
Cornea
- Oedema - injury / degeneration of corneal endothelium
- Stromal scar - chemical / physical / infectious agent causing fibroblastic proliferation, irregular deposition of collagen, and neovascularization
Aqueous outflow pathway
- increased resistance to outflow and raised intraocular pressure (IOP)
- see glaucoma
Lens
Retina
- detachment
- rhegmatogenous - tear in the neurosensory retina that allows vitreous fluid to seep beneath the retina
- exudative - fluid or abnormal tissue accumulates beneath the intact neurosensory retina
- tractional - fibrous or fibrovascular tissue within the vitreous pulls the neurosensory retina away from the retinal pigment epithelium
- retinoblastoma in children
- pre-retinal neovascularization (as in diabetes)
- hereditary degeneration (retinitis pigmentosa)
- subretinal neovascularization and scarring (as with age-related macular degeneration)
Choroid
- site of most intraocular tumours in adults (primary or metastases)
Optic nerve
- papilloedema
- optic neuritis
- tumours
