Visual impairments - effect on visual fields and daily life
- Early stages of cataract, glaucoma, retinitis pigmentosa, macular degeneration, macular degeneration, diabetic retinopathy
- Homonymous hemianopia
- Optic Neuritis
- Bitemporal hemianopia
- Central field visual loss
- Moderate peripheral vision field loss
- Lower vision field loss
- Patchy vision loss
- Nerve pathways and damage
Early stages of cataract, glaucoma, retinitis pigmentosa, macular degeneration, macular degeneration, diabetic retinopathy.
In conditions such as early cataract and glaucoma, early retinitis pigmentosa, mild macular degeneration, and mild diabetic retinopathy, the effect on vision is slight, and should not affect daily life.
In early retinitis pigmentosa, and glaucoma, there may be a small loss of peripheral field, so the affected person would have to be extra vigilant with outdoor steps and kerbs but both conditions may progress.
Homonymous hemianopia
In a condition called homonymous hemianopia the optic nerve pathway is damaged in the brain, and the same half of the visual field of each eye is affected. (For example, if the damage occurs to the right side of the brain, because of a stroke or tumour, say, both eyes lose the left half of their visual field.) This causes a considerable disability because the result is that the patient ignores the left side of their body, or the left part of a book, for instance. These people will constantly need to be reminded to remember the left part of the body in washing, dressing, and pouring drinks etc., they will have problems reading and writing, and are likely to ignore the left part of their environment, without prompting. This is extremely relevant as they tend to bump into things, and not see obstacles on the affected side, they are likely to have problems when using stairs, and getting about, out of doors, crossing roads, and negotiating kerbs for example.
Optic Neuritis
If damage to one optic nerve occurs, as in optic neuritis, a central visual field loss will occur in one eye only.
Bitemporal hemianopia
If damage occurs further back in the brain where the fibres from the optic nerves cross over, in the optic chiasma, a bitemporal hemianopia will result, that is, the outer half of the field of vision is missing in each eye.
Central Field visual loss
With central field of vision loss (as in macular degeneration, and optic neuritis), and hazy vision, such as in glaucoma and cataracts, people will have trouble with things like fine print, and will not be able to see fine detail. They will not be able to see normal print, labels, instructions, bills and recipes, for example. When out and about, they may have difficulty reading signage, and will have problems recognising people.
Glare from natural or artificial light can be a big problem for people with cataracts, retinitis pigmentosa and glaucoma. Specially tinted or Polaroid glasses can help to some extent.
Moderate Peripheral vision field loss
With moderate peripheral vision field loss, as in retinitis pigmentosa, glaucoma, and bitemporal hemianopia, extra vigilance, and indeed assistance will be needed on stairs, and out of doors, to negotiate kerbs and pavement irregularities. However, as the central field is unaffected, they will have no problem reading signs, and recognizing landmarks. Until acclimatised they may bump into others when walking.
Lower vision field loss
If mainly the lower field of vision is affected, as in damage to part of the brain called the parietal lobe, the affected person would normally have problems getting about, as they are not able to see their feet, the ground, steps, and obstacles.
Patchy vision loss
People with patchy vision loss, as in diabetes, and those susceptible to glare, as in cataracts, Retinitis Pigmentosa, glaucoma and macular degeneration, may also not be able to manage steps and obstacles without assistance. These people are likely to have difficulty making out fine detail, and the printed word (depending upon the extent of the vision loss.)
However, for a person with central visual field loss, such as in MD, small obstacles on steps will pose a problem, though retaining the peripheral field will help to some extent, as will the person’s familiarity with steps in their own home. Steps out of doors, which are unfamiliar will also cause problems, to some extent.
Diagram of nerve pathways from eyes to brain and results of damage
Nerve pathways from eyes to brain and results of damage
(How Vision is affected)
1. Damage at site of one Optic Nerve
2. Damage at Site of Optic Chiasma (where some fibres cross over), for example, from a pituitary tumour
3. Damage further back in Optic Nerve pathway (often as a result of a stroke or tumour).
For simulations of visual impairments click on the web site below and then click on ‘Site map’ on the top menu followed by ‘Other vision impairments’
