Understanding the most common types of vision loss
This section provides information about the most common eye conditions that cause blindness and low vision.
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Conditions on this page:
Aged related macular degeneration
Macular degeneration causes a loss of central vision, which affects such tasks as reading and recognising faces. Dry macular degeneration accounts for most cases and has no specific treatment, but the wet variant may be stabilised by intraocular injections. Vision Australia can advise on optical magnifiers and other devices so your patients can continue to access print and enjoy leisure activities. There are also now electronic magnifiers that use a camera to enlarge and enhance print. Some devices can also convert text to speech as well as enlarging it.
The following images give an impression of what someone with age-related macular degeneration may see compared to someone with regular vision.
Albinism is an inherited condition. It affects the eyes and skin of some individuals, and only the eyes of others. It results from the body's inability to produce normal amounts of a pigment called melanin. There are two types of albinism – ocular albinism and oculocutaneous albinism. Both can affect children’s vision. They may need some form of visual aid, depending on the type and extent of their visual condition. Glasses or contact lenses can correct for short or long sightedness or astigmatism. Older children may need a monocular for distance viewing and some may need large print or a magnifier for reading. All children with albinism benefit from sunglasses and hats to reduce glare.
A cataract is a clouding of the lens of the eye causing impaired visual acuity and glare. Cataracts are common in the elderly. Risk factors in-clude UV (sunlight) exposure, smoking and corticosteroid therapy. Sun protection and not smoking may prevent or delay cataracts. Intraocular lens implants can correct visual loss. Cataract surgery is safe and effective for most patients, although surgery may not be an option in some cases due to other ocular pathology or general health issues. The functional impact of cataracts varies considerably and may cause patients to lose contrast sensitivity and visual acuity, and have difficulties with night vision and sensitivity to glare.
Cataracts in infancy and childhood
While cataracts most commonly occur in those who are older, they can develop in younger people as well. Some people are born with a cataract.
Sometimes no single cause for cataracts can be identified. There may be a family history of cataracts. The other main causes are due to infection of the unborn baby in the womb, genetic conditions and some metabolic genetic conditions. The cataract can occur in only one eye or may be present in both.
When is surgery necessary for removal of the cataracts?
Congenital cataracts (present at birth) and developmental cataracts are the most common cause of surgically treatable blindness in infancy and childhood. The size of the cloudy area of the lens, the degree of density of the cataract and the position of the opacity in the lens will all be a factor in the determination of whether the child needs to have surgical removal of the cataract and how soon after birth the cataract should be removed.
Some cataracts are slow to progress and do not cause an interruption to normal patterns of visual development. These cataracts will be monitored carefully by an eye doctor and removed only if they are causing a significant visual impairment.
If the child is born with dense cataracts interfering with vision they will be removed within a few days of birth.
The following image gives an impression of what someone with cataracts may see.
What is Charles Bonnet Syndrome?
This syndrome is characterised by the presence of complex visual hallucinations seen by people who have vision loss. The hallucinations can involve detailed images of people, buildings or simple patterns of straight lines. This experience can be pleasant but can sometimes cause distress. People who have Charles Bonnet Syndrome are aware that these images are not real but they may worry that it is an early sign of mental illness. Charles Bonnet Syndrome can affect people of all ages who have significant vision loss. However it is more common in those who lose their sight later in life. The condition often appears after a period of worsening sight and is common in people with age-related macular degeneration. The visual hallucinations usually stop within a year to 18 months.
Cortical visual impairment
Cortical visual impairment is a temporary or permanent visual impair-ment caused by the disturbance of the visual cortex or posterior visual pathways of the brain. The degree of neurological impairment depends upon the time of onset and the location and intensity of the damage. The eyes may function normally but the visual systems of the brain do not consistently understand or interpret what the eyes see. Certain characteristics are common to children with cortical visual impairment. A significant characteristic is fluctuation in visual functioning. That is, the child may be more visually aware on one day or in one hour than the next. This often coincides with fluctuations in level of attention.
Another is that children with cortical visual impairment may appear to look at an object of interest and then look away from it when reaching for it.
Children with cortical visual impairment often perform better visually when activities have minimal clutter and external distractions such as noise, are eliminated. They may also benefit from prior instruction of what to look for. Visual activities are performed better by the child if they contain simple, constant and predictable information. The child may benefit by complementing their visual input with something that they can feel.
Leber’s congenital amaurosis
An inherited condition which is present from birth. The extent of vision loss varies, but it can be quite severe and a baby may be born with very poor vision or may even be totally blind. Children born with Leber’s congenital amaurosis have poor vision because of the impaired development of the retina, which is the light sensitive film at the back of the eye. The retina contains receptors called rods and cones, and these receptors respond to light.
The cones are designed to function in high levels of light and give us our central, detailed vision. The rods are designed to function in lower levels of light and give us our peripheral (side) vision. If they are working properly, receptors will send a message back to the brain about the picture that is being seen. If they are not working properly, very few or no messages are transferred to the brain, so very little or nothing is seen.
All diabetics are at risk of retinopathy, which can progress to blindness. Early detection of diabetes and retinopathy are therefore critical. Regular eye examinations along with effective control of diabetes, blood pressure and cholesterol levels can prevent or delay the development of permanent visual loss.
Adaptive technology can be an essential tool for patients who want to retain employment and general independence. Orientation and mobility can also be vital for them to develop independent travel skills. Advice on lighting and magnification can also help with reading and other daily activities.
The following images give an impression of what someone with diabetic retinopathy may see compared to someone with normal vision.
Glaucoma is a common cause of visual impairment and is induced by raised intraocular pressure. It usually presents with loss of peripheral and low light vision, which can result in late diagnosis.
Regular eye checks from an ophthalmologist or optometrist are important, particularly for people at risk because early diagnosis and treatment usually prevents visual loss or blindness. It can often reduce people’s ability to drive, so orientation and mobility services can help them regain some independence. Daily living skills and reading may also be affected and respond to advice from occupational therapists and orthoptists.
The following images give an impression of what someone with glaucoma may see compared to someone with regular vision.
This condition includes a number of genetic disorders affecting the peripheral retinal rod cells causing progressively worsening night blindness and tunnel vision. There is currently no curative or preventative treatment. It commonly affects people from a young age so patients may need support during school and to get or retain jobs. Vision Australia provides a range of support for children of all ages as well as employment services for working-age adults with vision loss. Orientation and mobility services and adaptive technology may also help patients with retinitis pigmentosa maintain their independence.
The following images give an impression of what someone with retinitis pigmentosa may see compared to someone with regular vision.
Keratoconus is an eye condition that causes the cornea to thin and bulge forward. This affects the way light hits the retina, causing distorted vision. It usually occurs in adolescence, or shortly after, and in most cases will stabilise by the age of 35. Some evidence suggests that keratoconus is a genetic condition and can be passed to a child if both parents carry the recessive gene. However, most cases show no definite pattern. Symptoms begin slowly and can be hard to detect but include distorted or blurred vision, and sensitivity to light and glare. Keratoconus cannot be treated with drugs, although glasses and contact lenses can help.
The following images give an impression of what someone with keratoconus may see compared to someone with regular vision.
Nystagmus refers to rapid involuntary movements. It is caused by an abnormal central control of eye movements. Nystagmus may be present at birth or develop later in life. Symptoms include blurred vision (because the eyes are always moving) and abnormal head posture (some people find that their eye movements reduce in certain positions).
The following images give an impression of what someone with nystagmus may see compared to someone with normal vision.
Optic atrophy is the result of degeneration or damage to the optic nerve. It may be inherited or result from brain injury or conditions such as brain trauma, inflammation, degenerative disorders, haemorrhage or tumour. It can be progressive or static depending on the cause of the damage.
Examination by an eye health professional may show a pale optic disc. Vision loss will vary depending on the severity of the atrophy. Optic atrophy cannot be treated although in some circumstances the cause of the damage may be treatable.
Optic atrophy no barrier to a full life: Troy and Rebecca share their stories.
Stargardt's disease is a form of macular degeneration that typically manifests before the age of 20. It causes a progressive loss of central vision of both eyes. Symptoms may include blurred vision, deterioration of central vision, a central blind spot, diminishing ability to perceive colours, and difficulty adapting from bright sunlight to a dimmer room. It is usually an inherited, autosomal recessive with both parents carrying a defective gene. There is no known cure for Stargardt's.
The following images give an impression of what someone with Star-gardt’s disease may see compared to someone with normal vision.
The cause of the stroke and area of the brain affected will determine the type of vision impairment. Stroke can affect visual field (resulting in loss of side or peripheral vision), visual perception (resulting in impaired spatial awareness), visual acuity (resulting in blurred vision) and eye muscles (resulting in double vision).
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