Eye conditions relating to blindness

Legally blind people can be broken into two categories: those who are totally blind, and those who are vision impaired.

Many people think that blindness is seeing black. It is not. There are varying degrees of vision impairment.  Most people we call legally blind have some form of vision. Very few are completely blind. Completely blind people cannot see anything at all, and do not react to light. Sometimes, vision impaired people may see shapes, but perhaps not in detail. Others may have tunnel vision, while yet others have blurry overall vision. Each person will be different. If your eyesight is failing, you can be referred to your local Blind Foundation directly, or through your local GP, optometrist or opthalmologist. Please contact your local Blind Foundation for information on their referral process.

Visual impairments and blindness can be hereditary, caused by environmental factors or even from accidents. They occur in people of all ages, although a majority of people are generally elderly - due to age related issues. Some examples of causes of blindness and vision impairments may be: walking into objects that may penetrate the eye, rubbing your eyes when there are chemicals or other substances on your hands, losing sight through illnesses such as meningitis, and so on.
Remember, each person is different, and it is important to seek medical advice, rather than try to self diagnose any potential issues. Imagine how you would be affected if you had any of the eyesight conditions mentioned below. Below are some of the more common vision impairments, (along with a picture of normal vision to compare some of the other eyesight conditions view of that same picture to); and a brief description as to how they may affect vision:

Normal vision

This is a picture of a white guide dog with a brown harness, sitting on green grass
A person with normal vision might see the whole picture clearly.

Macular degeneration

Macular degeneration is predominent in people aged 55 and over. Some people may have a loss of their central vision (blurring, followed by distortion and eventually blind spots), and may only see around the outsides. Central vision loss from AMD occurs when photoreceptor cells in the macula degenerate. In most cases, if one eye has it, the other will develop it as well.

This is a picture of a white guide dog with a brown harness, sitting on green grass with a dark blotch in the centre of the picture.
A person with macular degeneration might see the outside of the picture but not the middle.

Glaucoma

People with glaucoma may have tunnel vision, and may not see things to the outside, as well as reduced night vision.

This is a picture of a white guide dog with a brown harness, sitting on green grass with only the centre of the picture visible
A person with glaucoma might see the middle of the picture but not the outsides.

Cataracts

Cataracts leave a cloudiness over the lens of the eye, causing blurred vision and sensitivity to glare. These can occur in either eye.

This is a picture of a white guide dog with a brown harness, sitting on green grass with the whole picture visible but clouded
A person with cataracts might see a cloudy picture.

Diabetic retinopathy

Damaged blood vessels in the eyes cause patchy vision, decreased night vision, and sensitivity to glare.

This is a picture of a white guide dog with a brown harness, sitting on green grass but the view is very patchy
A person with diabetic retinopathy might see some colour, however the picture may be quite patchy.

Retinitis Pigmentosa

Retinitis Pigmentosa (RP) refers to a group of inherited diseases that cause the retina to degenerate. The retina (which lines the back inside wall of the eye) is responsible for capturing images. People with RP experience a gradual decline in their vision because photoreceptor cells (rods and cones) die. Forms of RP and related diseases include: X-linked Choroideraemia, Usher syndrome, Leber’s congenital amaurosis, Rod-Cone disease, Bardet-Biedl syndrome, and Refsum disease, among others. Symptoms depend on whether rods or cones are initially involved. Rods generally, are affected first. The outer rods are triggered by dim light, and their degeneration affects peripheral (outside) vision and night vision. The more centrally located cones are responsible for colour and sharp central vision, and so affect colour perception and central vision. Night blindness is one of the earliest and most frequent symptoms. RP is generally diagnosed in teenagers and young adults. It is a progressive disorder which varies from person to person. Most people with RP are legally blind by 40, with a central visual field of less than 20 degrees in diameter.

In families with X-linked choroideraemia RP, males are more often affected, and females can be the carriers. (For example, a mother with three children may have two sons - one who is visually impaired and one who is sighted, while the daughter may or may not be a carrier). Choroideremia is a rare inherited disorder that causes progressive loss of vision due to degeneration of the choroid and retina. People with Usher Syndrome experience both RP (vision loss) as well as hearing loss and a loss of balance. Usher 1 is severe hearing loss and issues with balance at birth, and vision loss appears in early adolescence; Usher 2 is moderate to severe hearing loss at birth and vision loss appears after adolescence with hearing loss remaining stable; and Usher 3 is good or mild hearing impairment at birth, with vision loss appearing around puberty and balance may or may not be affected. People with Leber Congenital Amaurosis generally have severe loss of vision at birth.  Other related issues may include roving eye movements, deep-set eyes, and sensitivity to bright light.  Some patients with LCA also experience central nervous system abnormalities. Rod-Cone Dystrophy results from a primary loss of rod photoreceptors, followed by loss of cones. An initial loss of colour vision and of visual acuity is followed by night blindness and loss of peripheral visual fields. Bardet-Biedl syndrome is a complex disorder that affects many parts of the body including the retina. People with this syndrome will have an eyesight condition similar to retinitis pigmentosa (RP). They are born with extra toes and or fingers, and can suffer from obesity and may also suffer from developmental issues and kidney issues. People with Refsum disease generally have vision loss, the absence of the sense of smell, and a variety of other signs and symptoms. Some people with Refsum are born with bone abnormalities of the hands and feet, while others develop degenerative issues with other body parts.

Stargardt Disease

Stargardt disease is the most common form of inherited juvenile macular degeneration. Vision loss is progressive and caused by the death of photoreceptor cells in the central portion of the retina called the macula. Stargardt disease typically develops during childhood and adolescence. People with this may have decreased central vision, while still keeping their side vision. They may also notice a decrease in colour perception. This is because photoreceptor cells involved in color perception are concentrated in the macula.

Other not so commonly heard of eye conditions

Malattia Inessential

Small round white spots appear in the areas of the macula and optic disc, in early adult life. Progression to form a mosaic pattern termed 'honeycomb' occurs thereafter.

Blue-Cone Monochromacy

Blue cone monochromatism is characterized by poor central vision and colour discrimination, called partial complete colorblindness.

Retinoschisis

Juvenile retinoschisis is an inherited disease diagnosed in childhood that causes progressive loss of central and peripheral (side) vision due to degeneration of the retina.

Best Disease

Best disease, also known as vitelliform macular dystrophy, is an inherited form of macular degeneration characterized by a loss of central vision.

To find out more or to locate a support group

To find out more about different eye conditions and support groups that you can join, please go to the following link
NZ blindness, disability and support organisations websites

Please remember:
You only have one set of eyes and once they are damaged they can't be fixed.  While you are young please protect your eyes. Simple actions that you can take are things like: wearing your sunglasses, eating properly and not playing around with sharp objects. While not all vision impairments can be prevented, some certainly can, and some others can be minimised.
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