Questions about the usefulness of glasses for people with low vision are common, especially when the person is a young child.
- If the glasses are tinted, is the person wearing them in order to signal the public that they are blind?
- Shouldn’t the glasses correct the visual problem? Is the person lying about their visual difficulty?
- If the glasses cannot give the person normal sight, then are they of use at all?
- Is it really possible for an infant or toddler to benefit from glasses?
Glasses can be very helpful for a person who has extremely limited vision. This is because in addition to the condition causing the visual impairment, the person may also have a refractive error. The person who has additional damage to the eye will not experience complete correction while wearing the lenses, but correcting the error will allow the person to make the best possible use of their vision.
The images a person sees are made up of patterns of light which pass through several structures in the eye and brain before reaching the visual cortex, where they are interpreted as colors and recognizable images. The structures of the eye cause the waves of light to be bent in a certain way so that they are focused directly on the retina. This process is called refraction.
If any of the structures in the eye are damaged, abnormally shaped or have been removed, the light will not bend correctly. Images will be focused in front of or behind the retina rather than directly on it. This is called refractive error. A person with a refractive error will be able to see some things more clearly than others. Whether he sees nearby or far away objects better depends on the type of refractive error he has.
Refractive errors can be corrected with glasses or contact lenses. In some cases, a person can have surgery to correct the refractive error by changing the shape of the cornea. This is called refractive surgery.
When a refractive error has been corrected and the person has no additional eye problems, the person will have fairly normal vision. However, if the person has a condition which causes damage to the structures of the eye or part of the brain which is involved in seeing, vision may still be poor. Damage to the eye structures may cause an image to be distorted or keep a person from seeing many things at one time. This is why corrective lenses cannot always make a person see normally.
Correcting refractive errors is important for people with visual impairments because it enables them to maximize the use of the vision they have and to see things as accurately as possible. Additional features added to the corrective lenses, such as colored filters, may enable the person to see more clearly by enhancing contrast.
Every lens has a plus or minus number. The number represents only the strength of the lens and does not indicate how well the person will be able to see while wearing the lens. Plus lenses make objects appear bigger and are often worn by people who have had their natural lenses removed due to cataracts. Minus lenses may cause images to appear smaller. Because of this effect, some people who already have difficulty seeing small objects because of other eye conditions may prefer not to wear their lenses while doing certain things.
Glasses can be prescribed for very young children, including infants. If a young child is prescribed glasses, it is important to keep the glasses on to encourage visual development. The glasses prescription will likely change as the child goes older.
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