Age-related changes in vision starts around the age of 40 years. It is usually minor in the early stages but gets progressively worse over time. This age-related change in vision is known as presbyopia. It must not be mistaken with the other vision problems in life such as myopia (short sight), hyperopia (far sight) or astigmatism. Sometimes these pre-existing vision problems from earlier in life complicates presbyopia in the senior years. However, all of these vision problems can be corrected with eyeglasses.
These types of vision problems are known as refractive errors. Light is bent by the cornea and lens of the eye to focus a shape image and the light-sensitive area at the back of the eye. This allows for visual acuity, meaning that a person is able to see a sharp image. The ability of the cornea to bend light, known as the refractive index, does not change in life. The final focusing of the incoming light needs to be corrected by the lens of the eye which is flexible.
The lens of the eye, which has a smaller refractive index, changes at will. Long strands that hold up the lens in the eye can shorten or length almost instantly. This causes the lens to become thinner or fatter thereby altering the degree to which light is bent. It allows for humans to see objects nearby as well as a distance and is known as accommodation. With age, however, the lens becomes stiff and cannot change shape and therefore bend light as easily.
One of the common types of corrective measures for seniors is the use of bifocals eyeglasses. It uses two types of lens – one for reading and near vision and another for distant vision correction. The types of lens depends on the needs of the patient, although commonly used variations are available over-the-counter at pharmacies and supermarkets.
There are similar variations to the bifocals concept known as trifocals and multifocals. These types of eyeglasses incorporate three or more lenses to correct more than one vision problem. There is usually a clear distinction between the lenses and a person will look through one type of lens or the other as is needed for the viewing distance. Multifocals especially are very useful for the elderly who naturally lose the ability to focus on different distances instantly.
A more popular option these days are progressive lenses. This type of lens have different areas for distant, intermediate and near vision with a gradual transition between these zones. It does not have the clearly discernible lines that separates one type of lens from another as with bifocals, trifocals or standard multifocals. This is a cosmetic advantage for the more conscious wearer. Therefore progressive lens are also known as no-line bifocals. Furthermore, the gradual transition between zones in progressive lenses means a wider range of corrective options.
Choosing the right lenses are dependent on a number of factors such as :
It is therefore advisable that seniors consult with an optician and opthamologist (eye specialist) to determine the type of lenses that best suit them. Buying bifocals over-the-counter may be a convenient measure for a short period of time but if it is not suited to the person it can cause eyestrain and headaches. Furthermore seniors need to be examined as there are a host of other eye problems that can affect vision and cannot be corrected with eyeglasses.