Farsightedness
(Hyperopia · Presbyopia)
In this condition factsheet:
The Facts on Farsightedness
Farsightedness, known medically as hyperopia, refers to being able to see fairly well at a distance but not close up.
Causes of Farsightedness
The cornea is the clear front layer on the surface of the eye that does most of the work of bending light as it enters the eye. Light must be bent properly so that it creates a sharp image. When parallel light rays pass through the cornea, they should be bent just enough to meet and focus on the retina (the light-sensitive membrane that lines the back of the eye). The lens is responsible for fine adjustments of focus.
In farsightedness, the light rays meet at a point behind the retina. This causes nearby objects to be blurred. It could be said that the eye is too short back to front, or alternatively that the cornea is too flat.
Farsightedness is at least partly genetic. Many children are born with a degree of farsightedness, but some are able to counteract it with strong eye muscles. These muscles squeeze and stretch the lens just behind the cornea, which fine tunes the focus after the cornea does most of the work of bending light. In some children, the close vision becomes naturally sharper by the age of 6. As people get older, their eye muscles become less able to change the lens shape in order to see close things clearly.
Around the age of 40, some people start to have some difficulty seeing close-up details clearly. This is called presbyopia. As you continue to age it becomes increasingly common. The lens becomes thicker and more rigid, and the range of distances at which you can focus (called accommodation) narrows.
Symptoms and Complications of Farsightedness
The main symptoms of farsightedness are difficulty seeing near objects clearly, headaches, and eyestrain.
You might think that farsightedness would be obvious to an adult. If your morning newspaper is getting increasingly blurred, you're likely to notice. In reality, the process is sometimes just too slow for the brain to detect. Farsightedness in children also often goes unnoticed. Some children born with farsightedness have never seen close objects clearly and may not be aware that it's possible to see them better. Also, hyperopic children can sometimes see close objects clearly by unconsciously straining their eyes. In such children, the symptoms of hyperopia may be headaches and frequently rubbing the eyes, not blurring.
In some children, research has linked farsightedness and poor reading and school performance. Children who may appear to lack an interest in reading quite often turn out to be slightly farsighted.
Many older people with farsightedness have a great deal of difficulty reading. Fortunately, farsightedness doesn't usually interfere with your ability to drive a car.
