By Wayne A. Nishio, O.D.
This question has been the center of an ongoing debate for many years by vision scientists and eye doctors. Nearsightedness is also known by the scientific name myopia. Myopia is an optical or refractive defect of the eye that causes blur in the distance. Depending on the degree of nearsightedness, a nearsighted eye is able to see clearly at some point up close. That is why the term nearsighted is used.
Anatomically there are a number of variables that affect the refractive status, or focusing of the eye. The most significant measurable component of the eye responsible for nearsightedness is axial length. Axial length is the measurement of the eye from the front to back. This is done using sound waves. Nearsighted eyes have a significantly longer axial length than normal eyes.
A number of theories have been proposed trying to explain the causes of nearsightedness. At the heart of the question is a timeless argument: is nearsightedness a product of nature or nurture? Some scientists believe that the most significant factor contributing to the cause of myopia is heredity. Others believe that environmental and behavioral factors are more significant.
Studies to support both schools of thought have been published and scrutinized over the years. The number of possible contributing factors relating to myopia makes determining which theory (nature or nurture) is most important. Human studies are difficult due to different variables that cannot be controlled. Some factors may still be unknown. The best solution is to consider both as crucial components. In other words, heredity and environment are both significant.
As with any anomaly of the human body, heredity is something we have very little control over. We do not choose our parents or ancestors. What we can change is our environment and behavior.
Studies of identical twins confirm the link between genetics and myopia. Other population studies of school age children contribute to this theory. Some individuals are protected from developing nearsightedness due to genetics. On the other hand, there are a number of studies that support the other school of thought.
Reading and other "near point" activities are usually associated with theories that propound the environmental perspective. Studies have shown that certain populations have a higher proportion of nearsighted individuals genetically unrelated. For example, nearsightedness is much more prevalent in groups of individuals with higher education levels than less educated groups. Certain professions have a very high percentage of nearsighted individuals than the general population.
Such professions include lawyers, accountants, and computer programmers. Nearsighted conditions have been created in animal studies that center on the near point focusing theory. Population studies have shown that parents of first generation compulsory education children had significantly less nearsightedness than their children. These results show that the activities we engage in (especially in modern society) have the potential to change an otherwise healthy eye, regardless of genetics.
Nearsightedness is caused in part by the way we use our eyes. We know that nearsightedness tends to develop in certain age groups, but is not exclusive to any specific age.
If the environment does impact the incidence of myopia, what can we do to prevent it? Preventing nearsightedness should be addressed early in life. Encourage activities that require movement. Have your child explore their environment physically by crawling, walking, and running. The visual system is suited best for movement as opposed to sedentary activities. Hand held computer games and extended periods of desk activities should be discouraged. Limit the time spent watching television. Make sure your child is seated at least ten feet from the screen when they do watch television.
In families that exhibit a trait for myopia it may be advisable for children to use low powered plus lenses for all desk work and reading. Lenses of this nature reduce the demand on the visual system created by near centered tasks. Other effects on perception of space and visual processing are improved using these lenses. The overall effect is to allow the child to perform necessary near tasks without adversely affecting the eyes.
Behavioral changes will also add to the chances that the individual will not become nearsighted. Teach your child to sit tall when engaged in paper work, reading, and computer activities. Watch that he or she is seated in such a manner that their back stays in contact with the chair. This posture keeps the head high and away from the work surface. If writing or drawing, make sure that the hand grips the pencil in a manner that promotes good posture. When a pencil is held too closely to the writing tip the child may have to make postural shifts such as tilting and leaning forward to see where the tip of the pencil contacts the surface.
Limit the duration of each near centered work session. The maximum amount of time should be limited to fifteen or twenty minutes between breaks. Breaks should allow for physical movement that requires the visual system to shift to large space. Breaks should be long enough that the eyes feel relaxed and objects in the distance are clear.
If your child has already been diagnosed with myopia and glasses have been prescribed, similar recommendations are given to prevent the progression of nearsightedness. Depending on the degree of myopia, it may be advisable to remove the lenses for all near work. It is important to understand that lenses prescribed for the compensation of nearsightedness are in no way treating the condition. Some children are advised to wear their glasses at all times. Their parents tell them to "wear your glasses". This type of lens does not make the eyes better. Not wearing those lenses will not make the eyes worse. In fact it is advisable to limit the use of the lenses to activities that specifically require clear distance vision such as board work, certain sports, and overhead projectors.
In practice, some patients actually see a reduction in nearsightedness over time. The reason for improvement in vision is difficult to determine. Good visual habits will give you the best chance of maintaining good vision.
Consider how nearsightedness is treated once it becomes significant. Glasses or contact lenses may be required for the rest of your life. Refractive surgery may be done for the treatment of myopia as long as you meet the necessary criteria. Refractive surgery does not guarantee that the eye will not develop nearsighted vision again. There are treatments using rigid contact lenses in an attempt to mold the shape of the cornea. There is usually a reversion to myopia when you stop using the retaining lenses.
The next time you call your doctor for an appointment for an eye examination ask the office what they think about the question: Can nearsightedness be prevented or controlled? You will find that many doctors consider nearsightedness and its progression inevitable for many people. It is routinely treated with no discussion of cause or possible lifestyle management.
A preventive approach makes sense. The benefits far outweigh any possible risk. Most importantly, follow the advice relating to behavioral changes and nearsightedness. You can do that on your own.
As mentioned previously, the controversy over the cause of nearsightedness has existed for many years. We know that genetics is a significant factor. Behavior and environment are also important. We can control certain behaviors and our environment. Do what you can for your family as it will affect their vision for a lifetime.