Understanding When Spectacles Help
Spectacles (eyeglasses) are the most commonly prescribed prosthetic device in the United States. Essentially all people could enjoy improved vision with spectacles at some point in their lives, but not all people will get them at the same time for the same reason. Ophthalmologists are physicians who have taken extensive post-graduate training in the diagnosis and management of all eye problems. They will work with patients to help them achieve the best vision they could possibly have, and in most cases, will use spectacles to achieve this result. In some cases, if the patient so desires, the ophthalmologist will prescribe contact lenses or refractive surgery. These topics are discussed under other sections.
Myopia
The job of the focusing mechanism of the eye is to bring light rays to a point, the focal point, and to place this focal point on the area of most sensitive vision at the back wall of the eye, the fovea. The fovea is a small area within the neural tissue of the eye known as the retina; it receives the focused light rays, converts the light into chemical signals, and ultimately sends this information to the brain. When the focusing mechanism of the eye is too powerful relative to the length of the eyeball, the image is brought to a focal point too far forward, in front of the retina, so that the retina receives an unfocused image. The retina cannot clarify this image and so the brain receives information pertaining to a blurred image. This condition is called myopia, or near-sightedness. Myopic patients soon find that if they bring an object closer, they will see it more clearly. This is partly because objects appear larger as they are brought closer (i.e., they become magnified), but more importantly, because the image of an object moving closer to the retina will also be moved closer to the retina, correcting for the overly powerful lens system. Hence, these patients see better with near objects. Myopes need spectacles to see better at distance, and will enjoy driving, strolling, and stargazing much more when corrected. On the other hand, they will probably not require reading glasses until much later, if ever, in life.
Hypermetropia
Hypermetropes, or far-sighted individuals have a lens system that is relatively too weak, and their eyeball acts as if it were too short. Fortunately for them, they are able to pump in lens power with their natural lens (a process called accommodation) and supply the requisite power needed for seeing at a distance. However, they may find it tiring or even impossible to work at close tasks such as reading, sewing or tying flies, since they are already working just to see at distance and have only limited extra lens power to see at near. These patients will often get along without glasses until they reach their adult years (later 30's to early 40's) when they find they cannot read without holding objects far from their face.
Astigmatism
Most of the focusing (or refractive) power of the eye comes not from the lens but from the cornea, the clear window of the eye. If the cornea is not a smooth round surface, but instead more curved in one plane and less in another (resembling a football rather than a basketball), it will not focus light uniformly. It is like having nearsightedness and farsightedness at the same time, except there is no distance that an object might be positioned so that it could be seen clearly! Patients with astigmatism often squint, because this causes the eyelids to create a slit-like opening that removes many of the unfocused rays. Unfortunately, this also reduces light gathering ability and causes eyestrain, so that it cannot be maintained for a long time. For the same reason, these patients will often look at you out of the corner of their eye by turning their heads. If undiagnosed, astigmatism may prevent a child's brain from ever receiving a clear image and that brain will not develop its visual centers correctly. This condition, called amblyopia, is essentially irreversible after age 9 years. Astigmatism is correctable with spectacles in most cases, and patients need to be given their full correction. However, if a patient has never worn astigmatic lenses, they may take some time getting adjusted; in some patients, spectacle power may requiring incremental changes until the full correction or best vision is achieved.
Presbyopia
As we age, our ability to pump focusing power into our natural lenses (i.e., accommodate) is decreased. The inability to accommodate restricts the wide range of distances over which we once enjoyed good vision. In fact, close work becomes especially difficult because that is where accommodative power is needed most. The accommodation deficiency associated with aging is called presbyopia and is usually noticeable by age 40 years. Myopic patients often compensate for this problem by removing their distance glasses and taking advantage of their natural nearsightedness. Hypermetropic patients will often move their reading material further away, although this tends to make everything smaller and tougher to read. Eventually, they will go to their eye doctor complaining that their arms are just too short to read anymore, and will learn that simple reading glasses will usually be effective. If a patient wears spectacles all the time and does not want to remove them (a busy myopic or astigmatic patient), he does not have to buy a separate pair of reading glasses. Instead, a reading "add" can be ground into his spectacles, thereby creating a bifocal, a lens with a built-in secondary prescription. Although this is certainly a benefit, bifocals take some time for adjustment as patients soon learn that images become displaced or jump when they look from one lens to the other. This can be particularly disturbing when one is walking down stairs or off a street curb.
Sports, Work, and Spectacles
Many activities pose risks to the eye. Any sport involving projectiles can and has been associated with serious eye injuries. Any occupation in which something might become airborne is also fraught with danger to the eyes. Eye protection is an absolute necessity for many undertakings and most specialized eye protective equipment can be made with the wearer's own prescription built in. Swim goggles, scuba masks, laboratory goggles, shooting glasses and mountaineering goggles are just a few of the applications where corrections can be built into the protective device. Whatever your hobby or occupation, please assess possible risks to your eyes and take measures to protect them. At Eye Doctors of Lancaster, we are happy to perform on-site evaluations of your work or play environment to help advise you as to what eyewear would be preferable.
When Spectacles Do Not Help
Sometimes spectacles are not the answer to a patient's vision problems. For some people, spectacles do not provide the clearest or the most useable image. This is often the case in patients with strong prescriptions, where spectacles tend to magnify or minify objects. This may also be the case in patients with a significant degree of astigmatism. In addition, some patients work in occupations where glasses become a nuisance or even hazardous, especially where the spectacles might become fogged, lost or easily broken. Although glasses are now made in many attractive shapes and lightweight materials, some people just cannot tolerate them on their face. Spectacles also would be of little help if the eye itself is not healthy. Disease of virtually any part of the eye will reduce vision. Patients often do not understand why their glasses are insufficient and will go from glasses store to glasses store getting new glasses with no satisfaction until they are given the explanation that glasses can only help make healthy eyes see normally. At Eye Doctors of Lancaster, we are committed to diagnosing and treating problems associated with eye diseases so that our patients have healthy eyes.
