The article will figure out who needs to wear glasses and why.
Most often, the question of the correct choice of glasses for vision correction arises in middle age patients. It is due to the development over time of age presbyopia (farsightedness). However, children and young people suffering from myopia (myopia), astigmatism and hyperopia (hyperopia) also have a similar need.
With all these pathologies, you need to wear glasses.
Eye examination, norm and pathology
The examination by an ophthalmologist is painless, simple and quick; it does not require any preliminary preparation from a person. Arriving at the reception, it is necessary to talk about eye problems and answer the doctor’s questions. The first stage of the examination is refractometry, which is done through a special apparatus. The man is conveniently located behind him, calmly looking straight ahead. Using an autorefractometer, the refractive power (refraction) of the patient’s eye is established, information is obtained on the degree of astigmatism, that is, defects in the clarity of vision, as well as differences in eye refractions. This study is very accurate, fast and completely painless for humans. An ophthalmologist receives information about the degree of myopia or hyperopia in a patient, measured in diopters - special units.
The next stage is an external examination of the organs of vision under a microscope. Thanks to him, the state of the cornea, the presence or absence of inflammation is determined.
To write a prescription for the patient, you need to carry out the last stage. Then you can already wear glasses. The patient sits down at a distance of five meters from the table according to which vision is checked. They put on a test frame and through special lenses make a selection. First, on each eye separately (while the second is closed), and then together on both.
Normal refraction, in which all the rays of light are connected on the retina at one point, is called emmetropia. The eye in this case can clearly see all the surrounding objects.
Unfortunately, not everything is completely in nature, and some people have a different kind of refraction (due to acquired or genetic reasons) from emmetropia.
The myopic (nearsighted) eye has a strong ability to refract, which is why the focusing of light rays occurs in front of the retina. The farsighted eye (hyperopic) can slightly refract light, and therefore the focus is behind the retina. These types of refraction do not allow a person to get good visual acuity and clarity, that is, they are indications for its optical correction.
The higher the degree of hyperopia or myopia, the worse the patient’s vision will be. And that means he needs to wear glasses. Such varieties of refractive error are divided into three degrees in ophthalmology: weak - a maximum of three diopters; moderate severity - from four to six; severe - over six diopters.
There is also such a variety of ametropia (a defect in normal refraction) as astigmatism. In this case, the refractive power of the lens and cornea is impaired, and there are deviations in the uniform curvature of the lens and / or cornea, and as a result not only visual acuity suffers, but there are also distortions of objects surrounding the patient.
Astigmatism has such forms as farsighted, shortsighted, and mixed. This form of ametropia is the most difficult to correct. You have to wear glasses all the time.
Optometrist lens selection
As soon as the optometrist has determined visual acuity, first without correction, the patient is offered a trial frame, where lenses with different levels of refraction are inserted in turn, until maximum visual acuity is achieved for each eye. The lenses are scattering (minus) and collective (plus), which depends on the results obtained on the device. In the absence of an autorefractometer in the cabin, the polarity of the lenses is established empirically: weak minus and plus are inserted - a polarity suitable for which an improvement in vision is observed.
For myopic
For nearsighted people, the lens is selected with a minimum refractive power, which will be distinguished by the greatest visual acuity, and with farsightedness - on the contrary, the maximum refraction. First, the lens is selected in turn so that for each eye the visual acuity is equal to 0.8. After that, both lenses are inserted at once - the visual acuity of the binocular should be approximately 1.0. With a difference in visual acuity of the left and right eyes, the maximum difference in the refractive power of the lens should not be more than three diopters, and maybe lower - it all depends on the human reaction. In order to make sure that the selected lenses are transferred normally, you need to give the patient the opportunity to not remove them for some time, read, walk around the office freely.
Why wear glasses with astigmatism?
Astigmatism correction
The most difficult task for an ophthalmologist is the correction of astigmatism. For this purpose, cylindrical lenses are used, which require a long addiction. If astigmatism is high, lenses are selected gradually over an extended period, starting with weak ones. To determine the visual acuity in pathology and choose glasses, they most often use a phoropter, that is, a special addition to a diagnostic ophthalmic device.
Regarding the selection of reading glasses, it must be said that in this case they use other tables that diagnose a person’s vision near. Here are the same rules for selecting lenses: first check the right eye, then the left, at the end - binocular (both eyes at once). It is necessary to focus on approximately the fifth text of such tables, but the final decision will be made taking into account the opinion of the person.
If progressive and bifocal glasses are selected, visual acuity should be diagnosed both close and far. Between these parameters, the difference can be no more than three diopters, while visual acuity is optimal both for close distances and for distant ones.
Pupil distance measurement
As soon as the lenses of the necessary refractive power are selected, the ophthalmologist will measure the interpupillary distance. To do this, use the device with a pupillometer. In its absence - a simple ruler. Measure by a special technique. If the glasses are for distance, this distance should exceed by two millimeters the parameter for glasses used in reading. If the interpupillary distance is incorrectly measured during the manufacture of glasses, their alignment will be disturbed, and wearing them will cause considerable discomfort to the patient.
Prescription for glasses
When all parameters have been determined, the ophthalmologist writes a prescription that lists all the necessary information: the strength of the lenses (cylindrical or spherical, indicating the axes), interpupillary distance, target (for constant wear, correction near or far). It is necessary to store ophthalmic recipes to control all changes in the properties of the eyes.
Lenses should be selected only by a highly qualified doctor, as if the conditions are not met due to wearing glasses, the patient may experience severe discomfort, fatigue, they can provoke a headache and impair vision.
How to wear glasses?
In fact, in order not to spoil the vision, instead of correcting it, you need to use glasses and contact lenses correctly.
Rule 1. Glasses and contact lenses should be selected only by a doctor according to the results of diagnostics carried out on modern equipment.
Rule 2. Buy and order glasses should only be in optics or specialty stores.
Rule 3. Before you start wearing contact lenses, be sure to read the instructions.
Rule 4. If you wear glasses or contact lenses, periodically undergo an eye examination.
Varieties of frames
With the help of a frame, lenses are fixed, allowing for a convenient location, as well as human comfort. They are divided into: semi-rimless - when the rim is only on top; rim - the complete conclusion of the lenses in the rims; rimless - include only lenses and temples connected by screws.
Frames can differ in the material of manufacture and can be plastic, metal and combined. The advantage of frames made of plastic is in lightness, of metal - in reliability and durability. Optical stores currently offer many frames that differ in color, size, style and shape. To choose the most suitable and comfortable to wear glasses, you can try on several types.
The right choice of frames, sizes
The frame should be chosen depending on a number of factors: the type of patient's face, the particularities of vision, design wishes, cost, etc. The basic rules are as follows: lack of compression and discomfort in the nose and temples; glasses should not "go" down when the head is tilted; the glasses should sit evenly and not focus on the asymmetry of the human face.
Choosing reading glasses, you need to take into account the field of view required by the patient. Frames with narrow glasses with bifocal lenses will make it possible to look at long and short distances. Large frames are suitable for working at a computer and reading. They perfectly combine areas for medium and close distances, the lower border is not cut off.
Glasses with progressive multifocal lenses are slightly more difficult to manufacture, so they have a higher cost. However, the high quality of vision at any distance justifies the price. For them, not too narrow round frames are desirable. When buying such glasses for the first time, it is better to take a frame with large lenses to get used to the glasses faster and reduce distortion on the sides.
When choosing glasses for distance, you should pay attention to the frames that cover the completely necessary field of view. They can have different sizes and shapes, however, the distance from the lens to the eyes should be comfortable, while the frame should sit tight. Going straight from large to narrow frames is not worth it, because it will not be very pleasant to get used to.
When choosing rimless or semi-rimless frames, you need to remember that the cost of work in this case can go up significantly. It is impossible to install thin lenses of small diopters into the semi-rimmed frame (plus). There may be an individual order, which will have an appropriate cost. Frames without rims do not have a frame, the necessary rigidity is achieved by more durable lenses or special materials: trivex or polycarbonate. The price of the order increases, but the points are strong and light.
Does the child need to wear glasses?
Eyeglass frames for baby
For children's glasses, the frame must exactly match the size of the head, and also be strong and at the same time light. Be sure to pre-straighten it so that the child can say for sure whether she is sitting comfortably. Soft silicone nose pads will protect delicate baby skin from rubbing, while temples should not squeeze whiskey. Now, in most optical stores, even at their parents' request, they don’t put glass lenses because of their injury hazard and severity. For children's glasses, plastic lenses are recommended. Over time, when the head grows, you need to change the frames. It is extremely undesirable to buy glasses for children in metal cheap frames, the origin of which is unknown, since they can cause allergic reactions of the body.
In the article, we examined how to choose and wear glasses correctly.