In the article we 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 in patients. It is caused by the development of age-related presbyopia (farsightedness) over time. However, there is also a similar need for children and young people suffering from myopia (nearsightedness), astigmatism and hypermetropia (farsightedness).
With all these pathologies, you need to wear glasses.
Vision test, norm and pathology
Examination by an ophthalmologist is painless, simple and quick, it does not require a person to prepare in advance. Arriving at the appointment, you need to talk about problems with the eyes and answer the questions of the doctor. The first stage of the examination is refractometry, which is done using a special apparatus. The person is comfortably positioned behind him, calmly looking straight ahead. With the help of an autorefractometer, the refractive power (refraction) of the patient's eye is established,information about 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 a person. The ophthalmologist receives information about the degree of nearsightedness or farsightedness 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 condition of the cornea, the presence or absence of inflammation processes is determined.
To write a prescription for a patient, you need to complete the last step. After that, you can already wear glasses. The patient sits at a distance of five meters from the table, according to which vision is checked. He is put on a trial frame and, with the help of special lenses, a selection is made. 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 perfect 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 refractive power, which causes light rays to focus in front of the retina. A far-sighted (hyperopic) eye can refract light weakly, and therefore focusing is carried out behind the retina. Such types of refraction do not allow a person to get good visual acuity and clarity, that is, they are indications for his opticalcorrection.
The higher the degree of hypermetropia or myopia, the worse the patient's vision will be. And that means he has to wear glasses. Such varieties of refractive error are divided into three degrees in ophthalmology: weak - a maximum of three diopters; moderate - from four to six; heavy - 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 disturbed, and there are also deviations in the uniform curvature of the lens and / or cornea, and as a result, not only visual acuity suffers, but also there are distortions of objects surrounding the patient.
Astigmatism has such forms as farsighted, nearsighted and mixed. This form of ametropia is the most difficult to correct. You will have to wear glasses all the time.
Choosing lenses with an optometrist
As soon as the ophthalmologist has determined the visual acuity, first without correction, the patient is offered a trial frame, where lenses with different refractive levels are inserted one by one until the maximum visual acuity is reached for each eye. Lenses are taken 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 - such a polarity is suitable at which vision is improved.
For the nearsighted
For nearsighted people, the lens is selected with a minimumrefractive power, which will differ in the greatest visual acuity, and with farsightedness - the opposite is true, the refraction is maximum. First, a lens is selected in turn in such a way that visual acuity becomes 0.8 for each eye. After that, both lenses are inserted at once - binocular visual acuity 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 lenses should be no more than three diopters, and may be lower - it all depends on the reaction of the person. In order to make sure that the selected lenses are transferred normally, you need to give the patient the opportunity not to take them off for some time, read, walk around the office freely.
Why do people 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 habituation. If the astigmatism is high, the lenses are fitted gradually over an extended period, starting with the weak ones. To determine visual acuity in pathology and choose glasses, they most often use a phoropter, that is, a special addition to a diagnostic ophthalmological device.
Regarding the selection of reading glasses, it must be said that in this case other tables are used that diagnose a person's near vision. The rules for choosing lenses are the same here: first, the right eye is checked, then the left, and at the end - binocular (both eyes at once). You need to navigate approximatelyon 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 near 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 long distances.
Measuring distance between pupils
As soon as the lenses of the desired refractive power are selected, the ophthalmologist will measure the interpupillary distance. To do this, use the device pupillometer. In its absence - a simple ruler. Measurement is made according to a special technique. If glasses are for distance, this distance must exceed by two millimeters the parameter for glasses used in reading. If the interpupillary distance is incorrectly measured during the manufacture of glasses, their centering will be disturbed, and wearing them will cause considerable discomfort to the patient.
Recipe for glasses
When all the parameters have been determined, the ophthalmologist writes a prescription, which indicates all the necessary information: lens power (cylindrical or spherical, with axes), interpupillary distance, goal (for constant wear, correction near or far). Ophthalmic prescriptions must be kept to control all changes in the properties of the eyes.
Lenses should be selected only by a highly qualified doctor, because if the correct conditions are not observed due to wearing glasses, the patient may experience severe discomfort, fatigue, they can provoke a headache and impair vision.
How to wear glasses correctly?
In fact, in order not to spoil your 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 based on the results of diagnostics carried out on modern equipment.
Rule 2. Buy and order glasses only in opticians or speci alty stores.
Rule 3. Before you start wearing contact lenses, be sure to read the instructions.
Rule 4: If you wear glasses or contact lenses, get your eyes checked periodically.
Variety of frames
With the help of the frame, the lenses are fixed, allowing for a convenient location, as well as human comfort. They are divided into: semi-rimmed - when the rim is only on top; rim - complete enclosing of lenses in rims; rimless - includes only lenses and temples connected by screws.
Frames may differ in the material of manufacture and be plastic, metal and combined. The advantage of frames made of plastic is lightness, while those made of metal are reliability and durability. Optical shops now offer a variety of 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.
Correct choice of frames, sizes
The frame must be chosen depending on a number of factors: the type of the patient's face, vision, wishesby design, cost, etc. The basic rules are as follows: no pressure or discomfort in the area of the bridge of the nose and temples; glasses should not "go" down when tilting the head; glasses should sit evenly and not focus on the asymmetry of the human face.
When 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 close 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 somewhat more difficult to manufacture and therefore more expensive. However, the high quality of vision at any distance justifies the price. Not too narrow round frames are desirable for them. When buying such glasses for the first time, it is better to take a frame with large lenses in order to get used to the glasses faster and reduce distortion on the sides.
When choosing glasses for the distance, you should pay attention to the frames that cover the entire field of view. They can have different sizes and shapes, but the distance from the lenses to the eyes should be comfortable, while the frame should sit tight. You should not immediately switch from large to narrow frames, as it will not be a very pleasant addiction.
When choosing rimless or semi-rimless frames, you need to remember that the cost of work in this case can go up a lot. It is impossible to install thin lenses of small diopters (plus) in a semi-rimmed frame. Can be custom order which will havethe corresponding 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 glasses are durable and light.
Should my child wear glasses?
Children's Spectacle Frames
For children's glasses, the frames must exactly match the size of the head, and also be strong and at the same time light. Be sure to straighten it first so that the child can tell for sure whether it sits comfortably. Soft silicone nose pads will protect delicate baby skin from chafing, while the temples should not squeeze the temples. Now, in most optical salons, even at the parental request, glass lenses are not installed because of their injury risk and severity. Plastic lenses are recommended for children's glasses. Over time, when the head grows, you need to change the frames. It is highly undesirable to buy glasses for children in cheap metal frames, the origin of which is unknown, as they can cause allergic reactions in the body.
In this article, we looked at how to choose and wear glasses correctly.
