The radius of curvature is one of the important ones. We understand: what is the radius of curvature (base curvature) and how to measure it? Which lenses are right for you

Determining the curvature of the eyeball is the basic procedure for choosing a corrective product from an ophthalmologist. The lens fits snugly to the cornea, thereby eliminating the ingress of dust, small particles. They should fit snugly, but not too tightly, so determining the curvature plays a crucial role in creating a comfortable and secure fit.

Why define curvature and what it characterizes

With an incorrectly defined curvature, there are two unfavorable developments of events:

corrective product presses on the apple;
the eyepiece has a low degree of adhesion.

If the contact lens has excessive friction on the cornea:

there is a violation of blood circulation, which leads to vascular dystrophy;
small scratches appear, turning into scars, microoutflows.

Visually, redness of the eye occurs, unpleasant sensations of the presence of something foreign in the eye. Many complain that "like sand was poured." If the symptoms are ignored, inflammatory processes can begin.

If the eyepiece moves freely:

the lens may fall out of the eye;
the correct perception of the image is distorted;
the corrective product moves easily from the upper to the lower eyelid.

The material also affects the radius of curvature. For example, hydrogel models are more plastic than silicone counterparts. Therefore, when choosing, this factor is also taken into account.

What does it affect

As noted above, the radius of curvature indicates the degree of convexity of the product and is expressed in millimeters. BS provides complete convenience, comfort and essential assistance in correcting an ophthalmic defect. It affects the general condition of the eyeball, vascular tone and the correctness of vision correction.

Read about aphakia in the material.

How to choose a radius

The process of refractokeratometry is carried out only by a doctor in a specialized office. The refractometer displays the degree of curvature of the cornea on the monitor screen, without causing discomfort and discomfort during the procedure. The procedure time is 5-7 minutes.

After receiving the parameters, the doctor selects the desired lens and gives it to the patient for fitting. This is how the adhesion density is determined. The slit lamp helps the ophthalmologist to see the degree of fit of the device. For additional verification, fluorescein is dropped into the eye, glowing and flickering under ultraviolet light.

The intensity of the glow shows how perfectly matched the corrective eyepiece. Only after that a prescription is issued with an exact indication of the diagnosis, diopters, radius of curvature and diameter.

Consequences of the wrong choice

The consequences of an incorrectly selected contact device can be very unpleasant and in some cases lead to serious health problems. In addition to selecting the technical parameters of the lens from the doctor, you should also listen to your feelings on the stiffness, degree of moisture and individual intolerance to individual components or solutions.

If the curvature is less than necessary, as noted above, there will be free movement inside the eye, the lens will fall out. There may be irritation, tearing and itching under the eyelids.

With a tight fit, more serious negative consequences occur:

decrease in air exchange, degeneration of capillaries;
lack of natural irrigation in the form of tears;
doubling of the image and pain in the eyes.

Split image

Prolonged hypoxia becomes a catalyst, including inflammatory processes. In advanced cases, they require surgical intervention.

How to know if your lenses are the right fit

Sensitive people, experiencing any discomfort, begin to fear the correct selection of the curvature of the lenses. First of all, it is worth understanding that the ideal contact of the corrective product and the cornea is affected by:

the internal state of the body, possible cold symptoms;
the level of humidity of the surrounding air;
windiness;
adaptation period (if the couple is dressed for the first time).

According to studies, the adaptation process occurs within two or more weeks, depending on the susceptibility of the body. You should also monitor the cleanliness of the product and the replacement period.

If these parameters are observed, but the discomfort does not go away when worn (itching, headaches and eye pain appear), then you should consult a doctor for a consultation.

With a properly selected pair, the lenses are not felt on the cornea of the eye, do not slip or stick. For comfortable wear, natural irrigation is enough.

How can you tell if the lenses are the right fit?

It is quite difficult to independently determine the correct fit of contact lenses, so it is also better to contact a specialist with this issue. Soft products should be located exactly in the center of the eye, that is, completely cover the iris of the eye, protruding from it by about 1.5 mm, and move no more than 1.5 mm when the eyeballs move. If you move the lens up through the skin of the lower eyelid, it should quickly and easily return to its place - this test is called a push-up test.

The soft lens should be positioned exactly in the center of the eye.

Loose fit is characterized by excessive mobility of the lens - when blinking, it shifts by 2 mm or more, constantly shifts relative to the center of the eye, does not cover the cornea, and its edges go under the upper eyelid. In this case, visual acuity deteriorates, and the mucous membrane of the upper part of the eye is injured by the edge of the product.

A too tight fit is more dangerous than a loose one - the lens is too tight to the eyeball, does not return to its place during a push-up test (an attempt to move it through the lower eyelid). A sign of such a fit is a border on the surface of the eye, which remains after the lens is removed.

The partial pressure of oxygen in the cornea when using a soft contact lens with a thickness of 0.2 mm and the diffusion capacity of the lens with respect to oxygen. Eyelid raised

There are a number of symptoms that indicate that the lenses are not fitted correctly. These include:

increased tearing;
redness, inflammation and itching of the eyes;
painful and difficult movement of the eyeballs;
headaches, manifested even after a slight strain of vision;
blurred images, decreased visual acuity.

Incorrect lens fitting can lead to dry eye syndrome

If any of the above symptoms appear, you should consult a doctor to replace contact lenses, otherwise the condition of the eyes may worsen significantly. Do not forget about the appropriate care of the lenses - the products must be washed with disinfectant solutions and stored in special containers.

Rules for the care of contact lenses

The correct selection of a lens, taking into account the curvature of its radius and other parameters, is the main condition for good vision and eye health, so you need to buy optical correction products only after consulting a specialist.

How to choose the right contact lenses?

In order not to make a mistake with the choice of an optical product, in addition to curvature, it is necessary to pay attention to a number of parameters:

Type of ophthalmic abnormalities (myopia, hypermetropia, astigmatism, etc.). Each type of anomaly requires an individual approach and certain lenses. The product is selected depending on the clinical nuances of the pathology,
optical power. One of the main characteristics of corrective products, measured in diopters with a minus or plus sign. The indicator may be different for the left and right eye, this must be taken into account when choosing lenses,
Diameter. The distance between the two edges of the eyepieces. To measure it, an imaginary line is drawn from one end to the other, crossing the center point. For soft lenses, the diameter is from thirteen to fifteen millimeters. Most often, doctors opt for an average: from 13.8 to 14.5 mm.,
The thickness of the contact lens. It is measured in the central part. "Plus" products have a maximum indicator in the middle, but at the edges the eyepiece is much thinner. "Minus" models, on the contrary, are thick in the peripheral areas.

An equally important role is assigned to the radius and width of the slip zone. With astigmatism, when a person needs unique toric lenses, the tilt axis and the optical power of the cylinder are added to the list of important characteristics.

Particular attention should be paid to the curvature of the lens in keratoconus. This pathology changes a similar indicator of the cornea

If you purchase a product with inappropriate parameters, you risk even more damage to eye health.

To understand how suitable this or that model is, use the "fitting" and purchase a trial set in order to be able to determine the result as reliably as possible. The lens is put on for thirty minutes, waiting for increased tearing and inflammation to pass. Only after that, the fit and mobility of the eyepiece, as well as the sensations of the patient, are evaluated.

How to determine the normal radius of curvature of contact lenses

It is impossible to determine this parameter on your own. With a normal fitting, it is impossible to know exactly what its indicators are. The selection of the correct contact optics should be carried out by an ophthalmologist, and not by a salesperson in a store.

Photo 1. An example of changing the required curvature of a contact lens for a different shape of the cornea.

During the examination, the doctor checks the autorefractometry method. The method determines the type and degree of visual impairment using infrared radiation. As a result, the degree of astigmatism and refraction is revealed. And also, an examination of the fundus is carried out using a slit lamp, to determine the correctness of the measurements taken.

After that, the doctor puts on test optics, having previously dropped fluorescein into the eyes. Illuminating with an ultraviolet source evaluates the correct fit of the product, the distribution of the medicine over the eyeball. Only after the examination, the specialist writes out the right prescription, which accurately indicates the optical power, diameter and main bend, which are ideal for the eyes.

What makes the right choice

The correct choice of the main curvature of the means of vision correction will give, first of all, certain guarantees for the patient:

Wearing comfort. There will be no lens sensation on the eyes. It will not move when blinking and the possibility of losing it will be excluded, which means that the vision will remain clear.
Eye safety and health. Incorrect selection of optics causes discomfort, and also leads to dangerous consequences, such as corneal hypoxia, which is detected as edema due to the inability to get oxygen.

The consequences of an incorrectly selected radius

With the wrong choice of corrective means, vision deteriorates and the following problems arise:

deterioration of well-being;
decrease in working capacity;
frequent headache;
possible lacrimation, irritation of the cornea and conjunctiva, itching;
hypoxia;
corneal edema;
decrease in visual acuity.

Blinking becomes painful and feels like sand in the eyes. After removing the unsuccessfully selected optics, it is clear that the eyeball turned pink. This symptom provokes hemorrhage in the anterior part of the visual organ. Incorrect selection of the size or insufficiently well-chosen lenses lead to the occurrence of infectious diseases of the eyes. There is a decrease in local immunity, damage to the integrity of the mucous membrane or sclera, which leads to infection.

A convex lens puts pressure on the blood vessels of the eye, disrupts the nutrition of its individual parts and the process of tear exchange. In this case, the tear does not wash the cornea, and vision becomes unstable.

Less convex - increases the likelihood of losing a contact lens, increases lacrimation. Blinking becomes painful, the presence of a foreign body appears. Due to the non-compact fit, the optics will not fully correct vision.

To avoid such unpleasant complications, it is necessary to choose the right bend.

Important! A deviation of no more than 0.2 microns is permissible. Such vision correction devices are allowed to be worn if they do not cause much discomfort.

Differences across brands

It is also necessary to know that contact optics produced by one brand differ in their characteristics from contact vision correction products of other brands. The parameter 8.5 mm for one manufacturer may correspond to 8.6 mm, and for another - 8.4 mm. When switching from one model to a new one, you need to consult an ophthalmologist.

What to do if the product has already been purchased, but the parameter does not fit?

With a difference of no more than 0.2 mm, nothing terrible will happen - such CLs can be worn without harm to the eyes. But it happens that the products of one manufacturer with a BC radius of 8.4 mm correspond to the products of another with a radius of 8.5 mm. If the deviation between brands exceeds 0.2 mm, then such products cannot be worn!

Symptoms of inconvenience when wearing optics with inappropriate curvature:

Difficulty in the mobility of the CL, if it is more convex. In such cases, the eye is constantly tense, its blood vessels are compressed, which inevitably leads to redness. Also, tear exchange may be impaired, since the tear will not be able to pass through the lens that is closely adjacent to the cornea, and the risk of inflammatory processes will increase. Vision may be unstable.
Increased mobility of the CL, if it is less convex. In the case when the BC radius of the contact lens is larger than necessary, it becomes too mobile. Then it can fall out of the eye, cause watery eyes or damage the cornea. This happens because the flat lens easily and imperceptibly moves away from the cornea. It is felt only when blinking, when it begins to touch the upper muscles of the eye. Then there will be a feeling that something has got into the eye, itching and redness.

To avoid all this, it is necessary to buy CL according to the prescription, which will indicate all the parameters necessary for the correct choice. Then wearing them will only be a joy and refractive errors will not be a hindrance to a life saturated with bright colors and colors!

Perhaps in the near future the choice of CR will not depend on the BC radius! Video:

How to choose the right contact lenses

Choice of contact lenses

The correct choice of contact lenses depends not only on the radius of their curvature, but also on a number of parameters.

Type of visual impairment (farsightedness, astigmatism, myopia). Each type of pathology requires the selection of contact lenses with certain characteristics, depending on the clinical features of its course.
optical power. One of the main characteristics, measured in numerical values (diopters) with a "+" or "-" sign, on which the clarity of the patient's vision depends. Its value may differ for the left and right eyes both in numerical value and in sign.
Diameter. The distance between the edges of the product - to measure it, an imaginary line is drawn from edge to edge through the center point. The standard diameter of soft lenses is from 13 to 15 mm, most often used devices with a diameter of 13.8-14.5 mm.
The thickness of the lens (measured in the central part). As a rule, "plus" optical means are thicker in the center and much thinner at the edges, while "minus" ones, on the contrary, are thin in the center and thicker at the periphery.

How to choose contact lenses

In addition, the radius and width of the sliding zone play an important role, and in case of astigmatism, when the patient needs special toric lenses, the optical power of the cylinder and the axis of inclination are added to the list of parameters.

Video: How contact lenses are selected

To determine how lenses with certain parameters are suitable in a particular case, it is better to use a trial set, which will allow you to “try on” the devices and evaluate the result.

Lenses need to be tried on first.

Table for the selection of trial lenses.

visual impairment	Curvature radius, mm	Radius of width and sliding zone, mm	Diameter, mm	Thickness in the central area, mm	Refraction (optical power), diopters
Myopia	8,0	9.0 x 0.5	13,5-10	0,17	-5 to -15
	8,2	9.2 x 1.0	13,5-10	0,17	-5 to -15
Keratoconus	7,2	7.5 x 1.0, 7.8 x 0.5, 8.1 x 0.5, 8.4 x 0.5, 8.7 x 0.5	15,5/9,5	0,35	-18
	7,4	7.9 x 1.5, 8.4 x 1.0, 8.9 x 0.5	15,5/9,5	0,35	-10 to -15
	7,6	8.1 x 1.5, 8.6 x 1.0, 9.1 x 1.0	15,5/8,5	0,35	-10 to -15
Afakia	8,0	9.0 x 0.5	13,5/9,0	0,25	+10 to +17
	8,2	9.2 x 1.0	13,5/9,0	0,25	+10 to +17

Silicone hydrogel lenses

After choosing trial lenses, they are tried on - the products are put on the patient, after which they wait half an hour until lacrimation and inflammation pass, after which the density of fit and mobility of the product, as well as the patient's sensations, are assessed.

What lens curvature radius is right for you

Sometimes choosing lenses for the eyes is not an easy task. You need to understand the variety of models and understand which ones are right for you. In order for the purchase of contact lenses with diopters to be successful, you need to know what the basic curvature is. It is about her that we will tell in this article.

What is lens curvature and why is it needed?

Base curvature characterizes the inner curved surface of the lens itself. In order for the eye to feel as comfortable as possible, the lenses must fit perfectly on the convex surface of the cornea.

This is what avoids hypoxic visual impairment and wearing discomfort.

If the eye lenses are too convex, they will squeeze the eyeball unpleasantly, and, conversely, if they are too flat, they may not sit tight enough.

How to choose the right curvature of contact lenses?

The exact value of this parameter can only be found out at an appointment with an ophthalmologist. The doctor will measure the refractive power of the eye using autorefractometric devices and determine your individual parameters.

During computer diagnostics, an infrared beam of light is directed to the surface of the eye and its reflection is recorded.

The technology gives a complete picture of the parameters of the cornea and determines which contact lenses for the eyes are worth buying and which are not.

Most people have a curvature value between 8.3 and 8.8. Such eye lenses can be easily found in stores or ordered online.

But when this parameter is very different from the standard values, it is worth considering the manufacture of lenses to order. Doctors do not recommend buying models that differ from the required size by more than 0.2.

After all, the constant wearing of inappropriate contact lenses can cause a sharp deterioration in vision.

To determine if a pair of contact lenses suits your eyes, you can use a simple test. With clean hands in front of the mirror, move the lens up slightly. Models that fit well move easily 1-1.5 millimeters and quickly return to the standard position.

Why is it important to buy the right contact lenses?

If the eye lenses are not fitted correctly, they either compress the cornea and interfere with the flow of tears, or move when you blink. In any case, this can lead to visual impairment. Models that are too small can lead to hypoxia and even corneal corrosion.

And too wide can injure the inner surface of the eyelid and cause headaches.

That is why it is extremely important to responsibly choose lenses for the eyes and contact a professional. Only he will determine which lenses for the eyes will be the best option.

Main characteristics

When choosing, you should pay attention to the following parameters of contact lenses:

diopter (optical power);
radius of curvature;
diameter;
oxygen permeability;
moisture contents;
type, design features and material;
wearing and replacement mode.

optical power

Optical power is determined by diopters. The optical zone itself is located in the center. The correction is more precise. This means that contact lenses have less optical power than glasses. Values for the eyes can differ both in magnitude and in sign + or -.

Radius of curvature and diameter

The radius of curvature itself largely depends on the structural features of the eyeball. When on the cornea, you must make sure that their shape and size match. In standard cases, the base curvature in both eyes should be the same.

If everything is chosen correctly, then the curvature of the glass and the cornea of \u200b\u200bthe eye will clearly match. The base curvature of contact lenses is the ratio of the back of the lens to the central, spherical shape. It is used to determine the radius of curvature. Curvature of the front part - diopter. If the back is non-spherical, then the radius of curvature will increase accordingly from the center to the edges.

To find out the exact indicators, the ophthalmologist, using computer diagnostics, conducts a complete examination of the patient's cornea. This method is called autorefractometry, which is based on infrared radiation.

If the patient feels discomfort, this may mean that the chosen radius of curvature is not suitable. Often the diopters of different manufacturers may not match. Therefore, if a person first wore lenses from one company, and then acquired the same ones, but from another company, this can cause discomfort.

If the deviation of the curvature index is more than 0.2, it is already contraindicated to wear lenses. If they are more prominent than the patient needs, then eye strain increases. Blood vessels are compressed, which leads to redness of the eye. The threat of inflammatory diseases increases, as tear exchange will be difficult.

On the contrary, if the radius of curvature is greater than desired, the mobility of the lens may increase. She can easily move away from the cornea, damage it, and then the person will not see anything. From this it follows that one of the main parameters when choosing is the basic curvature of contact lenses. How to determine it so that they fit in the best way, only the doctor knows.

The diameter of a contact lens is the distance between the edges, which is measured through the center. The comfort of use will depend on the correct selection of the diameter.

Types of contact lenses

Depending on the purpose and design, the following types are distinguished:

traditional - they are distinguished by transparency and softness, they correct vision only through a single optical power;
toric - less transparent, but still soft, used for complex correction with two optical powers;
multifocal - have three zones for clear vision: for near, far and medium distance;
color - there are both with diopters and zero, for example, for people with good eyesight who want to change.

Depending on the material, they are divided into hydrogel, silicone hydrogel and hypergel.

Hydrogels are very comfortable to wear, as they contain a fairly large amount of water. You can only wear them during the day.

Silicone hydrogels contain silicone, which provides a high level of oxygen transmission, and hydrogel - to moisturize the cornea. Recommended for wearing both during the day and at night. This is due to their low water content.

Hypergel - made of innovative material HyperGel. They have a high water content with a high level of oxygen transmission. This ensures maximum hydration and wearing comfort.

Oxygen permeability and moisture content

These indicators determine the access of oxygen to the cornea itself. As for hydrogel glasses, the more water they contain, the greater their oxygen permeability. In hydrogen-silicone, the oxygen permeability level does not depend on the water content in them. Silicone provides oxygen transmission, and hydrogels provide comfortable use due to water.

What threatens the wrong choice of lenses?

Human eyes will be under constant load. Many people think that this is normal when using contact lenses, but this is a mistake. On the contrary, if you choose lenses in the most correct way, the numerical value of the inner side of which will be comparable to the radius of the eyeball, then no discomfort and overload of the visual organs should be felt.

Trying on lenses

If it is wrong to carry out the selection of contact lenses along the radius, this will have a negative impact on the entire visual system. Experts say that the maximum allowable deviation of the numerical value of the radius of the contact lens from the value of the indicator of the eyeball is 0.2. That is, if a person has an index equal to 8.4, then the index of the lens radius can have a value equal to 8.6, but not more.

If you choose the wrong contact lens, troubles such as:

Difficulty in moving the eyes.
Sensation of pain when blinking.
Noticeable visual impairment.
Constant tearing during the use of contact lenses.

The value of the curvature of the lenses - how to choose

The concept of the radius of curvature

The radii of curvature of the contact optics and the cornea must be aligned, otherwise the product will not fit snugly or press on the surface of the eye. In order not to damage your eyes, you must remember that along with optical information, physical information is also indicated on the package - the basic curvature. It is measured in millimeters and can also be indicated on the products themselves. It is clear that smaller values mean more curvature of the surface, and vice versa - larger values of the radius of curvature, these are flatter contact lenses.

Fluctuations in the radius of curvature of the cornea in humans range from 7.5 millimeters to 9.5. First of all, it depends on the structure of the eye and its size, and secondly, on the presence of visual impairments in a person:

with myopia, the cornea is more convex;
keratoconus - thinning of the cornea determines its conical shape.

The vast majority of contact lenses available in the distribution network have a spherical shape with a base curvature at the level of average values - from 8.3 millimeters to 8.8. The easiest way to choose contact lenses is for those people whose corneal curvature radius fits within the indicated limits. Acuvue TruEye, Optima F.W., Acuvue Advance and Acuvue 2 optics manufacturers produce contact lenses in this range.

Before purchasing optics, you need to visit an ophthalmologist and clarify the radius of curvature of the surface of your eyes. If it does not fit into the standard, the optics can be made to order. If the difference in curvature between commercially available lenses and those entered into the ophthalmologist's prescription does not exceed 0.2 millimeters, you can safely purchase standard ones - most people do not feel any discomfort in such cases.

In addition to optics with a spherical bend, spherical-cylindrical lenses are made - toric, which are worn with astigmatism. Such products consist of two bulges located at different angles and have a double curvature marking.

The consequences of an incorrectly chosen base curvature of the lens

There are two options for an erroneous choice: either the bending radius is less than the required one, or it is greater. In both cases, wearing such products is unacceptable for the following reasons. If the base curvature is less than required (flatter product):

the film will be unstable on the cornea, shifting, will cause irritation, itching and lacrimation;
a small bulge will not allow the film to be fixed on the surface of the eye, and it can damage the cornea or simply fall out;
with a loose fit to the cornea, the film will not be able to fulfill its purpose - it will not be able to correct vision.

If the base curvature is greater than required (the film is more convex):

the eye will be in a compressed state, which will lead to a decrease in gas exchange and tear exchange in the cornea, and it will become susceptible to inflammatory processes;
loss of visual stability, irritation of eye tissues and intense tearing will also be the result of exposure to more convex products.

Color contact lenses

Colored soft lenses have become extremely popular in recent years. Their choice is simply huge, and any self-respecting manufacturer has a variety of palettes.

You can easily transform yourself by buying decorative lenses, create a new style and improve your own mood. Colored lenses are also available without diopters, so they are suitable even for those who do not suffer from visual impairments.

Colored contact lenses can also correct visual impairments if needed. The diopter range of products is very large, so they will suit every person.

The use of care products depends on the period of wearing lenses, in connection with which the doctor will advise the necessary solutions, tablets or drops. These preparations will help to keep not only the lenses themselves, but also the health of your eyes.

DO YOU STILL THINK IT IS HARD TO GET CLEAR VISION BACK?

Judging by the fact that you are now reading these lines, victory in the fight against blurred vision is not on your side yet ...

Have you thought about surgery yet? It is understandable, because the eyes are very important organs, and their proper functioning is the key to health and a comfortable life. Sharp pain in the eye, clouding, dark spots, sensation of a foreign body, dryness, or vice versa, lacrimation ... All these symptoms are familiar to you firsthand.

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Competent selection of contact lenses (CL) is not only matching diopters, but also matching the curvature of the cornea. This is an individual parameter determined by an ophthalmologist and ensures a normal fit of the lens on the eye.

Each contact lens has a certain internal dimension - the base curvature. It should correspond as much as possible to the curvature of the cornea of the eye. Its radius varies from 7.8 to 9.5 mm (the smaller, the "cooler" the lens), but this is purely individual for each person. The most common is 8.6-8.8 mm. The base curvature of contact lenses in the central part of the back surface for most of them is spherical, characterizing its radius of base curvature (BC).

If the fit of the contact lens to the eye is inadequate, this can cause discomfort and complications. This can be avoided if, before their first purchase, they are examined by an ophthalmologist.

The basic curvature of lenses is a fundamentally significant parameter that must be taken into account when buying them. In the recipe, it is denoted by the letters BC.

How is this parameter determined?

An ophthalmologist can take measurements on an autorefractometer. This is followed by fitting trial CLs with parameters suitable for the patient. The doctor using a slit lamp should evaluate the correct fit and mobility on the eye. To do this, a special solution "Fluorescein" is instilled, which, when illuminated with ultraviolet light, allows you to most fully assess the distribution of the agent under the contact lens and its fit.

After a prescription is written, which should indicate:

Diameter.
BK radius.
optical power.

These parameters will be needed to purchase the correct CL.

How important is the correct selection of this parameter?

A well-defined basic curvature of CL is significant for a person who decides to use them. This will provide:

Comfortable wearing. The lens will not be felt by the eye, its mobility when blinking will be within the normal range. This means that the risk of its loss will be excluded, and the vision will be extremely clear.
Safety and health of the eyes. The use of CLs with inappropriate curvature can cause discomfort, hypoxia and corneal edema, and eye infections.

That is why it is very important to choose CL with the correct parameters. Some lens manufacturers produce only standard products. This somewhat limits the choice. After all, even if the product is suitable for all other parameters - material, gas permeability, degree of moisture, etc., then an unsuitable BC radius will still force you to abandon the brand you like.

But most lens manufacturers take care of their customers as much as possible and produce CLs in several versions. For example:

Acuvue TruEye - models available with a radius of 8.5-9.0 mm
Acuvue Advance and Acuvue 2 are products from Johnson & Johnson, the BC radius varies between 8.3-8.7 mm.
Optima FW - base curvature starts at 8.3 mm and ends at 9.0 mm (different lines).

What to do if the product has already been purchased, but the parameter does not fit?

Symptoms of inconvenience when wearing optics with inappropriate curvature:

Difficulty in the mobility of the CL, if it is more convex. In such cases, the eye is constantly tense, its blood vessels are compressed, which inevitably leads to redness. Also, tear exchange may be impaired, since the tear will not be able to pass through the lens that is closely adjacent to the cornea, and the risk of inflammatory processes will increase. Vision may be unstable.
Increased mobility of the CL, if it is less convex. In the case when the BC radius of the contact lens is larger than necessary, it becomes too mobile. Then it can fall out of the eye, cause watery eyes or damage the cornea. This happens because the flat lens easily and imperceptibly moves away from the cornea. It is felt only when blinking, when it begins to touch the upper muscles of the eye. Then there will be a feeling that something has got into the eye, itching and redness.

Perhaps in the near future the choice of CR will not depend on the BC radius! Video:

How do you buy CL? Do you pay attention to the radius of curvature when buying them? We are waiting for your answers in the comments!

One of the most important conditions for the selection of contact lenses is to determine the radius of their curvature. This parameter directly affects the comfort and safety of using optics. An incorrectly selected radius can not only cause visual impairment, but also cause more serious problems, such as corneal hypoxia.

What is the radius of curvature in contact lenses?

Means of contact correction of vision are put on directly on the cornea of the eye, so they must repeat its shape as accurately as possible. The radius of curvature is a parameter that characterizes the convexity of the inner surface of an optical product. The smaller this indicator, the more convex it is. Accordingly, with a large radius of curvature, the lens will have a flatter shape. Some people mistakenly believe that it is enough to know only the required diopters (optical power) to buy contact correction products, but this is not so.

The radius of curvature is one of the most important parameters in the selection of these products.

Why is it important to choose the right radius of curvature for contact lenses?

How does the radius of curvature affect the convenience and safety of using optics? If this parameter is not large enough, the fit will be very tight. This will lead to increased tension in the eyeball. The blood vessels will not be able to receive the necessary amount of oxygen, which will inevitably cause redness of the eyes and may even cause hypoxia. A lens with an excessively large radius, on the contrary, is excessively mobile, which directly affects the usability. Products will fall off with sharp turns of the head. In addition, they can cause inflammatory eye diseases due to increased friction.

Contact lenses: how to choose the radius of curvature?

Many people are interested in what is the radius of curvature and how can you determine it yourself? The convexity index of optical products ranges from 8.3 to 8.8 mm. This parameter is very individual, since it directly depends on the structure of the human eyeball.

It is impossible to independently determine the radius of curvature of contact lenses at home - this will require special high-precision equipment.

Before you know the radius of curvature, you will need to undergo a comprehensive examination in the office of an ophthalmologist. This computer procedure is called autorefractometry. It takes only a few minutes and does not cause pain.

A refractometer examines the cornea in detail. The computer records data before and after the emission of infrared light, which is reflected from the retina. Then it analyzes them and issues a printout indicating the required parameters. Now you know what the radius of contact lenses is and how to determine this indicator.

During the computer examination, the ophthalmologist will determine:

Required diopters (optical power of lenses).
Radius of curvature (for the left and right eyes).
Distance between pupils.
Additional parameters (diameter, etc.).

It should be noted that, as such, the concept of "standard radius of curvature" does not exist. This indicator is selected individually, taking into account the characteristics of the patient's visual system.

What else to look for when choosing optical products?

When buying lenses, you should also pay attention to the mode of wearing them and the replacement schedule. The most safe and hygienic are considered one-day, which do not require care with a solution. It is enough to put them on in the morning, and in the evening take them off and dispose of them. Planned replacement models can be worn for 2 weeks or more. They are cheaper and at the same time provide high clarity of vision, however, they need systematic cleaning, since various contaminants and deposits accumulate on their surface during use. Daily wear lenses must be removed at night. For people with an active lifestyle, a more practical option has been developed. These are models with a flexible, prolonged and continuous wearing mode. They can be left overnight, and also used without removing up to 7 and 30 days. Before this, it is necessary to consult with an ophthalmologist.

When choosing lenses, you should also take into account the indicators of oxygen permeability and moisture content. They directly affect the comfort and safety of use.

It is labeled B.C. on the packaging. In Dailies AquaComfort Plus it is 8.7, in Acuvue Oasys it is 8.4.

What else to consider when choosing means of contact correction?

Wearing mode (flexible, daily, prolonged, continuous).
Replacement schedule (one-day or planned replacement model).
Indicators of oxygen permeability and moisture content.

On the site you can profitably order ophthalmic products from different manufacturers. Successful purchases!

Contact lenses allow you to conveniently correct your vision, since they are practically not noticeable on the eyeballs, and at the same time, you can run, go swimming, and fully engage in sports in them. Modern youth hobbies involve many active actions that cannot always be provided when using glasses.

One of the main parameters of lenses is the value of the radius of its curvature. You can usually find it on the packaging marked BC.

What can the radius of curvature of contact lenses affect?

First, it is worth mentioning the fit of the lenses. If the radius is too small, the lens can sit too tightly and thus cause further complications. The necessary amount of oxygen does not enter the eye tissues, which leads to swelling of the cornea and other serious consequences. If the radius is larger than desired, then the lens will not be fixed enough on the eye and will fall out, which can cause irritation, since the inner surface of the contact product will rub the cornea. Based on this, it is worth noting that the correct selection of the radius of curvature is a guarantee of the good functioning of your visual organs and safety when wearing lenses.

For a more correct selection of contact lenses, you need to have some ideas about their device. The lens has two sides - outer (optical) and inner (designed to fit the lens). The characteristic we are considering is a curved part of the inner side of the product and is selected accordingly for the radius of curvature of the cornea.

How to determine the radius of curvature of contact lenses

It is impossible to determine the radius of curvature yourself, since such a procedure is carried out only using special tools. However, independent actions can be harmful to eye health. In order to correctly determine the value of this parameter and make the choice of the most suitable lenses, it is better to contact a medical institution or specialists in optics.

First, an ophthalmologist or otometrist, using modern equipment, determines the optical characteristics of your visual organs. During this study, a beam of infrared light is directed to the eye in order to examine the surface of the cornea. The obtained results are processed and on their basis the required values of the radius of curvature are revealed. This process does not take much time.

At the next stage, an ophthalmologist or optometrist tries on and finds the optimal set of lenses that meet the required parameters. This procedure takes place on medical equipment called the Slit Lamp. With the help of it, the specialist determines the correct fit of the lenses, as well as visual acuity in them.

After passing these studies, an ophthalmologist or optometrist writes a prescription for contact lenses, which includes the name of the product and its main characteristics. You need to purchase and wear only such contact products, the parameters of which and the name are prescribed in the prescription, otherwise further vision problems may occur.

How to choose the right radius of curvature for contact lenses

If during a visit to an ophthalmologist you were prescribed a prescription after going through all the procedures, then it will not be difficult to choose the desired curvature, since the specialist will write all the necessary information. In the process of purchasing lenses in a store, you will only need to select the same parameters as in the prescription or if you purchase them online, then as in the field with characteristics.

If you know the magnitude of the curvature of some lenses, is it possible to purchase another pair with the same parameters yourself? It is forbidden. The shape of the lens changes depending on the base curvature radius and diameter. In addition, lenses made from other materials and manufactured using different technologies may have different fit on the surface of the eyes.

How to find out and choose the right size contact lenses that are suitable for your eyes? What is the diameter and radius of the base curvature of a contact lens? Should contact lenses be sized to fit the cornea of the eye?

In this article, we will look at an important and frequently asked question that concerns the correct selection of the size of a contact lens, determining the correct parameters.

Determining the size of a contact lens

If the lens diameter is not correct

If the lens diameter is not correctly selected, then the lens fit will either be loose, if the diameter is too large, then the lens will be excessively mobile, which will lead to discomfort. The fit will be tight if the diameter is small - in this case, the edges of the lens will be in the limbus zone, which will lead to a violation of the blood supply to the cornea.

The size of the contact lens and the size of the cornea do not have to match

When developing the design and size of a contact lens, the size of the "universal" cornea of the eyes on which this contact lens will fit perfectly is calculated. When calculating the parameters of the "universal" cornea, the size of a huge number of corneas is taken into account, from which the arithmetic mean value is calculated.

That is why a contact lens with a universal size will fit most people. And this is the only reason why manufacturers do not produce contact lenses individually for each size of the cornea.

Some manufacturers, in addition to the standard lens size, specifically produce lenses for non-standard cornea sizes. But such corneas are the exception rather than the rule.

The radius of curvature is one of the important ones. We understand: what is the radius of curvature (base curvature) and how to measure it? Which lenses are right for you

Why define curvature and what it characterizes

What does it affect

How to choose a radius

Consequences of the wrong choice

How to know if your lenses are the right fit

How can you tell if the lenses are the right fit?

How to choose the right contact lenses?

How to determine the normal radius of curvature of contact lenses

What makes the right choice

The consequences of an incorrectly selected radius

Differences across brands

Categories

What to do if the product has already been purchased, but the parameter does not fit?

How to choose the right contact lenses

Video: How contact lenses are selected

What lens curvature radius is right for you

What is lens curvature and why is it needed?

How to choose the right curvature of contact lenses?

Main characteristics

optical power

Radius of curvature and diameter

Types of contact lenses

Oxygen permeability and moisture content

What threatens the wrong choice of lenses?

The value of the curvature of the lenses - how to choose

The concept of the radius of curvature

The consequences of an incorrectly chosen base curvature of the lens

Color contact lenses

DO YOU STILL THINK IT IS HARD TO GET CLEAR VISION BACK?

How is this parameter determined?

How important is the correct selection of this parameter?

What to do if the product has already been purchased, but the parameter does not fit?

What is the radius of curvature in contact lenses?

Why is it important to choose the right radius of curvature for contact lenses?

Contact lenses: how to choose the radius of curvature?

What else to look for when choosing optical products?

What can the radius of curvature of contact lenses affect?

How to determine the radius of curvature of contact lenses

How to choose the right radius of curvature for contact lenses

Determining the size of a contact lens

If the lens diameter is not correct

Determination of lens size using the example of Acuvue lenses