Lens diameter 14.2, can I wear 14.0? What ruler is used to change the cornea: how to find out the size of the eyes for lenses and the diameter of the products? Standard sizes of contact lenses for eyes

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

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

Determining your contact lens size

If the lens diameter is not selected correctly

If the diameter of the lens is not selected correctly, the lens will either fit loosely; 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 area, which will lead to disruption 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 ideally is calculated. When calculating the parameters of a “universal” cornea, the size of a huge number of corneas is taken into account, from which the arithmetic average is calculated.

This 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 of ​​the eye.

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

Determining lens size using Acuvue lenses as an example

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Inna 02/17/20

Hello! When checking, they said that a flat cornea and lenses are needed for 10.3, but such are not available. Is it possible to somehow correct the situation? Do the exercises? Drops? Previously, I could easily wear lenses, but now only for a radius of 9 and then no more than 2 hours, otherwise my eyes hurt a lot

Natalia Gusakova 08.11.19

Anastasia, hello! The choice of the size of the base curvature of the lens is possible only by assessing the fit of the lens on the cornea; lenses of different materials and different designs can fit completely differently even if they have similar sizes. Therefore, the choice of lens size is possible only in the contact correction office.

Anastasia 07/30/19

Hello. Please tell me. I wear daily lenses with a diameter of 14.3 and a radius of 8.5. I want to switch to two-week ones, what diameter do I need?

Natalia Gusakova 22.07.19

Hello, Alexander. The main criterion for selecting lenses is. Lenses with the same parameters but from different manufacturers will fit differently. The correct fit can only be determined by an ophthalmologist or optometrist in an optical salon.

Natalia Gusakova 22.07.19

Hello Igor. Standard lenses with a radius of curvature of 7.5 are not available. The only option is Concor lenses made to order; we do not cooperate with this company.

Igor 04/30/19

Hello. Tell me the possibility of purchasing contact lenses: +11 diopters, curvature 7.5

Alexander 03/30/19

Hello, I am currently using 1day acuvue trueye 8.5, 14.2 lenses. Will soflens daily disposable 8.6, 14.2 be suitable?

Natalia Gusakova 16.03.19

Karina, hello. To properly select toric lenses, it is necessary to evaluate the fit of the lens on the cornea. The main criterion for correct selection is a good fit of the lens on the cornea of ​​the eye.

Karina 03/02/19

Hello. I have astigmatism and it is difficult to choose lenses. According to the data, the radius of curvature is 8.6, the diameter is 14.5 large. But it’s impossible to choose. All presented toric (astigmatic) lenses with a diameter of 14.5 What to do?

Natalia Gusakova 26.11.18

Olga, hello! The selection of colored lenses is carried out according to the same parameters as regular lenses.

Olya 11/24/18

Hello. Is all this necessary for colored lenses?

Natalia Gusakova 23.04.18

Alexey, hello! The main indicator of correctly selected contact lenses is their fit on the cornea. The size of the lenses you have previously used is not the standard when choosing lenses of a different design and material.

Alexey 04/23/18

Good afternoon. I have been wearing since I bought my first pair of Ophthalmix 55uv lenses, radius 8.6, diameter 14.2 and -4.25 diopters. These lenses have now been discontinued. As can be seen from the above text, it is impossible to change the diameter of the lenses to a smaller or larger direction. Will you have to select from those available or can you vary it slightly by 0.1-0.2 mm?

Natalia Gusakova 18.03.18

Elena, hello! The diopters in contact lenses and the diopters corresponding to your visual acuity in spectacle correction differ due to the presence of the vertex distance (see the article "Vertex distance"). Therefore, diopters of -12.0 in contact lenses correspond to diopters of -14.0 with spectacle correction.

Elenka 03/18/18

Hello, I have glasses -15.0 and lenses -12.0 Acuvue Oasys. Should I increase the diopter of the lenses? If so, by how much to feel comfortable? Thank you.

Natalia Gusakova 12.03.18

Love, hello! It is not correct to recommend contact lenses based solely on refractometer data. The main indicator of correctly selected contact lenses is their correctness.

Love 03/10/18

Hello! Please tell me which lenses might be suitable? Weak small-scale nystagmus (almost imperceptible) Autorefractometer data: R 8.02/8.03, D 42.5/43.0

Alla 01/27/18

Good afternoon. My husband has -15.0; radius of curvature according to autorefractometer OD 7.29/7.25 OS 7.3/7.25. We can't find contact lenses for him. We tried lenses from different manufacturers, because... Lenses with standard parameters are not comfortable for him. Maybe this is due to its small radius? According to the autorefractometer data, tell me what radius you would recommend for him: 8.0; 8.2 or 8.4? Thank you in advance.

Natalia Gusakova 10.01.18

Victoria, hello! In addition to diameter, there are many other parameters that affect the fit of contact lenses, such as lens material, base curvature, and edge design. Different lenses have completely different parameters, but this does not mean at all that they will not suit you. Likewise, it does not mean that other lenses having the same parameters as your previous lenses will necessarily suit you. Therefore, the main criterion for correctly selected soft contact lenses is.

Victoria 01/08/18

Hello! Please tell me! I used to take lenses clarity 8.8 minus 3.25 and a diameter of 14.1, but now I can’t find one, they offer me a diameter of 14.2 or 14.5, tell me the diameter plays a role in the lenses? Thanks in advance!!!

Natalia Gusakova 15.12.17

Venus, hello! The principle of selecting colored contact lenses is the same as for regular lenses. If you take regular -5.25 lenses, then you need to take colored ones with the same diopters. But colored lenses with such diopter values ​​are only available from Alcon. By the way, these are safe silicone hydrogel lenses, unlike other colored lenses, which are hydrogel.

As for the size of the lenses, the only criterion for the correct choice of the size of any lenses is their correct fit on the cornea of ​​the eye and in no case is the criterion the size of the previous lenses, since lenses from different manufacturers or even different lenses from the same manufacturer will have different designs and consist of different materials, so if some lenses have a base curvature size of 8.4 and fit you well, then other lenses with other parameters will also fit well on the cornea with a size of 8.6 and a diameter of 14.2.

Therefore, the selection of lenses or the transition to lenses of a different design must be carried out in the doctor’s office, who will be able to assess the correct fit of the lens on the cornea; this will be the criterion for the correctly selected lens size. The only thing to consider when purchasing colored lenses is the possibility of a feeling of “fog” in the lenses due to narrowing of peripheral vision due to the pattern of colored lenses.

Venus 12/15/17

Good afternoon My daughter wears lenses with a radius of curvature of 8.4 in diameter 14.0 minus 5.25. But she really wants colored lenses, but with a radius there are only infinity lenses (Korea), we don’t want them, because... there the lens is completely colored, and therefore distorts color perception. Could you tell me: 1) are colored lenses different than colorless ones (different radius and diameter)?; 2) if -5.25, then you need - 5.50 with colored lenses. Thank you!

Natalia Gusakova 23.11.17

Daria, hello!

Acuvue 1 day TruEye and Acuvue Oasys lenses are different in design. The standard size for TruEye is 8.5, and the standard size for Oasys is 8.4. Therefore, the selection of TruEye lenses always begins with a base curvature size of 8.5 and only if they fit tightly on the cornea, size 9.0 is selected.

With Acuvue Oasys, you always start with size 8.4, no matter what base curvature your previous lenses had. The fit of the size 8.4 lens on the cornea is assessed and only if the Oasys size 8.4 fits snugly, size 8.8 or a different lens design (i.e., another brand) is selected.

Daria 11/23/17

Hello! Previously, I took 1-Day Acuvue Trueye -3.75 lenses with a curvature of 8.5. Now, to save money, I want to switch to 2-week lenses and chose Acuvue Oasys. But there the curvature is only 8.4 and 8.7. Which ones to choose?

Natalia Gusakova 30.08.17

Vitaly, hello! Comfort in lenses depends on many factors, including. Assessing the correct fit of the lens is an important point in choosing the lens size; without assessing the fit, it is not possible to say what size of the base curvature and lens diameter will be optimal for you. At the same time, lenses made of different materials having the same dimensions will fit completely differently on the cornea. Unpleasant sensations in the lenses can be not only due to improper fit, but also due to an inappropriate solution, with conjunctivitis, meibomitis, with.

Vitaly 08/28/17

Hello, I am being fitted for contact lenses and have been wearing them for 6 days. The left eye is almost used to it, but the right one feels like the wind is blowing into the eye. Lens parameters: radius of curvature 8.6 diameter 14.00 mm. I tried contact lenses with the same radius, but with a diameter of 14.1 mm, very unpleasant sensations in the eyes, a constant feeling of interference in the eye. Tell me, please, can a diameter of 13.8 mm be suitable for my right eye? Or what do you recommend? Best regards, Vitaly

Comfort, as well as the duration of wearing lenses, very often depends not so much on the level of production, but on the correct selection of products. Unfortunately, today only a few consumers know how to correctly determine the ideal soft optics for themselves and mistakenly rely only on diopter readings. In fact, proper selection of lenses includes many other parameters that affect the comfort of use. What these parameters are and how to choose lenses for the eyes according to them according to the recommendations of doctors will be discussed in this material.

Selection methods

Currently, the selection of soft lenses is carried out taking into account several characteristics of the patient’s eye, including:

• Corneal radius;
• Sagittal depth (a parameter depending on the sagittal (geometric) axis of the eye, which varies depending on the presence of certain pathologies, for example, in the myopic eye it is smaller);
• Chord diameter.

It is very difficult to measure these parameters for each eye, therefore the selection is carried out using the closest typical values. The basic formula for selecting lenses by sagittal size in this case is as follows:

For this formula:

• D – chord diameter;
• R – radius of curvature of the lens;
• A is the value of the sagittal size.

This selection method is used by almost all ophthalmologists, regardless of the optics manufacturer they use. To simplify the selection of lenses using this method, special tables are used. This technique is applicable for both soft and hard lenses and is universal for patients with various pathologies, including myopia, farsightedness or astigmatism. The procedure for selecting optics using such tables will be discussed below.

Measuring corneal diameter

This technique was originally proposed by the company engaged in the production of lenses “Bausch & Lomb”, in which ophthalmologists were asked to select optics for patients according to a table, focusing on the following patterns:

• Lens diameter 12.5 is recommended for corneal diameters less than 11.5 (which corresponds to the U, F series models for the proportion of patients suffering from myopia and N, H3 for farsightedness);
• Lens diameter 13.5 is recommended for corneal diameter 11.5-12.0 (corresponds to series for farsightedness B3, H3 or O3, U4 for myopia);
• 14.5 is the diameter of the optics, prescribed for corneal diameters greater than 12.0. Lenses of the B4, H4, O4, U4 series are suitable for it;
• If the patient has a large palpebral fissure, it is recommended to select samples of larger diameter;
• If you have a steep cornea of ​​45.0 D, it is recommended to take lenses of a smaller diameter.

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Below is the table for selecting lenses based on diameter:

Cornea diameter	Lens diameter	Series
for minus lenses:
from 11.5 to 12.0
for plus lenses:
from 11.5 to 12.0

This method is applicable to both patients with farsightedness and myopia. It makes it possible to select suitable samples that are closest in value, but in some cases it allows the production of special models to order.

Read also about contact lens addition in detail.

On measuring the corneal radius

This method is widely used primarily by the Cooper Vision company and is based on the following principles:

• When choosing optics, both the diameter and radius of the cornea are taken into account;
• They also focus on the mobility of the lens - in terms of choosing a more convex or flat analogue;
• Take into account the level of moisture in the eye;
• The size of the palpebral fissure is taken into account - the larger it is, the larger the diameter of the lens should be.

With this method, it is necessary that the diameter of the lens extends beyond the limb by 1 or 1.5 mm. This provides the most complete coverage of the viewing angle and gives the user maximum comfort while wearing the products.

On sagittal depth measurement

This method uses a study of the clinical refraction of the eye to obtain the most accurate lens selection parameters. It is suitable for working with Softcon optics. The choice of lenses in this technique is also based on the following principles:

• 8.4/14.0 lenses are recommended for patients with corneal radii of 41.25-42.0;
• Lenses 8.1/14.0 or 8.4/14.5 for corneal diameter 44.5-45;
• For a more accurate selection of samples, it is recommended to use the manufacturer’s tables for standard optics.

Since all of the above methods are focused on working with a typical set of lenses, they are not always productive for every patient. That is why doctors, when choosing soft optics, also focus on the thickness of the lens.

Read about how to choose contact lenses online.

Lens thickness

Focus on this parameter should take into account not only medical indicators, but also the patient’s convenience when working with thin optical samples. When selecting lenses by thickness, they are guided by the following indicators:

• Compliance with the anatomical features of the eye;
• Sample tolerance level;
• Eye tear level: if the level is low, it is recommended to use standard thickness of products, since ultra-thin analogues can dry out the mucous membrane;
• The presence of thickening of the iris, for example, after injuries and operations: in the presence of such a feature, the use of a lens of greater thickness is required.

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Trial set of soft lenses

It is not always possible to choose lenses the first time, even after taking into account all the details. In many cases, it is advisable to use a trial set of soft lenses. All soft optics manufacturers produce these today. The tables guide the specialist in choosing according to such parameters:

• Type of pathology (myopia, karatoconus, aphakia);
• Center thickness of lens;
• Lens refraction;
• Radius as well as width of the sliding zone;
• Radius of curvature of the rear optical surface.

The table itself for selecting trial soft lenses:

	Radius of curvature rear optical surface (mm)	Radius and width zones slip (mm)	Diameter lenses / diameter optical zones (mm)	Thickness lenses in the center (mm)	Lens refraction (D)
					5.0;-10,0;-15.0
					10.0:+14.0;+17.0
					10.0;+14.0;+17.0
Karatoconus		7.5×1.0 7.8 x 0.5 8.1 x 0.5 8.4 x 0.5 8.7 x 0.5
		7.9×1.5 8.4×1.0 8.9×0.5
		8.1 x1.5 8.6×1.0 9.1×1.0

These tables provide the fastest possible selection of lenses from the kit. The fitting of products from such sets is carried out as follows: the patient is put on lenses one by one, wait up to half an hour from the moment of fitting until lacrimation calms down and inflammation of the eye decreases, and after that they observe the nature of the fit of the lens, its mobility, as well as the appearance of discomfort while wearing it. .

Sometimes the structural features of an area of ​​the eye do not allow us to select a standard lens for it. If none of the standard shapes suits the client, it is recommended that lenses be made according to individual parameters.

Read about the rules for wearing contact lenses.

Violation of the position of the lens in the eye

In some cases, a lens selected according to certain parameters is incorrectly positioned in the eye. To resolve issues related to such problems, there is a special table that gives a list of universal recommendations for such problems:

Problem	Solution
Decentering the lens	Larger lens
Minimal mobility	Thicker soft contact lens, smaller diameter, larger base radius
Increased mobility	Thinner soft contact lens, larger diameter, smaller base radius
Discomfort	Larger soft contact lens, thinner lens, more hydrophilic
Low visual acuity	Thicker or chiseled lenses

They should be used as a guide when there is a need to quickly select the most adequate analog for the patient to wear optics comfortably.

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conclusions

As you can see, selecting lenses that are comfortable to wear all the time is a rather complex and painstaking task. It is almost impossible to carry it out without the help of specialists. However, if you go through all the necessary research and carefully follow the ophthalmologist’s recommendations, you will be able to choose high-quality products that are comfortable to wear. If you select it incorrectly, you can harm yourself and even develop dangerous diseases (for example, cataracts). may be ineffective.

You can choose the right contact optics only at an appointment with an ophthalmologist.

The doctor will check visual acuity with and without correction, perform refractometry, ophthalmometry, ophthalmoscopy, and biomicroscopy.

Determine yourself required parameters impossible.

What parameters are used to determine the size of contact lenses?

The size of contact optics determines two parameters: radius of curvature and diameter contact lenses, which are indicated on the package. They are measured using a special device - an autorefractometer.

Comfort depends on the first indicator when worn, as well as eye health. Essentially, the radius of curvature characterizes the curvature of the outer surface.

And the diameter depends on the size of the cornea and serves as a measure for determining the volume of a sphere, is responsible for the natural look and ease of use. When selecting optics, the following error occurs. Subjectively the patient believes that a tighter fit is more comfortable than a loose fit. On practice It is worth finding a middle ground so that complications do not arise.

It is believed that the lens did not fit correctly, if itching, burning and redness occurs eye. At the same time, factors that cause such symptoms are always excluded: damage, expired expiration date, non-compliance with hygiene rules.

Important! A common cause of such symptoms is individual reaction to the material.

In both cases it is required visit a doctor in order to find out the reason.

Lens radius of curvature: what is it?

This option characterizes the concavity of the inner surface. It comes standard and enlarged. The base size is considered to be from 8.3-8.7 mm. Suitable for most people with normal cornea structure.

Oversized radius sometimes exceeds 9.0 mm. The most convex product has a smaller radius. This fact determines correct landing.

To ensure comfort without visual distortion, the shape of the eyeball (cornea) and the curvature of the lens must follow each other's contours. If the shell has more rounded proportions Compared to the cornea (lens circumference is smaller), the fit will be steep. This leads to excessive tension in the blood vessels and redness of the eyes.

If the membrane has flatter characteristics(the lens circumference is larger), the contact optics become movable and the fit is flat. This causes constant friction, which leads to corneal inflammation and swelling. The procedure for determining the radius of curvature itself takes two minutes. It is carried out using computer technology and is painless.

How to find out the size of the cornea

Represents diameter of the cornea or convex transparent part eyeball. In appearance, it resembles a convex-concave lens of an aspherical shape. The vertical size of the cornea is smaller than the horizontal one.

Photo 1. Indicating the location of the cornea and its internal structure, consisting of several layers.

The diameter also varies and is about 10.00—10.56 mm. Adult size horizontally characterized by the magnitude 11.8 mm, vertical - 11 mm. Wherein radius of curvature normally does not exceed 7.8 mm. It also has a certain convexity coefficient.

What does lens diameter affect?

The location of the lens on the eyeball is determined by the diameter of the cornea. Selection correction means carried out according to a special table, which has a pattern: corneal diameter always less lens diameter by 1.00–1.50 mm. This feature provides convenience and comfort. When decentering the sphere, a larger diameter is selected. If there is immobility, it is reduced; if there is excessive displacement, it is increased. This helps relieve tension in the eyes.

Is the curvature of the product greater than the curvature of the cornea?

This option considered an individual value for every person. It depends on the features and shape of the cornea.

Because correction means vision are put on the cornea of ​​the eye, they must completely correspond to the natural form. With standard indicators of corneal curvature the required radius is considered to be r=8.6 mm.

Among the products of world brands you can find the best option for each person. In case of non-standard vision parameters, contact the manufacturers personally.

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Effect of material on lens fit

In addition to the basic lens size parameters, the quality of landing is influenced and the material from which the contact optics are made.

Important! Correct fit determined only by a doctor. As a result of self-selection, there are frequent cases of hypoxia, which leads to infectious diseases and keratitis.

Each composition hydrogel or silicone hydrogel, has a different fit with the same curvature. Hydrogel lenses are infused with a low-moisture gel. With the loss of the aqueous component, the dimensions of the contact optics themselves change, and the fit on the cornea becomes more dense.

Designed for convenience biocompatible technologies, the main advantage of which is the components, similar in composition to natural tear film. They prevent excess evaporation.

Silicone hydrogel have a breathable texture. The material contains siloxane, which has higher breathability coefficients. Despite the better fit compared to hydrogel, need extra hydration to ensure maximum comfort.

To determine the correct fit, a test is performed. To do this, the lens is moved up the cornea. If it freely returns to the central position, it means it fits the curvature parameters. Normal mobility is 1.5 mm. This is necessary to provide the eye with natural tears.

Standard sizes of contact lenses for eyes

To purchase contact lenses, it is not enough to know only the diopter value for both eyes. The diameter is sometimes different for the left and right organ of vision. And the base curvature is responsible for the quality of the fit and does not vary.

Standard parameters:

1. Diameter DIA= 13.5-14.5 mm in increments of 0.1.
2. Radius of curvature BC= 8.3-8.7 mm in increments of 0.1.

The main difficulty when selecting the size of contact optics becomes limited production according to the required parameters. Often brands do not fit any one of the measurements.

In any case, among a wide variety of products choose the right one, neglecting the advantages of moisture protection or breathability, which affects the wearing mode. This is especially true for people with an unusual eyeball structure.