Contact lens curvature radius

Hereditary diseases, unhealthy lifestyles, stress, prolonged sitting in front of the monitor screen can impose their negative prints on the quality of vision. Therefore, over time, many have to use assistive devices to ensure high-quality vision - glasses or contact lenses. Due to the peculiar way of life, wearing glasses is not suitable for everyone.

For example, athletes, actors, circus artists, diesel locomotive drivers, due to the nature of their work, cannot afford to wear glasses. Yes, and modern people who primarily value comfort and freedom of action in everyday life make their choice in favor of contact lenses.

What is the radius of curvature in contact lenses

This concept refers to the ratio of the radius of the inner surface of the lens to the outer diameter of the lens. This numerical designation is used so that the lens, when fixed to the eyeball, repeats its outline as clearly as possible. Indeed, otherwise, with daily use of the lenses, uncomfortable sensations, irritation of the surface of the cornea of ​​the eye, and even the occurrence of various diseases can occur.

On individual packaging, this is indicated by BS or BC. In addition, contact lenses with a correctly selected radius of curvature provide a clearer image, which is characterized as the optical power of the lens. It depends on the radius of curvature of the outer and inner surfaces of the lens and the refractive index of the material used.

How to determine the radius of curvature in contact lenses

The radius of curvature of contact lenses in each case is selected individually. An ophthalmologist uses autorefractometry to individually and more densely fix the lens to the surface of the eyeball. Based on the result, the ophthalmologist can determine the need for the use of certain lenses.

Did you know: having an identical radius of curvature, contact lenses from different manufacturers have varying degrees of fit on the eyeball.

Therefore, it is not enough to know only your radius of curvature when acquiring contact lenses. When buying in optical stores, you must also indicate the manufacturer whose contact lenses you wore recently.

Curvature Radius Table

Kerato cone stageThe central radius of the cornea, mmR0 mmR0-R1, mmR2-R1, mmDiameter of the optical zone, mmKL diameter, mmThe width of the peripheral zone, mm
17,2 - 7,07,25 - 7,00,5 - 0,80,8 - 1,24,5 - 7,09,2 - 9,50,7 - 1,2
27,0 -6,757,1 - 6,75 0,5 - 0,70,7- 1,24,5 - 7,09,2 - 9,50,7 - 1,2
36,7 - 6,06,8 - 6,00,4- 0,60,7 -1,24,5 - 7,09,2 - 9,50,7 - 1,2
46,0 - 5,06,1 - 5,00,4- 0,60,6 - 1,24,5 - 7,09,2 - 9,50,7 - 1,2

Where R0 is the radius of the optical zone, R1 - radius of the slip zone, R2 - radius of the peripheral curvature of contact lenses.

Individual selection of the radius of curvature of the lens is determined by the doctor

It should be understood that there are numerical expressions of the radius of curvature that are used most often. But even among ophthalmologists there is no such thing as a standard size.

The size and radius of the main apple for each person is purely individual, so the correct selection of contact lenses is carried out strictly according to individual parameters.

It is worth noting that the most popular lenses with indicators from 8,3 before 8,8 They are sold in optical stores all the time, but deviation, both up and down, may require an individual order.

The effect of the radius of curvature of contact lenses on vision

Incorrectly selected lenses can contribute to the development of discomfort during prolonged wear, fuzzy display of the contour of surrounding objects and the development of diseases. The too tight fixation of the lens on the surface of the eyeball almost completely blocks the access of oxygen to the cornea of ​​the eye.

In addition, the exchange and abduction of tears in the space between the cornea and the contact lens is significantly impaired. This situation is dangerous in that the disturbed metabolism does not manifest itself in any way until a critical situation arises due to the fact that the cornea of ​​the eye does not have pain receptors, which leads to corneal hypoxia.

To prevent such a case, it is recommended to use special lenses based on silicone and hydrogel, where silicone is responsible for the access of air to the cornea directly from the atmosphere, and hydrogel for the compatibility of the structure of the lens and eyeball tissue.

Important information: Daily use of silicone-hydrogel contact lenses is by far the most appropriate option for vision correction.

In the opposite case, the installation of lenses with an incorrect radius of curvature to the larger side will lead to such a situation when the lens on the surface of the eyeball is not sufficiently fixed.

This causes a lens shift during blinking and severe irritation. With this improper selection, patients often complain of the entry of small grains of dust or sand into the space between the cornea and the lens, which contribute to severe irritation.

Of course, for a high-quality selection of contact lenses, it is simply necessary to know your radius of curvature. However, a clear understanding is required that only a professional specialist can choose the most correct choice of contact lenses.

Watch the video: Anatomy of a Contact Lens (March 2024).

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