What is the radius of curvature of the lens? How to calculate it correctly? This question is asked by every person who decides to wear contact lenses for vision correction and goes to them for optics. The exact answer to this question can only be given by a professional ophthalmologist. If the radius of curvature of the lens is chosen incorrectly, you risk not only not improving vision, but also worsening it. Your eyes will be uncomfortable, they will experience stress, and you - constant inconvenience.
The radius of curvature of the lens, which is suitable for a particular person, depends on the structure of his eyeball. The lens is put on the cornea of the eye, and therefore should most accurately repeat its shape. The standard sizes of the eyeball have approximately the following indicators:
the length of the optical axis is 24 mm,
the length of the eye equator is 23.6 mm,
and the vertical diameter is 23.4 mm.
For a person with such standard indicators, the desired radius of curvature of the lens is 8.6. Lenses with indicators from 8.3 to 8.8 are easy to find on the open market. With a significant deviation from the average norm, you need to look for the manufacturer that makes contact lenses on order. In this case, it is necessary to draw up a sketch of the desired lens in an internal consultation with an ophthalmologist.
How does a doctor determine the appropriate radius of curvature of the lens? To do this, there is a special method called autorefractometry. An optometrist examines the cornea using computer diagnostic methods. The procedure takes only a few minutes. The method of autorefractometry is based on the principle of infrared light emission by a device. Sensors capture the image of a beam of light before it is reflected from and after the retina. Retinal research results provide a lot of useful information for a person about to buy lenses. The radius of curvature is only one of the indicators, the procedure also gives an idea of the difference in refraction observed between the eyes, and determines the magnitude of astigmatism. An infinitely distant image is used as the fixation point.
What to do if the lenses are already purchased, and the radius of curvature of the lens does not suit you? If the difference does not exceed 0.2, then doctors advise to try on the lenses and wear them if the discomfort is not noticeable. Often the lenses of one manufacturer with a radius of curvature of 8.5 correspond to the lenses of another manufacturer with a radius of 8.6. If the deviations exceed 0.2, then such contact lenses should not be worn in any case!
What are the symptoms and inconveniences of people who wear lenses that are not suitable for them? If a person puts on a more convex lens than is required by the structure of his eye, then the mobility of such a lens will be difficult. The eyeball will be in constant tension, the blood vessels will be squeezed, which will inevitably lead to redness of the entire eye. A violation of tear exchange is possible, since tears cannot pass through the lens closely adjacent to the cornea. The threat of inflammatory diseases will increase, and vision will become unstable. If, on the contrary, the radius of curvature of the lens is greater than the desired indicator, the lens will be too mobile. It can easily fall out of the eye or cause tearing, harm the cornea. A flat lens will easily move away from the cornea and you will see almost nothing. It will be painful for you to blink, since the lens will touch the upper muscles of the eye, and each time a fine grain of sand or a speck of eye gets into the eye, it will itch and blush.
Together with the ophthalmologist, select the appropriate radius of curvature of the lens and look at the world with wide eyes! Myopia and farsightedness are not reasons to refuse to enjoy all the colors and colors of life. Get contact lenses that will be convenient for you.