Contact lenses – the importance of ophthalmological examination of people who use them
Contact lenses are optical aids that, like glasses, improve image quality and visual acuity in far-sighted, short-sighted people and people with astigmatism.
There are soft and semi-hard, ie. gas permeable (RGP) contact lenses.
Soft contact lenses are most often prescribed today.
They are comfortable to wear, easy to store and maintain. They are made of hydrogel or silicone hydrogel. They are stored in special solutions. They are larger than semi-hard lenses, so they are harder to lose sight of, which makes them especially suitable for sports activities. They can be with daily, biweekly and monthly replacement. With them, high diopters can be corrected, they enable much better image quality compared to glasses, they do not reduce the field of vision, they are aesthetically more acceptable because they are not visible to the eye. Soft lenses are more sensitive than RGP lenses, they are easily damaged (by nails), they are shorter, they are more expensive, infections are common in people who wear and maintain them inadequately, as well as allergic reactions.
If you wear them, in order for the diopter examination to be adequate, they must be removed the day before the examination!
RGP lenses are made of silicone acrylate.
They are smaller than soft lenses, they allow a good flow of tears between the eye and the lens, so they are said to be “healthier” for the eye. They are stronger, so it takes a period of getting used to wearing them, they move around the eye with each blink. Most RGP lenses are changed once a year, so they are much cheaper than soft ones. Eye infections are rare.
If you wear RGP contact lenses, in order to determine the new diopter as accurately as possible, you must take them off at least 15 days before the examination and not wear them in the meantime.
Each lens, whether soft or RGP, has its own specifics. These are the curvature of the lens (base curve – BC), the diameter of the lens (DIA), the strength (POW), the material from which the lens is made, the design (spherical, aspherical, conical…) and the like. There are also lenses that we prescribe less often, such as: Ortho K and scleral lenses.
Although they have many advantages over glasses, it should always be borne in mind that lenses are foreign bodies in the eye, they must be maintained properly, and every person who starts wearing contact lenses must go through training to put on, take off lenses and their proper maintenance. Each eye is special, depending on the curvature and size of the cornea, patients are recommended a different type of lens. Lenses are made in different sizes, from different materials, with different curvature, which must correspond to the measures of the cornea in order to avoid complications, among which the most common is corneal infection with consequent loss of vision. In order to prescribe the appropriate contact lens, it is necessary for the ophthalmologist to perform:
- Measurement of refraction by autokeratorefractometer
- Determining the best corrected visual acuity
- It is usually necessary to determine the diopter with dilated pupils, especially in children and young people
- Biomicroscopic examination
- Recording a topographic map of corneal curvature
- Measuring the amount of tears
Due to all the above, it is important to contact an ophthalmologist and not try lenses “on your own”. The diopter in the glasses often does not correspond to the diopter of the contact lens. An additional problem is often associated with associated eye diseases such as dry eye, chronic blepharitis, corneal and corneal scars, and it is therefore important to correct these conditions before prescribing contact lenses.
You should also know that some of the reactions to wearing lenses appear only after a few days or weeks.
In our office, you can do a detailed and quality ophthalmological examination and get the best advice on which type of lens is appropriate for you. We have trial sets of almost all registered manufacturers of both soft and RGP lenses.
Talk to us about which type of lens and diopter suits you best. See you!