In the far-sighted eye, the length of the eyeball is too short in relation to the refractive media, meaning that the light rays that fall into the eye are refracted too little and form a focus that would theoretically lie behind the retina. The image on the retina is therefore blurry.
Eyeglass lenses for correcting farsightedness are called compound lenses (plus lenses).
A far-sighted person's prescription for glasses could be as follows:
Children can usually compensate for farsightedness with accommodation until young adulthood. As a result, the ciliary muscle in the eye is tense, the lens thickens and the refraction of light rays becomes stronger; this is known as “hidden farsightedness.”
The elasticity of the lens, i.e. the ability to accommodate, decreases slowly from school age until it reaches a minimum of around fifty. Depending on the severity of farsightedness, accommodation sooner or later in life is no longer sufficient to compensate for the defective vision and glasses are required.
From a certain age, people with hidden farsightedness often complain of headaches or even dizziness and nausea when reading or working closely; these symptoms are called asthenopic symptoms. They are triggered by the fact that the eyes constantly have to accommodate or the ciiary muscle is constantly tense. Relief glasses can help make vision more relaxed again, especially at short distances. Remote glasses may also be necessary later in life.
In cycloplegia, the ciiary muscle is paralyzed by special eye drops (cyclopentolate). Only then is a relaxed state in the eye achieved and the true extent of the visual defect can be measured.
Eye drops containing cyclopentolate dilate the pupil, which can cause glare. Accommodation is paralyzed, which causes nearby objects to be blurred. These effects usually subside after up to four hours, but can also last up to 24 hours. Children in particular can experience systemic “toxic” side effects, which usually subside after a few hours.
Adjusting relief glasses is usually not easy, as patients have become accustomed to correcting the visual defect with effort over the years. If the visual defect, which was measured in cycloplegia, were completely corrected from the start (e.g. sphere+2.5), there would be discomfort and the glasses would therefore not be worn consistently. For this reason, it makes more sense to correct only part of the hidden farsightedness (b.b.sphere +1.25) with relief glasses and then replace it later with a stronger correction.
Farsightedness can be corrected with eye laser up to a maximum of +4 dpt. If there is greater farsightedness, a PIOL (phake intraocular lens) can be used. Since far-sighted eyes are usually smaller than normal or short-sighted eyes, however, there is often not enough space to implant an artificial lens next to the natural one. In these cases, refractive lens replacement may be considered. The natural lens is replaced by an artificial lens, similar to conventional cataract surgery.
It is important that hidden farsightedness is discovered before an operation and that its extent is measured precisely.
