Refractive errors

Nearsightedness (myopia) is variously extended in the world, but there are considerable differences between ethnic and racial groups because hereditary factors play the central role. In the Western Europe and in the USA there is about 25% of individuals aged 12-54 years, who are shortsighted.

Hyperopia (farsightedness - hypermetropia) can be divided to axial or systemic according to the cause of the creation, ergo origin or in term of a connection to emmetropia.

Hyperopia (farsightedness, hypermetropia) is a refractive disorder, when light rays enter the eye, which is in accommodative composure. Light rays are refracted by an optical system and their focal point is created behind the retina. Due to this process, a fuzzy, blurred image of the observed object creates in the eye. This specific phenomenon can occur when reduced refraction of the eye optical system, particularly of cornea and lens in lesser extend (refractive hyperopia) and when the shortening of the aterodorsal lenght of the eye (axial hyperopia). In a large extend, hypermetropia depends on the lenght of the eye (axial hyperopia).

Nearsightedness (myopia) is the most common reffractive error, when rays of light entering the eye from a distance brake in front of the retina and blurred vision is creating on the retina. This specific event can occur when:

Many presbyopic patients, especially those who are not accustomed to wearing eyeglasses, are interested in contact lens correction of their refractive error. There are a variety of ways to correct presbyopia with contact lenses. Each of these options has advantages and disadvantages. The patient is individual priorities and visual demands can help decide which option to pursue.

The current generation of active living people over the age of 40-45 years - the so-called "baby boomers" - is very large group of populations. These people are at an age when their economic situation allows them to actively play sports, travel or pursue hobbies and passions. But it is also a generation that does not want their age in some way to reveal and emphasize but the opposite.

Ways of presbyopia correction using monovision has certain advantages, but of course also has many disadvantages and limitations. It could cause in certain activities serious problem, therefore monovision is not suitable for everyone and for all activities.

The method monovision is way of presbyopia correction, when is corrected differently each eye. One is corrected for distance and one for near. This correction can be done in three different ways. The most commonly used method of correction is using single-vision contact lenses.

Ways of presbyopia correction using monovision has certain advantages, but of course also has many disadvantages and limitations. It could cause in certain activities serious problem, therefore monovision is not suitable for everyone and for all activities.

When it becomes a problem with presbyopia, and if the patient has good binocular vision, it is possible to offer him in one eye corrected for distance and the other eye corrected for near. This method of correction of presbyopia is called monovision.

Astigmatism is a common type of refractive error. It is a condition in which the human eye does not focus light evenly onto the retina, the light-sensitive tissue at the back of the eye. Astigmatism in the eye means that the cornea is oval like a football instead of spherical like a basketball. Most astigmatic corneas have two curves – a steeper curve and a flatter curve. This causes light to focus on more than one point in the eye, resulting in blurred vision at distance or near. Astigmatism often occurs along with myopia or hypermetropia.

Presbyopia is a disorder caused by physiological aging of the intraocular lens. The eye lens gradually loses its plasticity and elasticity, its core gets larger and denser, its lens fibers sclerotize, the lens gains some volume and this leads to gradual diminishment of the accommodation ability which is irreversible.

There are many old and new theories which try to explain the causes of shortsightedness (myopia). In spite of significant scientific effort even now we are not hundred percent sure what is the exact cause behind it. The emphasis is put on various factors such as disproportions in the development and growth of the eye, inferiority of the optic tissue (mainly the sclera), infectious diseases, improper nourishment, excessive eye strain, insufficient illumination but mainly heredity. However, this definitely is not a complete list of possible causes of myopia.

It is not easy to put yourself into the shoes of person with myopia (nearsightedness) and understand his problems. It is true also for experienced ophthalmologist or optometrist. Every person with myopia certainly remembers the precise moment when he found out that he did not see objects at the distance as well as other people. This discovery accompanies him during his whole life. Then his life more or less differs from lives of those who do not suffer from this refractive error depending on the degree of his shortsightedness (myopia). He must accommodate himself to this situation every day, during his whole life. It can bring about stress, higher life expenses (eyeglasses, contact lenses) and inability to exercise some occupations, sometimes even early disability or disharmony in personal life.

Refractive errors can be simply divided to low and high. In high errors, vision is substantially worse, blurry and inaccurate. The eye itself is not capable of correcting such an error and therefore does not even try to do it. This error begins and ends with worse vision and it is not problematic to discover it.

At the moment the cause of night myopia (nocturnal myopia) is not entirely known. It is caused to some degree by spherical aberration (due to wide pupil in the dark environment), chromatic aberration (due to large share of short-wave blue green part of the spectrum at dusk) and mental causes - excessive accommodation to compensate for blurry vision.

The correction and treatment of presbyopia must be handled individually. The amount of accommodation varies not only from person to person but also from eye to eye. Therefore it is necessary to prescribe the weakest lenses which are tolerable for good and comfortable vision in order to find the harmony between the processes of accommodation and convergence. In the case of correction it is necessary to respect working distance to which a person has to adapt its vision and which is very important in various professions.

Farsightedness ( hyperopia, hypermetropia) can be corrected by prescription eyeglasses, contact lenses and increased using of surgery majors nowadays, although it still does not achieve the same number compared with the surgical solution of myopia.

Farsightedness (hypermetropia or hyperopia) is the most missed eye condition at school and pediatrician screenings because small to moderate amounts don't usually blur the child's vision. Children's symptoms increase with age and amount of hyperopia, but they often don't know that the discomfort they feel is abnormal and they get numb to it. Often, it plays out as near-task avoidance.

Hypermetropic eye tends to constantly acommodate perfectly. Low degree of the disorder is usually performed in childhood and younger ages imperceptibly due to their large accommodative width. Their accommodative reserve is sufficiently large and they correct the disorder with their own accommodative effort. Simply said, the eye helps itself without using a corrective widget.