Patients suffering from this condition have difficulty seeing objects at a distance; the picture is blurry and unclear. Nearsighted people can however see things up close. Similar to presbyopia , advanced nearsightedness is expressed in diopters, however with a negative symbol (i.e. -3 dpt).
Until recently it was said that it was better for light cases of nearsightedness to not wear glasses, so that “the eye would not become lazy but would work.” Today we see the error of such thinking – not correcting nearsightedness leads to other symptoms than unclear vision from afar (which in and of itself is sufficiently troublesome), but headaches, dizziness, disorientation, weaker vision at dusk and in the night. Constant rubbing and squinting can also cause tearing, burning, and even conjunctivitis. The current approach to treating nearsightedness recommends complete correction of the vision defect. It is proven, that not correcting or under correcting (correction using too weak of glasses) leads to faster digression of nearsightedness.
Nearsightedness, depending upon the degree of its advanced stage, is divided into:
- minor – also called “classroom” to -3D;
- medium – between -1D and -6D (according to some sources -3D to -8D),
- advanced – above -6D (according to some sources above -8D).
It is estimated that about 1.6 billion people in the world are nearsighted- by 2020 there will be 2.5 billion. This is one of the most prevalent vision defects.
Causes of nearsightedness
In an overwhelming number of cases, nearsightedness results from an ill formed eye. We distinguish between the following types of nearsightedness:
- Axial – it is caused by an enlarged eye ball and it increases with its elongation and stretching in the back pole of the sclera, choroid and retina. After birth, in the eyes of every child occurs the so-called physiological farsightedness (narrow light focuses on the retina), which with the lengthening of the eyeball slowly begins to lessen, to achieve regularity (emmetropization). Sometimes this process of lengthening the eyeball leads further to shortsightedness.
- Lenticular (curved) – causing an increased curvature (convexity) of the lens, its swelling, change of its refracting power.
- Corneal – results from a pronounced curvature of the cornea.
The most common occurrence of nearsightedness is axial, which grows gradually until the eye is fully formed (to about the age of 21). Accelerated growth arises during puberty. Usually this defect increases from .5 D to 1 D annually.
There are two more medical terms used related to this: school nearsightedness and refractive nearsightedness. The first is the slight nearsightedness that appears around 10-12 years of age and which may increase due to frequent accommodation tension and with extended vision usage up close- when a child reads frequently, studies, looks at the television screen, smart phone or computer. Refractive nearsightedness, in turn, is not related directly to the anatomy of the eye, but the coefficients of the refractive lens- a lens too strongly refracts the rays that it receives. Refractive shortsightedness may be the result of developing diabetes or cataracts.
Eye exercises for nearsighted people
Pronounced nearsightedness, often resulting from genetics, can often cause degenerative changes in the eye, so from the moment of the diagnosis, the patient should remain under the care of an ophthalmologist. At the outset when usually we are dealing with a lesser nearsightedness, the doctor can recommend varied exercises and change in lifestyle. In this context is included:
- Frequent time in fresh air- examination results show that 2-3 hours in fresh air daily cause a slowing effect on the development of nearsightedness. It is probably related to minimalizing the essential need to use accommodations, like squinting the pupil in clearer lighting (better, deeper image) with the direct effect of light exposure (freeing the retinal transmitter- dopamine, known as an inhibitor for the growth of the eyeball- in certain conditions). It does not matter the type of activity but the fact that they take place in the light of day.
- Compliance with hygienic visual rules: reading in a seated position, holding the text at a suitable distance, well-lit working place, good use of breaks during lengthy up-close work.
- Repeating several times a day exercises to relax accommodation, for example, comfortably gazing at a distant selected object for a few minutes.
How to diagnose nearsightedness?
After the initial interview with the optometrist or ophthalmologist, they will schedule a sciascopy and refractometry.
A sciascopy (retinoscopy)- this projects a narrow light beam on the bottom of the eye and observes the direction of movement of the red reflection from the bottom of the eye within the pupil. This exam utilizes special bars (lines) or the Hess circle imbedding in them different lenses of different power. In order to direct the exam, it is essential to use pharmacological immobilizing of the ciliary muscle responsible for adjusting the eye (accommodation).
Refractometry (“computerized vision exam”)- a computerized exam looking for refraction defects, in which is generally used a sciascopy. After the exam, a print copy is made with the values of the spherical defects (nearsightedness) and/or astigmatism.
Nearsightedness and astigmatism
Nearsightedness can be accompanied by astigmatism, which is a vision defect resulting in the eye’s inability to properly focus light rays upon the retina. Parallel light rays refract in two different places (i.e. vertical and horizontal), which causes an unclear image, which is curvy and wavy and with poor contrast. In the case where both defects combine, corrective glasses can be used with spherical-cylindrical lenses or toric contact lenses.
Approaches for nearsightedness correction
- Glasses and soft contact lenses: nearsighted people need concave contacts that correct negative or “minuses.” Glasses should be sufficient and adequate regarding the defect- deficient power is not recommended. An optometrist or ophthalmologist utilize glass with the minimal power, with which the patient can see optimally. Soft contact lenses give better correction for this condition in medium and pronounced values- they do not hinder the field of vision (with glasses one can only see directly ahead) and they don’t reduce the size of the object, which aids in the ease of: i.e. driving a car. There are scientific reports, that using soft contact lenses with children can slow down or stop the increase of nearsightedness. They observe that the pressure of the contact on the outer layers of the cornea causes flattening. Besides that, contact lenses affect the reduction of accommodation and also lower the pressure on the intraocular, which is one factor influencing the length of the eyeball.
- Orthokeratology/orthocorrection: involves the correction of nearsightedness with the aid of stiff, highly-permeable lenses with inverted geometry, used overnight. During this time, the lenses change the shape (flattening) of the frontal surface of the cornea, thanks to which you can see sharply without glasses during the day. The orthocorrection method may be used for farsightedness from 1D to 5D.
- Laser methods: people with a stable defect can undergo laser surgery. During the treatment for nearsightedness, an ophthalmic laser is used on the middle part of the cornea to flatten it and reduce the refractive power.
Vision correction lasers are used in the following procedures:
- LASEK/PRK method
- Trans-PRK smart surFace method
- LASIK method
- Femto-LASIK method
Lens surgical methods:
- Phakic lenses
- Replacement of refraction lenses
Phakic lenses (Visian ICL EVO+) are implanted upon the natural lenses. We correct pronounced vision defects > 8 diopters (nearsightedness) or when laser correction is not possible due to an overly thin cornea or the anatomical shape of the cornea does not allow a laser procedure.
Lens replacement, also known as refractive lens replacement, may be done by the use of various, individually matched lenses. In the treatment of presbyopia is used:
- Multifocal lenses from the newest generation (trifocal lenses to see close up and further into the medium distance field).
- Single focal lenses (monofocal) (also known as “strengthening lenses” are often used in cataract surgery).
- Toric lenses (for correcting astigmatism).
- Toric trifocal lenses (correct presbyopia and astigmatism).
- EDF lenses (extended depth of focus) through elevating the positive spherical values will allow good vision from a distance as well as medium ranged objects.