Definition
Astigmatism is one of the three basic visual impairments, in addition to myopia and hyperopia. It often coexists with these defects. Astigmatism is the irregular refraction of light by the cornea or lens of the eye in different sections of the eyeball.

The most common cause of astigmatism is the uneven curvature of the cornea. In a healthy eye, the cornea is spherical (like a volleyball), while in an astigmatism eye, the cornea is more oval (like a rugby ball). This condition causes the ray that passes through the cornea, instead of at one point, to focus in two different planes.

Symptoms
Astigmatism is a common disadvantage, but not all patients suffer from it. It is estimated that an astigmatism of 0.5 D has 75% of patients who come for glasses. In a situation where the defect is small, the compensating mechanism is able to make up for the deficiencies and ensure correct vision, but after prolonged visual work, the patient feels discomfort. People with astigmatism complain of blurry or distorted vision of objects both far and near. In addition, this uncorrected defect causes frequent headaches, a burning sensation, and eye fatigue.

Causes
Most often, the defect is congenital. Many factors, affecting the cornea and lens of the eye, can cause acquired astigmatism (most often cuts, inflammations, eye operations). The aggravation of the defect is favored by age and the changes in the structure of the eye that occur with it.

Treatment

• Prescription glasses

Regular astigmatism is usually corrected with cylindrical lenses. The eyeglass lenses used in astigmatism have an appropriate structure (two different powers) so that all the light rays that enter the eye are focused on the retina.

In the case of severe astigmatism or irregular astigmatism, correction with glasses does not give the desired effect. Modern ophthalmology is still looking for solutions and improving the already existing methods of treatment that will not only allow you to resign from glasses, but also significantly improve the quality of vision. People who are intolerant of glasses for various reasons can be offered:

• Contact lenses, individually selected for a given patient.
• Laser refractive treatments.
• Surgery:

• • performed simultaneously with cataract surgery:
    • toric implant of the AcrySof TORIC intraocular lens,
    •  LRI limbal relaxation incisions.
  • implantation of a toric phakic lens,
  • astigmatic keratotomy.

DEFINITION

Short-sightedness, from the Greek myopia, is one of the most common refractive eye defects. In a normal (regular) eye, a beam of light rays falling parallel to the eye is focused on the retina. In myopia, in a non-accommodative eye, the light rays that enter the eye focus in front of the retina and then diverge again, producing a blurred, blurred image on the retina.

Objects far from the eye are not seen clearly or are perceived as distorted. Close-up vision may be correct in minor defects. The size of myopia is measured in diopters.

CAUSES

There are three causes of myopia.

The most common cause is excessive length of the eyeball axis. This type of nearsightedness is known as axial myopia. It is associated with the excessive growth of the eye. It usually develops during puberty and reaches its final level between the ages of 15 and 30.

Nearsightedness can also be caused by too high breaking force of the optical system elements of the eye. The reason for this phenomenon is too convex curvature, most often the cornea, less often the lens (curvature myopia) or too high refractive index in the eye lens. The latter type is referred to as refractive myopia and is most common in diabetes or nuclear cataract.

Most often, myopia is diagnosed in school-age children (between 8-12 years of age). During adolescence, when there is a rapid growth, the size of the visual defect increases. At the age of 20-40, the defect most often changes slightly. Hereditary factors and frequent repetition of activities that require looking closely for a long time (e.g. reading, working on a computer) play a large role in the disclosure of myopia. In women who are predisposed to this vision defect, pregnancy is a factor that may contribute to its worsening.

DEGREES OF SHORT SIGHT

There are several degrees of myopia. The higher the degree, the more blurred objects away from the eye. There are four degrees of myopia:

• Low myopia down to -3.0 diopters – usually occurs around the age of 10 and stabilizes with the cessation of eye growth, i.e. around the age of 20. With the defect of –3.0 diopter, close-up vision is even comfortable, because it does not require accommodation.
• Mean myopia of -3.0 to -6.0 diopters usually begins earlier in life.
• Nearsightedness high above -7 diopters often occurs in early childhood. High myopia is not just a refractive error that can be fully corrected optically. With high myopia, degenerative changes in the choroid, retina and vitreous can occur later in life. There is an increased risk of a retinal detachment. Changes in the eye structures can permanently impair vision.

FREQUENCY

Nearsightedness is the most common refractive error of the eye. In adults, myopia is manifested on average, as in the third patient. In Asians, it occurs twice as often as in Europeans, while it is less common in Melanesia and Polynesia. The deterioration of the visual impairment is undoubtedly influenced by environmental factors, mainly excessive visual work from close distances. The number of myopia patients increases with the development of civilization, e.g. within 10 years the number of children with myopia in the USA has doubled.

SYMPTOMS

People with this defect can clearly see objects in close proximity, while distant objects are out of focus. Short-sighted eyesight, in order to see sharper, moves the object closer to the eyes or moves closer to the object, e.g. to a TV set. He also often blinks his eyes, thanks to which he cuts the so-called Image “scattering circles” on the retina, thereby increasing the depth of field. The name for myopia comes from the Greek (myopia = squint).

TREATMENT

• Spectacle correction

The most commonly used method of compensating for typical refractive errors such as e.g. myopia is corrected with glasses. For myopia correction, spherical, concave, negative power lenses are used. They extend the focal length of the eye’s lens and thus shift the point of focus of the rays backwards, thanks to which the rays focus on the retina. Unfortunately, due to the distance of the eyeglass lens from the eye by an average of 12 mm, the image formed on the retina is reduced in relation to the reality.

• Contact lenses

In recent years, this method of correction has gained more and more supporters and has many advantages. Currently, there is a large selection of contact lenses available, which should be selected by the doctor depending on the vision defect and the structure of the eye. It is unacceptable to buy them without prior selection by an ophthalmologist, as too tight or too loose lenses can cause serious, irreversible damage to the eye. The lens power also differs from the eyepiece power because in both methods the location of the correction is at a different distance from the retina.

•  Surgical correction of myopia

Refractive surgery is a new direction in ophthalmic microsurgery aimed at reducing or completely independent of people with visual impairment from glasses or contact lenses. There are many surgical treatments for visual impairment. These procedures are not performed due to emergency or other medical indications, but only at the patient’s request. Be aware that, like any other surgical procedure, these procedures come with potential risks. Despite the highest level of performance of the procedure and postoperative care, complications may occur, which may, although rarely, even cause visual deterioration. Two groups of treatments can be distinguished: one based on the cornea and one based on the eye lens.

CORNEAL TREATMENTS

They correct the vision defect by surgically changing the curvature of the cornea in the central part. Corneal procedures do not require opening the inside of the eye, as in the case of procedures performed on the lens. There are several methods of carrying out the procedure:

• making radial incisions in the cornea (radial keratotomy)
• modeling the appropriate curvature of the cornea using an excimer laser (PRK, LASIK, LASEK, epi-LASIK)

Radial keratotomy (RK) was a popular method in the 1970s, consisting in making several deep incisions in the cornea (up to 95% of its thickness) radiating around the pupil in order to change its focus strength of light rays. During healing, the cornea flattens, so this method is only suitable for nearsighted people (-2 to -8 diopters) and people with myopic astigmatism. The outcome of the operation depends largely on the experience and precision of the ophthalmologist who makes incisions by hand. The disadvantage of the method is the healing period of several days. About 10 to 30% of patients after surgery still need glasses (only weaker glasses) to see really sharply. Often, several years after the procedure, the patient has to wear glasses again, this time for near vision, because the incised cornea flattens too much over time, leading to farsightedness. Some patients also complain about the deterioration of visual acuity with the passage of the day. RK is the cheapest and the most risky procedure to correct myopia, which is why this method is abandoned in Poland, as well as in the world.

LASER PROCEDURES

Currently, the most frequently used refractive surgery procedures are procedures using the excimer laser – PRK and LASIK, consisting in changing the curvature of the cornea. The excimer laser (excited dimer) produces a cold, pulsed ultraviolet beam with a wavelength of 193 nono meters, and with each pulse the laser breaks the molecular junctions of the corneal cells with an accuracy of 0.25 microns. Often, only the removal of 50 microns of corneal tissue (about the thickness of a hair) is sufficient to obtain the correct amount of vision correction. An additional advantage of the excimer laser is the emission of cold light, which does not burn the corneal tissue.

PRK (photo – refractive keratectomy) is a treatment on the cornea, the aim of which is to properly model the central surface of the cornea with a laser beam so that it focuses the image precisely on the surface of the retina. Removal of a thin layer of corneal tissue allows it to flatten or emphasize it and change the focusing force of the entire optical system of the eye.

Surgical technique: Immediately before the procedure, after anesthesia of the eye, the corneal epithelium is removed mechanically and the excimer laser acts on its deeper layers. After the procedure, the eye must be protected with a dressing and the patient may feel a little pain. However, in 10-20% of patients the pain may persist for several weeks. Since the corneal epithelium has to regenerate completely, the final shape of the cornea is established after about half a year and only then can the effects of the treatment be fully assessed. Quite often, mainly in patients with a large defect, there is a risk that the cornea will take a different shape from the intended shape during healing, which may lead to, for example, astigmatism that is difficult to correct over time.

A significant improvement in visual acuity occurs immediately after the procedure, but complete stabilization is achieved after a few weeks. Using the PRK method, we can correct myopia from -1.0 to -8.0 diopters. The effectiveness reaches 95% -98%, but in the case of larger defects it significantly decreases. The PRK method cannot operate on both eyes at the same time and a three-month break is necessary.

LASIK (laser assisted in situ keratomileusis) is a technique whose aim is to model the surface of the cornea so that it can properly focus the image on the retina. LASIK is a two-phase procedure. In the first step, a thin, superficial corneal flap is cut off mechanically (with a special instrument called a microkeratome) or laser. This petal is turned sideways (like the lid of a canned food). In the second stage, the excimer laser beam precisely models the exposed surface of the cornea. At the end of the procedure, the superficial corneal flap is put back in place.

The LASIK method allowed for the extension of the power range of the corrected defects. Rehabilitation is the fastest in this method. In the postoperative period, the patient feels no pain, only mild discomfort that lasts for several hours. He is not forced to wear a bandage, which allows both eyes to be operated on at the same time. With this technique, the recovery period usually lasts several days, unlike PRK, where this period may take several weeks. The treatment allows you to correct defects with the power of -10.0 to +6.0 diopters. With high defects, laser procedures are not recommended because they cause complications: poor vision quality, defect regressions and others.

The disadvantage of all the methods described is their irreversibility. If something goes wrong, it’s hard to fix. All laser procedures (PRK, LASIK) are performed on an outpatient basis under local anesthesia. However, they are subject to strict surgical procedures.

Contraindications to laser vision correction are:

• age under 21
• no defect stabilization
• additional eye diseases (glaucoma, cataracts, retinal detachment, eye inflammation, keratoconus and corneal changes, dry eye syndrome)
• diabetes
• connective tissue diseases (so-called collagenoses) – e.g. rheumatoid arthritis, scleroderma, lupus, polyarteritis nodosa, psoriasis, Sjogren’s syndrome
• autoimmune diseases
• diseases with the weakening of the body’s immunity
• atopy and severe allergies
• active infectious diseases
• the individual’s tendency to form overgrown scars, called keloids
• implanted pacemaker
• pregnancy and breastfeeding.

Before laser vision correction surgery, you must not:

• I wear soft contact lenses for 3 weeks and hard contact lenses for 4 weeks
• consume alcoholic beverages at least 48 hours before the correction
• use cosmetics and perfumes 24 hours before surgery
• Oral contraceptives are recommended for use in women
• a period of 3 months before and after the procedure.

LENS TREATMENTS

Refractive RLE lens replacement

This method is an intraocular method involving the removal of the patient’s own, often healthy, lens and implantation of an artificial lens in its place. The procedure is performed under local anesthesia and, similarly to cataract surgery, the patient’s lens is replaced with an implant. Until recently, the disadvantage of this method was that the artificial lens does not have the ability to accommodate (adapting to acute vision both near and far). This method is therefore mainly recommended for patients with myopia after the age of 50 and for those who have corneal problems and the onset of cataracts. In recent years, the market of intraocular implants has been developing more and more dynamically and multifocal lenses and accommodating lenses are already being produced. These treatments are associated with an increased risk of retinal detachment.

Phakic lenses

In this method, an artificial lens is also placed inside the eye. In the case of a phakic lens, however, the own lens is not removed, but the eye implant is attached to the eye with a translucent natural lens. Phakic lenses are often compared to contact lenses, which, instead of being placed on the surface of the eye, are permanently implanted inside the eye. The material of the phakic lens is similar to that used in lenses used in cataract surgery. Phakic lenses are designed to correct myopia from -5.0 to -23.5 diopters. During the procedure, it is possible to correct astigmatism at the same time. Artisan / Artiflex lenses used in our center are implanted into the anterior chamber and fixed on the iris. Cache’t lenses placed in the anterior chamber of the eye are also available. The advantage of this method is that it is reversible.

DEFINITION

Farsightedness (popularly known as farsightedness) is a refractive eye defect. In a normal (regular) eye, a beam of parallel rays entering the eye is focused on the retina. In hyperopia, in the non-modulating eye, the optical rays refract instead of on the retina, outside of it, which causes the image to become blurry.

In order to clearly see a distant object, the farsighted viewer must accommodate. Accommodation involves tensing the eye muscles, which changes the optical strength of the lens. The contraction of the eye muscle around the equator of the lens releases the tension in the ligaments that strain the lens, thickening the lens and increasing its refractive power. We usually need accommodation to sharpen our vision when we shift our eyesight from far to close.

The amount of hyperopia is measured in diopters. The extent of acute vision depends on the size of the defect and the amplitude of accommodation, which decreases with age.

FREQUENCY

Farsightedness is the second most common refractive defect of the human eye, after myopia. It is estimated that 50-60% of the population is hyperopic. Most often, the disease manifests itself already in childhood, although it may survive for many years in a latent form and reveal itself when the processes related to the aging of the eye begin. Around the age of 40, the mechanisms of accommodation weaken. With age, the refractive index of the eye’s optical centers (mainly the cornea and the vitreous body) gradually decreases. Presbyopia makes it necessary to increase the power of lenses for near and far distance.

CAUSES

Farsightedness is most often genetically determined. The disease most often manifests itself in childhood.

The cause of hyperopia is too short antero-posterior axis of the eyeball, axial hyperopia or too flat curvature of the cornea.

Physiological hyperopia occurs in young children because their eyeballs are short. As you age, your eyeballs grow like your entire body. The greatest hyperopia occurs in children under 3 years of age, because their eyeballs are much smaller than in adults. On the other hand, children and adolescents have a very high accommodation capacity, caused by the flexibility of the lens, which allows them to compensate for small defects. The child has such a strong accommodation that he can even compensate for hyperopia of the order of 7 diopters when looking into the distance.

SYMPTOMS

The hyper-sighted eye can see objects both distant from the eye and those located in close proximity in a blurry distance, but with a small degree of defect, the accommodation mechanism is able to compensate for the visual defect, which allows correct vision. However, it requires a huge accommodative effort and is only possible in children and adolescents. Due to the ease of increasing the optical power of the eye thanks to accommodation, children suffer from latent hyperopia, and at an early age the defect is only partially revealed. Chronic accommodation tension may induce permanent contraction of the eye muscle. Such a condition causes pain in the eyes and head, and the permanently thickened lens increases the optical power of the eye and paradoxically simulates myopia. In the event of inaccurate examination of the eye, this may lead to incorrect, negative correction.

In major defects, or when the natural focusing ability of the lens gradually declines with age, hyperopia prevents you from seeing objects clearly both near and far. Since the eye needs stronger accommodation when looking at close-ups, the farsighted viewer sees a blurry image, especially when reading or working at the computer for a long time, and when the eye is tired. The uncompensated defect can cause headaches and irritation of the conjunctiva. Uncorrected hyperopia and the associated constant tension of accommodation can lead to disturbances in the entire muscular system of the eye, including accommodative strabismus.

TREATMENT

In order to carefully examine the size of the defect, children and adolescents require complete, pharmacological paralysis of accommodation. The strongest revocation of accommodation occurs after the use of atropine drops. The palsy of accommodation after atropine lasts up to two weeks, during which it is difficult to see precisely at close range, including reading.

In some cases, especially in older adolescents, in the absence of strabismus or suspected accommodation spasm, the doctor may decide to cancel it with other, shorter-acting pharmacological agents.

Spectacle correction

The most commonly used method of compensating for typical refractive errors such as e.g. myopia is corrected with glasses. For the correction of vision in hyperopia, spherical converging lenses with positive power are used. They are thicker in the center and thinner around the circumference. They shorten the focal length of the eye’s lens and thus shift the focal point of the rays forward, making the rays focus on the retina. Due to the distance of the eyeglass lens from the eye by an average of 12 mm, the image formed on the retina is enlarged in relation to the reality.

Contact lenses

In recent years, this method of correction has gained more and more supporters and has many advantages. Currently, there is a large selection of contact lenses available, which should be selected by the doctor depending on the vision defect and the structure of the eye. Each lens has a different radius of curvature and diameter and must be individually fitted to the patient’s eye. It is unacceptable to buy them without prior selection by an ophthalmologist, as too tight or too loose lenses can cause serious, irreversible damage to the eye. The lens power also differs from the eyepiece power because in both methods the location of the correction is at a different distance from the retina.

Surgical correction of hyperopia

Refractive surgery is a new direction in ophthalmic microsurgery. This method does not heal the eye, but aims to reduce or completely make people with visual impairments independent of glasses or contact lenses. There are many surgical treatments for visual impairment. These procedures are usually not performed due to medical indications, but only at the patient’s request. Be aware that, like any other surgical procedure, these procedures come with potential risks. Despite the highest level of performance of the procedure and postoperative care, complications can occur, which may, although fortunately rarely, even cause vision deterioration. Two groups of treatments can be distinguished: one based on the cornea and one based on the eye lens.

CORNEAL TREATMENTS

They correct the vision defect by surgically changing the curvature of the cornea in the central part. Corneal procedures do not require opening the inside of the eye, as in the case of procedures performed on the lens. There are several methods of carrying out the procedure:

• making radial incisions in the cornea (radial keratotomy)
• modeling the appropriate curvature of the cornea using an excimer laser (PRK, LASIK, LASEK, epi-LASIK) 

Radial keratotomy (RK) was a popular method in the 1970s. The procedure involves making several deep incisions in the cornea (up to 95% of its thickness) radiating around the pupil and is aimed at changing the focusing force of light rays. During healing, the cornea becomes more prominent in the center. This method is best suited for the correction of myopia and short-sighted astigmatism. The outcome of the operation depends largely on the experience and precision of the ophthalmologist who makes incisions by hand. The disadvantage of the method is the healing period of several days. About 10 to 30% of patients after surgery still need glasses (only weaker glasses) to see really sharply. Often, several years after the procedure, the patient has to wear glasses again, this time for near vision, because the incised cornea flattens over time, leading to farsightedness too much. Some patients also complain about the deterioration of visual acuity with the passage of the day. RK is the cheapest procedure to correct a vision defect, but the most risky, therefore in Poland, as in the world, this method is abandoned.

LASER PROCEDURES

Currently, the most commonly used refractive surgery procedures are procedures using the excimer laser – PRK and LASIK. The treatment with an excimer laser (excited dimer) consists in changing the curvature of the cornea. This laser produces a cold, pulsed ultraviolet beam with a wavelength of 193 nono meters, and with each pulse, the laser breaks the molecular junctions of the corneal cells with an accuracy of 0.25 microns. Often, only the removal of 50 microns of corneal tissue (about the thickness of a hair) is sufficient to obtain the correct amount of vision correction. An additional advantage of the excimer laser is the emission of cold light, which does not burn the corneal tissue.

LASIK (laser assisted in situ keratomileusis) is a technique whose aim is to model the surface of the cornea so that it can properly focus the image on the retina. LASIK is a two-phase procedure. In the first stage, a thin, superficial corneal flap is cut off. This can be done mechanically (using a special instrument: microkeratome) or laser (using a femtosecond laser). The corneal flap, like the lid of the canned food, is turned outwards. Then the excimer laser beam precisely models the exposed surface of the cornea. At the end of the procedure, the superficial corneal flap is put back in place.

The LASIK method allowed for the extension of the power range of the corrected defects. In the postoperative period, the patient feels no pain, only mild discomfort that lasts for several hours. He is not forced to wear a bandage, which allows both eyes to be operated on at the same time. Rehabilitation is the fastest in this method. The recovery period usually lasts several days, unlike PRK, where this period may last several weeks. This procedure allows for the correction of hyperopia up to +6.0 diopters.

PRK (photo – refractive keratectomy) is also a two-stage process. In the first stage, the corneal epithelium is removed mechanically, and then the deeper layers in the central part of the cornea are modeled with a laser beam. The scope of the procedure is set in such a way that the light is focused precisely on the surface of the retina. Removal of a thin layer of corneal tissue allows it to flatten or emphasize it and change the focusing force of the entire optical system of the eye.

After the procedure, the eye must be protected with a dressing and the patient may feel a little pain. However, in 10-20% of patients the pain may persist for several weeks. A significant improvement in visual acuity occurs immediately after the procedure, but complete stabilization is achieved after a few weeks. The effects of the treatment can be fully assessed after about half a year, because this is how long the corneal epithelium needs to regenerate completely and the cornea obtains its final shape. Quite often, mainly in patients with a large defect, there is a risk that during healing the cornea will take a different shape from the intended one, which may lead to, for example, astigmatism that is difficult to correct over time.
Using the PRK method, we can correct a slight degree of hyperopia. The effectiveness of this method reaches 95% -98%, but in the case of larger defects it significantly decreases. The PRK method cannot operate on both eyes at the same time and a three-month break is necessary.

The disadvantage of all the methods described above is their irreversibility. If something goes wrong, it’s hard to fix. All laser procedures (PRK, LASIK) are performed on an outpatient basis under local anesthesia. However, they are subject to strict surgical procedures.

Contraindications to laser vision correction are:

• age under 21
• no defect stabilization
• additional eye diseases (glaucoma, cataracts, retinal detachment, eye inflammation, keratoconus and corneal changes, dry eye syndrome)
• diabetes
• connective tissue diseases (so-called collagenoses) – e.g. rheumatoid arthritis, scleroderma, lupus, polyarteritis nodosa, psoriasis, Sjogren’s syndrome
• autoimmune diseases
• diseases with the weakening of the body’s immunity
• atopy and severe allergies
• active infectious diseases
• the individual’s tendency to form overgrown scars, called keloids
• implanted pacemaker
• pregnancy and breastfeeding.

Before laser vision correction surgery, you must not:

• I wear soft contact lenses for 3 weeks and hard contact lenses for 4 weeks
• consume alcoholic beverages at least 48 hours before the correction
• use cosmetics 24 hours before surgery
• If you are using oral contraceptives, please do not stop taking them in
  the period of 3 months before and after the procedure.

LENS TREATMENTS

Refractive RLE lens replacement

This method is an intraocular method involving the removal of the patient’s own, often healthy, lens and implantation of an artificial lens in its place. The procedure is performed under local anesthesia and, similarly to cataract surgery, the patient’s lens is replaced with an implant. Until recently, the disadvantage of this method was that the artificial lens does not have the ability to accommodate (adapting to acute vision both near and far). This method is therefore mainly recommended for patients with myopia after the age of 50 and for those who have corneal problems. In recent years, the market of intraocular implants has been developing more and more dynamically and multifocal lenses and accommodating lenses are already being produced. These treatments are associated with an increased risk of retinal detachment.

Phakic lenses

In this method, an artificial lens is also placed inside the eye. In the case of a phakic lens, however, the own lens is not removed, but the eye implant is attached to the eye with a translucent natural lens. Phakic lenses are often compared to contact lenses, which, instead of being placed on the surface of the eye, are permanently implanted inside the eye. The material of the phakic lens is similar to that used in lenses used in cataract surgery. Phakic lenses are designed to correct myopia from -5.0 to -23.5 diopters. During the procedure, it is possible to correct astigmatism at the same time. Artisan / Artiflex lenses used in our center are implanted into the anterior chamber and fixed on the iris. Cache’t lenses placed in the anterior chamber of the eye are also available. The advantage of this method is that it is reversible,

Latent hyperopia

In people over 40, the amplitude of accommodation drops to 2.5-3 diopters and it can only be compensated for far-sightedness with such a number of diopters, but then there is no additional optical power to see sharply “near”. However, in children, the flexibility of the lenses is so great that it translates into an amplitude of accommodation above 14 diopters [2]. It can compensate for hyperopia of the order of 11 diopters and 3 additional diopters, so that you can see sharply “near”, so in the whole range.

Farsightedness

With aging, the refractive index of the cornea and vitreous body typically decreases by 1.5 diopters at age 70 and by 2.5 diopters by age 80. However, myopia just benefits, and may even come to a natural compensation for myopia (with defects – minus 1.5 and minus 2.5 diopters, respectively). Presbyopia should not be confused with presbyopia.

DEFINITION

Presbyopia  (in Latin, presbyopia) is a disorder of accommodation in the aging eye. The eye becomes unable to focus properly, to sharpen images at different distances on the retina. Close-range vision deteriorates in presbyopia. It is a natural, physiological process resulting from the aging of the body.

Accommodation, or readjustment, is the phenomenon of the eye adapting to viewing objects at different distances. This process in the human eye takes place by changing the shape of the eye lens. The flexible lens changes its shape due to the intraocular ciliary muscles. Focusing your eyes on a distant object causes the ciliary muscle to relax and the lens to flatten. Focusing your eyes on an object close by causes the ciliary muscle to contract and the lens to round. Changing the curvature of the lens changes its focal length and thus changes its focusing ability.

With age, the hardening lens becomes harder, thicker and less flexible, losing its ability to bulge and flatten. This process usually begins after the age of 40 and is progressive. In the age of 60, the eye completely loses its ability to accommodate and it is not possible to properly see objects located close to the eyes. This problem affects eyes with short-sightedness, farsightedness and normoresight, that is, those that have never needed glasses before to see clearly.

 How Can I Deal With Presbyopia?

• Glasses

The easiest way is to use glasses for reading, writing and other precision activities performed at close range. Each eye after the age of 40 will require additional optical power to see sharp objects up close (e.g. when reading). Depending on the degree of loss of accommodation, the additional optical power will be in the range of +0.5 to +3.5 diopters greater than the power of the glasses “to the distance”. The power of near vision glasses also depends on what activities the glasses will be used for, and especially on the distance of the object on which the eyes are focused. Different glasses will require computer work (distance 50-75 cm), other precise DIY (20 cm), and still other standard writing and reading (35 cm). The closer the object is to the eyes, the stronger “plus powers” are needed.

Eyes also behave differently without and with an additional eye defect. In a regular eye with no additional distant vision defect, a sharp image of objects is formed on the retina at infinity, without any additional straining of the eye muscles. Such a patient will only need “plus” glasses for close-up vision, which he will have to take off to clearly see distant objects. In presbyopia, “near” vision correction always disturbs “far” vision, and in the normo-sighted eye with reading glasses, the patient will be bad he could see at a distance.

In the eye with blurred vision of objects in the distance (both in the case of hyperopia, myopia and astigmatism), you should first choose the right glasses to correct long vision, and then choose additional glasses with the appropriate power for near vision. The strength of the lens will depend on the degree of accommodation lost and the distance from the eyes of the usual work. Patients with distant vision impairment will therefore have to use two pairs of glasses: one for reading and the other for sharp vision of distant objects. It is possible to do it in one glasses, the so-called bifocals, in which the top of the glass is adapted to look into the distance and the bottom to the near. Unfortunately, the problem will be sharp vision of objects located at intermediate distances. You can deal with it by using progressive lenses with a variable focal length. They are more comfortable, but unfortunately more expensive.

In the case of small vision defects up to 3 diopters, the need for correction for farsighted and nearsighted people will differ. In small, undiagnosed hyperopia, with still efficient accommodation, the farsighted sight is able to see objects in the distance sharply, however, this is at the expense of the constant and harmful tension of the eye muscles. With prolonged tension and activities requiring constant eyesight concentration, it will cause many troublesome eye ailments.

Presbyopia is often confused with hyperopia, because in both cases the use of “plus” glasses is required to correct the defect. The coexisting presbyopia limiting or preventing accommodation, will cause that with longer visual work the farsighted viewer will not see sharply to the distance. In this sense, presbyopia exacerbates the symptoms of hyperopia.

In myopia, the symptoms of presbyopia are noticeable relatively late, as myopia intuitively begins to take off glasses to see clearly at close range. Removing the glasses is tantamount to adding a “plus” (ie with the opposite sign) optical power, equal to that of the glasses used. For example, myopia, with complete presbyopia, using glasses with a strength of -3 diopters, which perfectly correct far vision, will not need glasses at all for close-up vision. Nearsighted people with a visual impairment of -2 diopters will need near vision glasses with a power of +1 diopter, which is sometimes misinterpreted as a change from myopia to hyperopia.

• Contact lenses

 Contact lenses are an alternative to glasses. There are lenses with a special design, the so-called bifocal lenses whose principle of operation resembles bifocal glasses. Monovision, popular in the United States, is also possible, i.e. wearing a lens correcting distance vision on one eye, and wearing a lens correcting near vision on the other eye. However, not all patients can tolerate monovision well.

• Intraocular implants

As cataracts often appear in the aging eye in addition to problems with accommodation, it is possible to operate cataracts and presbyopia at the same time during the operation. This involves replacing a standard implant with a multifocal or accommodative lens.

• Laser operations

In recent years, the boom in laser vision correction has allowed the development of methods of correcting presbyopia as well. There are high hopes for the recently introduced femtosecond laser. There are also attempts to insert special implants between the corneal layers, allowing reading without glasses.