The first symptoms are deterioration of vision near. Objects under close examination spread out. A woman struggles with the manicure. A man goes fishing and there he realizes that he is pushing the worm with difficulty. And while the distant vision did not change. Traditionally, this condition is called "short-arm disease" – like and good vision, but the length of the hands is not enough for clarity near. This is for those over 40.
This is presbyopia. With age, the sight of a person in terms of ease of focusing at different distances deteriorates. The exact reasons for this "depreciation" of the visual apparatus are still being investigated: it is known, for example, that this mechanism works only in higher primates. In dogs and cats, presbyopia is not present, there are monkeys. By the way, in part, therefore, it is difficult to study presbyopia: a living object is needed to study dynamic refraction (accommodation).
The lens becomes denser and less elastic, the ligamentous apparatus suffers, the muscles lose the ability to act as before – presbyopia arises. Until recently, the theory of accommodation of the German physician Helmholtz, put forward in the 19th century, which affects only the lens and its ligamentous apparatus, was recognized as the only correct one, but more recent studies say that all the eye structures – the cornea, the vitreous body and even the retina are involved. The result of presbyopia is the loss of the ability to accommodate, that is, the ability to view objects at different distances without additional correction.
When Presbyopia Appears
The average age of first symptoms is 40 years, rarely later – I had patients who at 50 years felt quite Comfortable, but by 60-70 years began to suffer from presbyopia (in combination with cataracts). Presbyopia is considered to be as natural a physiological process as the appearance of wrinkles or graying with age.
In my practice, patients have very little idea what exactly is happening. Almost everyone complains that "I spoiled my vision with a computer". No, it's easier. You are older.
How does this affect those who have nearsightedness, farsightedness or astigmatism? In a person with absolute vision (no matter whether natural or after laser correction, or with implanted intraocular lens), subjects near begin to blur. The text in front of the nose is not visible either on 8 centimeters, or on 15 – and already somewhere far away. To read need glasses for near. Vision does not deteriorate in the distance. Points for the distance, if any, remain the same.
Myopic with a weak minus and without pronounced astigmatism can longer save the opportunity to read without glasses, although the glasses for the distance are not going to disappear. Moreover, they will interfere when working near, they will need to be removed. The ease of focusing in the old glasses or contact lenses will disappear. Years to 50-60 will be another pair of points with a small now a plus. In short, the plus to minus will not go to zero.
When myopia is stronger, a second pair of glasses, weaker, is needed to read and do small-scale work. As a result, by the same 50-60 years there will be 3 pairs of points – the strongest in the distance, weaker by 1-1.5 diopters for the average distance and weaker by 2-2.5 for reading and near. In general, there are not many "pluses" in the minus.
Far-sighted people feel presbyopia symptoms even earlier – after 35 years. This is because plus is added to accommodation plus for accommodation. In the end, after wearing a couple of years of reading glasses, they begin to notice that in these glasses suddenly it became and far into the distance is clearly visible, but for nearer ones an even stronger correction is required. And such patients run to the ophthalmologist with the story that the computer, or books, or work "spoiled" their eyes. And they do not always believe the story that changes of such a plan are irreversible and incurable by drops, miracle pills, strengthening super-exercises, sentences and urine of a young pig.
As a result, farsighted people after 40 years get reading glasses, somehow retaining their ability to see far into the distance. Somewhere after 50, after the unsuccessful struggle against presbyopia, still put on two or three pairs of glasses or progressive lenses, or turn for surgical help.
Worst of all astigmatam – the quality of the picture they have at all distances is poor . Therefore, the higher the degree of astigmatism, the greater the binding to points. In the end, all ends also with a few pairs of glasses.
If you ever had an eye examination with a pupil dilating (before the first prescription of glasses, before surgery, when examining the fundus, etc.) – the first hour after the drug treatment, you Just get a simplified presbyop simulator. Only the difference is that everything around will not seem so intolerably bright.
How does this affect vision correction and laser surgery in youth?
The first case: a patient aged 18 years (before this eye is still actively developing) to about 40 years. In this situation, the choice is the full correction. At the age of older, in the absence of other problems that may appear at this time (cataract, glaucoma, retinal dystrophy, etc.), we make an amendment to presbyopia.
In any case, after laser correction to emmetropia (a condition when the image gets to the retina) any optics becomes close to normal. This translates a person into a standard of his age, a presbyope, eliminates the need to wear glasses for distances and gives a comfortable feeling in everyday life. And presbyopia should be perceived as a given to the age.
If you want to reduce dependence on presbyopia – we find compromise surgical options. There are a lot of them, about this further in the text and in previous posts.
And if I already have presbyopia?
If the patient is already with presbyopia and several pairs of glasses completely Suits, then in this situation we say: if you are satisfied with glasses – this is not a disease. Walk, try. But many are not ready, and really want to make a correction. This is especially true of women – there is a stereotype that a woman who wears glasses for reading is already a grandmother (plus glasses are always made with large glasses or, even more old, put on "nose"). Athletes and people with an active lifestyle are also willing to go for correction.
Correction is made according to needs. We ask in great detail about the occupation of a person and his hobby. For example, if the patient is a jeweler or embroidered – a near focus is needed. The patient is done with the chosen focal length, he estimates how comfortable he is. As a result, the optimal method is chosen.
Since different focal distances are needed for different tasks (simplifying them, three: close focus – reading, embroidery, average distance – computer, music stand, easel, long-distance driving, theater and Etc.), you can apply several techniques. I will not write about methods that have been experimentally conducted for the last 20 years – incisions with a laser and a scalpel on the sclera, implantation of rings and accommodation lenses, etc., which showed its inconsistency. Here are the options:
1. Method of monovision. Two eyes are adjusted in different ways: one for near, the second for distance with a difference of about 1-1.5 diopters. The leading eye helps to see into the distance, the unknowing – near. Since not every brain can get accustomed to this, tests with glasses or lenses are required, until the patient is convinced that this method suits him. The essence is very simple – you need to learn to switch the slave and the leading eyes at different distances of the object. The brain does this automatically.
This method is available both for glasses and for contact lenses, phakic intraocular lenses, artificial lenses and laser correction.
This is the principle of monovision.
2. Incomplete correction in laser surgery. It's simple – a patient with a vision -6 diopters receives a correction to -1 diopter, and as a result can relatively comfortably drive a car and read. The type of laser correction does not matter, of course, under equal conditions I am for SMILE technology as the most progressive and safe. You can read about it in detail here.
The method is also available for all types of correction.
3. Laser correction with presbyopic profile (with multifocal cornea) – PresbyLASIK. On the cornea with a laser, you can cut out almost any complex figure with filigree precision, so you can make a lens that will have several focal lengths. The coarse approximation is that the Fresnel lens is applied to the eye (although, of course, modern profiles are much more complicated). Payback – much more beautiful aberrations. Each laser manufacturing company comes up with its own profiles and methods for creating them. Still, the market is huge – one hundred percent of patients are their consumers. Therefore, the best minds work on this.
It's bad that in such a situation an irregular cornea is done. That is, then it is more difficult to calculate the artificial lens, so long as we can not take into account these irregularities. And somewhere in 5-10 years, you will definitely need a repeated correction – presbyopia develops. The patient may feel chromatic distortion, coma. The rays on the retina are not focused to the point, but to the smeared block, or to the stellar spot.
This is how the multifocal cornea looks
4. There is another alternative: the introduction directly into the cornea of a special lens with a hole in the center. In fact, this is the setting of the diaphragm. That is, increasing the depth of the sharply displayed space by reducing the amount of light entering the retina – we leave only those rays that go through the center of the lens of the eye. In Russia, these lenses have not yet been certified. The world is pretty active. Reviews are different, in our German clinic they are not recommended. Of the obvious shortcomings – interfere with the side effects of optical, heavier in the twilight.
5. Implantation of multifocal phakic lenses. The technique is similar to the operation with refractive phakic IOLs. As a result, the cornea and its own lens are preserved. They do not interfere with the work of the eye until the cataract ripens. But they do not fit everyone for anatomical parameters – the distance between the iris and the lens. The lens grows, not everyone has enough space for the implant in the back chamber of the eye. It is necessary to take into account the width of pupils of the patient, otherwise they can also interfere with aberration due to multifocal optics.
As it happens, you can read in the post about the types of correction and the continuation of the eye and its biomechanics: here
The result – we can not make a presbyopic eye with the eye of a 20-year-old man. Any choice is a compromise between image quality, convenience and the ability to see near objects.
What exactly does not help?
1. No drops, tablets (even large and red), dark rituals and folk methods can not correct the presbyopia. But obscurantism wins, so people believe in it. And he asks for a pill so that everything goes by itself. Doctors in polyclinics sometimes meet, counting either on the effect of a placebo, or on a pharmacy award for a plan for selling drugs. And the Internet is "teeming" with offers, how to do "from -5 to 1", "read without glasses to old age" and "see through walls" without an operation. By the way, often for a lot of money.
2. Exercises of the muscles of the eyes can slightly improve eyesight (in general, "charging" for the eyes is better to do and being a healthy person), remove some of the effects of fatigue or muscle spasms (as a rule, at this age it is not). But nothing can be done with presbyopia systemically. Nevertheless, you can try to work an hour a day daily. It will not be worse. Often, in order not to wear eyeglasses for nearness, such tricks as the backlighting of the mobile phone menu in the restaurant, buying a phone with buttons larger, increasing the font on the electronic screen, etc. are used
How to measure accomodation and calculate Presbyopia?
To calculate the reserve of accommodative abilities for the patient, read the text located at a distance of 33 cm from the eyes. Each eye is examined in turn. After this, lenses are placed in front of him: the power of the maximum positive lenses with which the text can be read will be a negative part of the relative accommodation. The use of positive lenses causes a decrease in the tension of the ciliary muscle.
The power of the maximum negative lenses with which text is still possible is determined by the positive part of the relative accommodation. The use of negative lenses causes an additional stress of ciliary muscles, this part of accommodation is also called a reserve or positive Reserve relative accommodation. The sum of the positive and negative parts (without taking into account the sign of the lenses) shows the volume of relative accommodation.
As the body ages, the reserve capacity of accommodation gradually decreases. So, according to Donders, in patients with normal vision at 20 years, it is about 10 diopters, 50 drops to 2.5 diopters, and by 55 years – to 1.5 diopters. There are modern instruments that automatically measure static refraction and dynamic refraction (accommodation) in automatic mode. And we can observe this process in the course of UBM (ultrasonic biomicroscopy), where we observe the state of the lens and its ligaments.
For the correction of presbyopia, all the same optical glasses are used for near. To determine their strength, the formula is used: D = + 1 / R + (T-30) / 10
In it, D is the value of glass in diopters, 1 / R is the refraction for correcting the optics of the patient (nearsightedness or farsightedness), T is the age in years.
This is how the practical calculation of this indicator for a patient of fifty years old looks
If a person has normal vision, D = 0 + (50-30) / 10, that is +2 diopters.
With myopia (2 diopters) D = -2 + (50-30 ) / 10, that is, 0 diopters.
With farsightedness in 2 diopters D = + 2 + (50-30) / 10, that is 4 diopters.
And this is for sure Not CVS?
Symptoms in computer vision syndrome (CVS) may be It is the same as in early presbyopia. Naturally, it is necessary that you looked an ophthalmologist. However, if you are 40 – 99.9%, that it is not CVS.
There are several pathological, but temporary changes in accommodation, this includes the spasm of accommodation. Then we are talking about an abrupt increase in the refraction of the eye, which is due to the lack of relaxation of the fibers of the ciliary muscle. In doing so, we determine a sharp decrease in visual acuity (especially in the distance) and visual performance in general. By the way, such a state can easily be obtained by poisoning with organophosphorous agents and some drugs.
There is also the notion of the habitual excess supply voltage – PINA. It causes an increase in the initial refraction of the eye (more often in children), which can progress at different rates. This condition is provoked and maintained by an incorrect mode of visual activity, especially at close range.
Uncorrected asthenopic patients often have accommodative asthenopia, a condition in which rapid eye fatigue occurs during work.
The paralysis of accommodation is accompanied by the focusing of the eye at its farthest point. The distance depends on the initial refraction parameters. Paralysis can also occur against a background of general poisoning of the body (for example, with botulism) and with the use of certain medicines.
And under presbyopia is meant the age-related decrease in accommodative possibilities, characteristic for people older than 35-40 years.
What is further along with the development of presbyopia and closer to cataracts? Presbyopia progresses over time, at 60-70 years it reaches its maximum and eventually flows into a cataract. If there are opacities in the lens – the quality and amount of vision is markedly reduced. And the question naturally arises about the surgery of the lens, replacing it with a new one. I described this in previous posts about cataracts and artificial lenses.
Briefly, if the new lens is single-focus, then glasses for some distance will be needed, if multifocal – will get maximum independence from the glasses. Again, you can consider the version of the monovision.
The important thing is that you should not wait for cataract ripening and you should leave it when it starts to interfere. The choice of an artificial lens is strictly an individual task, which only surgeons with a lot of knowledge and experience of implantation of various IOL models can do.
The accommodation is still being studied, because it is unclear how it works. Например, около 5% пациентов и искусственным монофокальным хрусталиком могут получить так называемую «аккомодацию псевдофакичного глаза», то есть научатся менять фокусное расстояние хрусталика. Как это повторять – непонятно. Поэтому, вполне возможно, нас в будущем ждут серьёзные сдвиги по этой теме. Однако в перспективе 10 лет пока ничего серьёзного, увы нет – мы очень тщательно следим за всеми клиническими испытаниями.