What presbyopia is?
The presbyopia is natural state of the eye after 40. year of age. As all the human tissues get older, so does the crystalline lens. In children or young adults the lens is flexible, it is able to change it´s shape easily according to the need of focusing. In older people it becomes more rigid and it´s ability to change it´s shape slowely disappears.
People without refractive error or people with far-sightedness need their crystalline lens to increase it´s power to focus the objects in the near. The lens increases it´s power by changing it´s shape (it becomes more round – accomodates). In the time when the lens is not able to change it´s shape sufficiently the problems with near vision begin.
People with short-sightedness (myopia) use their crystalline lenses differently. Their lenses even in their relaxed state have so big dioptric power, that are naturally focusing near objects (but they have problems with objects in distance). If people are myopic only slightly they may need to accomodate to see very near objects – but their need of accomodation is lower than in people without refractive error or in hyperopic people.
What are the symptoms of presbyopia?
Presbyopic people typically have to place their cellphones, tablets, books etc. further and further from their eyes to be able to read it. Finally happens that their hands are too short to be able to hold it in the “readable” position. Headaches can appear during reading. People may tear, the eyes can burn, can be “tired”. The problems typically start in poor light conditions – sometimes people even have to switch on the light to read some small letters.
How to solve presbyopia?
We can solve it conservatively or by surgery.
The most common solution is wearing of glasses for the short distance. If it is needed we can combine the diopters for far distance and short distance in one glasses. There exist more variants of this combination – bifocal glasses, trifocal glasses, eventually progressive glasses. The last become more and more popular nowadays.
Bifocals are focused on one distance in the upper segment and on the second distance in the lower segment.
Trifocals have segment for far distance, middle distance and short distance. There is possible to place the segments differently – e.g. middle distance in the upper segment, far distance in the middle segment and short distance in the lower segment. It can be convenient for people, who in their work need to see some panel above them and at the same time write something.
Progressive lenses (glasses) are made in the way that in the upper part are diopters for the far distance, in the lower part the diopters for short distance and inbetween is continuous transition. On the sides of the lenses is unfortunatelly the zone of distorsion caused by technical reasons. The tolerance of progressive lenses depends in particular on good individual choice of the type of the lenses – respectively choice of suitable “corridor”.
There is also possibility of bifocal or multifocal contact lenses. Not everybody likes them, but there exist people who adore them a lot.
In classical monofocal contact lenses is also possible to establish so called “monovision” – one eye is corrected to see far objects and the second eye to see objects which are closer. The 3D vision can be affected a bit, but it works quite well.
Surgical correction of presbyopia
There is plenty of surgical options to correct presbyopia. Corneal surgeries, adding the artificial lens to your original lens, exchange of your otherwise healthy (or already clouded) lens by artificial lens – multifocal, eventually monofocal in monovision setting.
I´m probably too conservative, but i don´t like the corneal presbyopic surgery. The cornea is for the eye crucial, it´s tissue heals poorly and it´s exchange in the worst case is very complicated. The corneal presbyopic surgery usually consists from implantation of some inlay or stenopeic ring (some pinhole) into the cornea. The positive thing on corneal surgery is that there are not complications resulting from opening the globe itself. We work only in it´s wall.
Multifocal artificial lens added to your original “human” one is only temporary solution – before your own lens gets cataract and it´s exchange is necessary. It can take a few decades but also only a few years. And the time we are not able to predict.
Exchange of your own (even healthy) “human” lens with the artificial multifocal lens. This is definitive solution of presbyopia. The lens will stay in the eye forever. But every surgery has it´s risks – including deteritoriation of the vision. Multifocal lenses can reduce contrast sensitivity, there can be halos around the lights, or some glare. The material of the artificial lens can eventually get cloudy in rare cases – and the exchange of that lens is usually more difficult than the first surgery (variation of cataract surgery).
Your own lens exchange with monofocal artificial lens in the monovision setting. There is, like in contact lenses, some probability of reduction of 3D vision. But in comparison with multifocal lenses there is lesser risk of optical phenomenons which usually don´t appear in monofocal design of lenses. Monofocal lenses are used already decades – so there is a lot of experience with them.
