Typically, presbyopia is presented by difficulties in reading at near distances – the affected person helps himself by putting the text at a greater distance, by tilting his head back or reading in brighter light. When looking from near objects into the distance the vision gets foggy, even headache and eyestrain can occur. The mentioned symptoms are more distinct in people who need to concentrate for long periods on near objects – e.g. a computer screen.
Presbyopia (the term comes from Latin “presbys opia,” which means “an old eye“) is an eye defect connected with aging and affects in fact all people over the age of 45. The defect is caused by natural aging of the intraocular lens, which (due to protein sedimentation) gradually loses its elasticity and plasticity, and enlarges and compacts. It loses its ability to focus on near objects. The occurrence of presbyopia is mainly dependant on age, but also on the refractive condition of the eye.
A routine examination of visual acuity is done by a device called an autorefractometer. The doctor will seat you in front of it and let your chin and forehead lean against a comfortably formed rest. The doctor himself will be seated in front of you. In front of one eye, you will see a defocused fixation point – typically used images are a picture of a house in front of a landscape, a balloon in the sky or a boat sailing in the sea. The point gradually sharpens and blurs again. The device measures the amount of optical power necessary for dioptre corrections. Examining both eyes takes about 5 seconds and is completely painless.
A more precise examination of the near visual acuity is done by Jaeger chart. They contain text written in letters of different size. Every line is labelled with a number that equals the distance from which you should be able to read the letters without difficulties. To examine near visual acuity you will be asked to cover one eye with your hand – only slightly, without pressure, otherwise you can decrease its ability to distinguish. Afterwards you will be asked to read the chart in lines, or only the letters indicated. The same will be done with the other eye.
To measure eye defects the doctor will use special glasses and a set of corrective lenses. Wearing glasses you will read again from the charts and the doctor will add or remove lenses until your near vision is clear, acute, and sharp. There is no a special preparation needed for this examination. We only recommend not going partying or staying up late– tiredness can distort the visual acuity and the results of the examination.
Dioptre glasses serve as a visual aid to correct vision. They usually consist of a fixed frame into which optical lenses are attached. The frame should not narrow the visual field and its shape should be adapted to the face. The optical lens is an optical set of two centered areas, in most cases spherical. The lenses of the glasses were initially made of glass, nowadays they are made also from different plastic materials to reduce the risk of breaking and because of their lighter weight compared to glass lenses. The disadvantage is the softness of the material – plastic lenses are exposed to scratches. Nevertheless, the majority of plastic lenses can undergo the so-called “hardening” treatment, and can thus provide greater resistance to mechanical damage. Coating of the hydrophobic layer protects the lens against the concentration of the moisture and due to a very smooth surface provides easier cleaning. Lipo-phobia coating means higher resistance against grease, e.g. fingerprints. Anti-glare coating might be also applied on lenses, which prevents creation of glares, reflections on the surface of the glasses. Advantage is also smaller eye tiredness in artificial lighting, while working on a computer or watching TV, as well as better vision while driving (particularly at night) etc.
Presbyopia can be comfortably corrected with glasses with multifocal lenses that have different focal points. Multifocal lenses are usually cut into the shape of five concentric circles with different dioptre values. It means the user can see comfortably at near and middle (working) distances and even at a far distance. Glasses with bifocal lenses represent another solution. Bifocal lenses have a dioptric value which corrects distance vision in its larger upper part, while in the remaining lower part have a dioptre value correcting near vision. Unfortunately, bifocal lenses do not allow sharp vision at middle distances and thus while changing view from distance to near the image “jumps.” The last and the least comfortable option is to change glasses for near and far.
Contact lenses are a modern optical device intended to be used directly on the cornea. Its curvature replaces the curvature of the anterior corneal surface. It serves mainly to correct short-sightedness, long-sightedness, astigmatism, or presbyopia. They also have a therapeutic or protective function in certain eye diseases, for instance, and are used to moisture the cornea when damaged. They can also be used as bandages after eye surgery or as a drug carrier etc.
The technology and production of contact lenses was developed by the Czech scientist Otto Wichterle. Since then contact lenses have experienced significant changes due to modern technologies. According to the material used, they can be divided into two main groups – hard and soft lenses. On one hand, due to their non-porosity, hard contact lenses do not adsorb chemicals and other evaporations. They also have the ability to replace the natural shape of the cornea by a new reflecting surface. On the other hand, they are not oxygen permeable and prevent the eye from “breathing.” When applied for the first time, they are usually uncomfortable and it takes some time to get used to them. Correct usage must be checked regularly. They are mostly recommended for long-term wearing, such as yearly. On the contrary, soft contact lenses are highly permeable to oxygen. When applied for the first time, they are immediately comfortable due to their soft material. However, they are made of less durable material, which wears out quickly. It is necessary to change them regularly as sediments from tear film are formed. They are mainly designed for short-term wearing, such as daily, monthly, etc.
Presbyopia can be corrected with multifocal or bifocal contact lenses, which correct simultaneously both near and distance vision. Their function is similar to multifocal or bifocal glasses. Dioptre values change fluently from the middle of the lens to its edges – they can be increased or reduced. In most cases, the middle part is adjusted for distance vision while the flattened periphery is adjusted for near vision.
Refractive lensectomy and intraocular lens implantation
To treat dioptric defects a method known as refractive lensectomy can be used. Its objective is to correct vision in such a way so that patients no longer need to wear glasses after surgery or at least do not need such “thick” glasses. By means of ultrasound, the original clear lens is emulsified and its remains are aspirated from the eye. An artificial intraocular lens with a pre-calculated dioptric value is implanted into a preserved pouch. Compared to procedures carried out on the cornea only, this procedure requires more intervention.
Initially, artificial, hard (inflexible) intraocular lenses made of plastic (polymethylmethacrylate) were used. The development of delicate surgical methods led to the demand for soft, flexible intraocular lenses, made of biomaterials (silicone, acrylic, collamer etc.) A soft, folded lens is inserted into the eye through a small incision and, once inside the eye, the lens unfolds into the required shape. According to the visual correction needs, it is possible to select monofocal or multifocal lenses. The first provides clear vision of a single focal point in the lens that is either near or far. The latter allows sharp vision at multiple distances. The surgery is performed on an outpatient basis under local anesthesia and takes about 15-30 minutes.
Jaeger’s charts are used to examine near visual acuity, which means reading at a distance of approx. 40 cm. These charts have a coherent printed text, whose paragraphs are printed in letters of different size.
This device is designed for anterior eye segment surgery. It enables clouded lenses to be emulsified by the means of ultrasound. The remains of the lenses are then aspirated and replaced by a special solution. It guarantees the preservation of a stable volume of the eye during surgery. Our clinic uses phacoemulsifiers from the Alcon Company, which belong to the best and most advanced devices of its kind.
This device allows the surgeon better visibility of the operation site during microsurgical operations performed inside the eye.
This device uses a laser beam to determine the correct dioptre values of the intraocular lens (it is implanted instead of the original cloudy lens). As eye contact with the device is not needed, measurement accuracy is higher. Anesthesia of the eye is not required and the risk of transmitted infection is reduced. Our clinic uses a biometer from the Carl Zeiss Company.