Presbyopia
As presbyopia (from ancient Greek πρέσβυς présbys "old" and ὤψ Ops "eye"), and presbyopia , or presbyopia called, refers to the progressive, age-related loss of Nahanpassungsfähigkeit of the eye by means of accommodation . It is therefore no longer possible to see clearly in the vicinity without suitable correction. Presbyopia is not an illness , but a normal age-related loss of function.
| Classification according to ICD-10 | |
|---|---|
| H52.4 | Presbyopia |
| ICD-10 online (WHO version 2019) | |
root cause
Due to sclerotherapy and loss of elasticity of the lens nucleus, the range of accommodation (also: accommodation amplitude ) steadily decreases. The maximum near point at which objects can just be recognized sharply moves further and further into the distance. Although this process begins in adolescence, it is usually not noticed at this point.
Change of the near point and the range of accommodation
For example, if a 10-year-old has an accommodation width of around 15 dioptres (dpt), this has already decreased to around 10 dpt for a 20-year-old and to around 7 dpt for a 30-year-old. At 40 years of age, the average width of accommodation is 4.5 D, so the near point of a person with normal vision moves to about 22 cm from the eye. This is where the first subjective complaints usually begin, which are expressed in the fact that you have to keep newspapers and books further and further away from your eyes in order to see something sharp. The fluctuation range in childhood is approximately ± 2.0 D, with this value decreasing to approximately ± 1 D with increasing age.
Average range of accommodation and near point depending on age:
| Age (years) | Accommodation width (dpt) | Near point (cm) |
|---|---|---|
| 10 | 13.5 | 7.5 |
| 20th | 10.0 | 10.0 |
| 30th | 7.5 | 13.5 |
| 40 | 4.5 | 22.0 |
| 45 | 3.5 | 28.5 |
| 50 | 2.5 | 40.0 |
| 55 | 1.5 | 66.5 |
| 60 | 1.0 | 100.0 |
| 65 | 0.5 | 200.0 |
| 70 | 0.25 | 400.0 |
Opportunities for correction
Since the normal reading distance is around 40 cm, the first optical aids, usually glasses , are necessary around the age of 45, which precisely compensate for the weaker close-up ability to the individual extent. Presbyopia does not affect a previously existing refractive error ( e.g. nearsightedness or farsightedness ), but always requires an additional correction for nearness (near addition ). In general, the weakest correction that allows comfortable near vision is chosen. In this way, the remaining accommodation capacity of the lens is used and the distant point is kept at the greatest possible distance from the eye. Corresponding to the progression of presbyopia up to around the age of 70, the glass thickness must be increased more and more for proximity.
The following can be used as guideline values for a near addition depending on age:
| Age (years) | Near addition (dpt) |
|---|---|
| 40-45 | 0.75 to 1.0 |
| from 50 | 1.5 to 2.0 |
| from 55 | 2.25 |
| from 60 | 2.25 to 3.0 |
The strength of a close-up correction, which can vary greatly from person to person, is always based on the respective distance at which activities are to be carried out. The following numbers are only average guidelines. They apply to people with fully developed presbyopia.
- For reading the newspaper (≈ 50 cm) while sitting, an addition of +2.0 dpt is generally sufficient.
- When reading lying down (≈ 30–40 cm), the document is usually held closer to the eyes (near addition: +2.5 D to +3.0 D).
- For manual work (≈ 45–60 cm) e.g. B. for carpenters, tilers etc. a rather weak near addition (+1.5 D to +2.25 D) is recommended.
- During screen activities (≈ 60–80 cm), the distance to the monitor is usually relatively large (near addition: +1.0 dpt to +1.5 dpt).
- For people with impaired visual acuity , excessive near addition of +3.5 D to +5.0 D, which takes on the function of a magnifying visual aid, can be useful.
Corrections to glasses
- Reading glasses with single vision lenses offer a large field of vision at close range. They are suitable for people who mainly work in close proximity and who can do without a clear distance view during these activities.
- So-called half glasses can be advantageous insofar as you can look over the upper edge of the glasses for distance vision. This type of glasses is suitable for people who do not need to use distance correction, but who also need good visual acuity close up.
- A bifocals has a large distance portion and the lower glass area a near portion without a transition zone with separating edge. The size and position of the near part can be varied individually. When the line of sight of the eye moves over the dividing line into the near part, an image jump takes some getting used to. In addition, when looking at the floor (for example when climbing stairs) a lowering of the head is necessary, otherwise the view falls through the near part and is thus seen blurred.
- Trifocal glasses are used when an intermediate zone is required for focusing at medium viewing distance. The intermediate segment usually has an addition of 50% of the near addition compared to the distance correction.
- Varifocal glasses have lenses in which there is a gradual increase in refractive power from the center of the pupil to the required reading area (variable) without a dividing line.
Glass thickness calculation
The lens equation can be used to estimate the required spectacle power, provided that the range of accommodation is known. It results from the reciprocal value of the distance (in meters) at which you can still see clearly from a distance with the correct distance glasses on.
With
- A rest : = rest accommodation or the reciprocal of the object distance 1 / g;
- R glasses : = strength of close-up glasses
surrendered
- A rest + R glasses = 1 / f min - 1 / b
or
- (3) R glasses = 1 / f min - 1 / b - A rest
Example : calculation of close-up glasses
Thumb formula
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Other correction options
In addition to glasses, there are various other methods of cosmetically inconspicuous compensation for presbyopia, all of which are based on pseudo-accommodation methods:
- Monovision : One eye is attuned to nearness through a contact lens
- Multifocal contact lenses
- Multifocal intraocular lenses
Since 2000, artificial lenses have also been implanted which, through minimal axial movement in the capsular bag, bring about optic shift accommodation (analogous to the Schachar theory). However, the results have a wide range due to too many unknown influencing factors. With such “accommodative” intraocular lenses, vision is no worse than with classic artificial lenses, but a reliable prognosis regarding the reading ability to be achieved cannot yet be made.
In the USA, a corneal implant was developed ( KAMRA implant ), which is supposed to represent a correction for presbyopic people based on the principle of the Stenopean gap . Two other monocular corneal implants for presbyopia correction are currently approved in Europe and are offered by individual eye clinics in Germany. As a tiny implanted hydrogel "cushion", the Raindrop inlay causes a slight protrusion and thus a local increase in the refractive power of the cornea with the effect of a multifocal corneal surface. Bifocal lenses implanted intracorneally achieve a similar effect with a ring of positive refractive power around the flat center (Presbia FlexiVue Microlens).
Presbyopia and refractive errors
Presbyopia does not affect the objective extent of axial refractive errors such as myopia and farsightedness . Therefore, no real functional compensation of such ametropies is to be expected from them. Nevertheless, a decrease in the ability to accommodate can affect vision in the case of an axial refractive error.
Presbyopia and farsightedness
Presbyopia is in the German language often called presbyopia called. However, this term should not with the equally as farsightedness called hyperopia be confused. The latter is a specific form of axial refractive error that has nothing to do with presbyopia.
If there is uncorrected or undercorrected hyperopia , which up to now has been fully or partially compensated for by means of accommodation, the presbyopia-related loss of accommodation also increases the need for a corresponding remote correction in the form of glasses or contact lenses.
Presbyopia and myopia
Short-sightedness ( myopia ) changes the area of accommodation to the extent that the near and far points are closer to the eye. Myopia can sometimes mean that nearby presbyopes can see properly, or at least better, simply by removing their distance correction . In the optimal case, this situation is given when the purely numerical extent of myopia, irrespective of the mathematical sign, corresponds approximately to the value of an objectively required close-up correction. The coincidence of such optical conditions is purely coincidental and in no way means that there would be any mutual change or active influence with regard to myopia on the one hand and presbyopia on the other. However, it is not uncommon for a person with a myopia of −3.0 D and fully developed presbyopia, for example, to not need any correction to read at a distance of 35–45 centimeters.
Web links
literature
- Axenfeld / Pau: textbook and atlas of ophthalmology . With the collaboration of R. Sachsenweger u. a. Gustav Fischer Verlag, Stuttgart 1980, ISBN 3-437-00255-4
- Karl Mütze: The Accommodation of the Human Eye . Akademie-Verlag, Berlin 1956 (with extensive bibliography)
- Duane: Studies in monocular and binocular accommodation with their clinical applications . In: Am J Ophtalmol , 1922, 5, pp. 865-877.
Individual evidence
- ^ Wilhelm Gemoll : Greek-German school and hand dictionary. Munich / Vienna 1965.
- ↑ Augustin: Ophthalmology . 3. Edition. Springer, 2007, p. 591
- Jump up ↑ JJ Whitman, P. Dougherty, GD Parkhurst, J. Olkowski, SG Slade, J. Hovanesian, R. Chu, J. Dishler, DB Tran, R. Lehmann, H. Carter, RF Steinert, DD Koch: Treatment of Presbyopia in Emmetropes Using a Shape-Changing Corneal Inlay: One-Year Clinical Outcomes. In: Ophthalmology . tape 123 , no. 3 , 2016, p. 466-475 , PMID 26804761 (English).
- ↑ SMC Beer, R. Santos, EM Nakano, F. Hirai, EJ Nitschke, C. Francesconi, M. Campos: One-Year Clinical Outcomes of a Corneal Inlay for Presbyopia . In: Cornea . tape 36 , no. 7 , 2017, p. 816-820 , PMID 28445192 (English).