Prevalence of presbyopia
Presbyopia is a condition caused by a change in the elasticity of the lens occurs with age. This reduction of the elasticity of the crystalline lens results in a gradual reduction of the power of accommodation: near vision becomes more and more blurred. The age of entry in presbyopia is relatively constant: between 43 and 46 years, but there are some variations in ethnic origin.
Age and presbyopia
The world's population ages, which mechanically causes the growing increase in the number of presbyopes, some do not have access to a suitable means of optical correction.
The lens allows the update in near vision by deforming in a passive way; with age, the amplitude of this deformation is reduced. The accommodation is quantified as the inverse of the distance (in meters) of clear vision: his unit is therefore (as for the vergence) the diopter. At the age of 12, a child can accommodate to see net an object placed 8 cm from the eye: its amplitude of accommodation is equal to 1/0.08 or 12 diopters. This amplitude continues to shrink with time and 45 years, residual accommodation is more than 3 diopters which does more to see net targets located less than 1/3 = 33 cm. At the age of 60, the amplitude of accommodation is zero, and optical assistance is necessary to see up close.
At what age does presbyopia start?
The first symptoms of presbyopia are usually felt after 40 years, in special situations where the reduction of the amplitude of accommodation is a gene for near vision source: very small print and insufficient lighting. Presbyopia is the result of a phenomenon whose evolution is progressive and continuous (progressive loss of accommodation); several elements can be regarded as marking the beginning of presbyopia: the new sensation of a Visual gene closely and the need to 'force' in an active way to see enough net are classic symptoms. Instinctively, the presbyter tends to increase the distance eye work to relieve the need for accommodation.
When correct presbyopia.
The age at which the use of corrective lenses for vision closely becomes necessary is variable, because it is based on the following factors:
-the degree of residual capacity of accommodation
-existence of a correction in distant vision: uncorrected slight myopia promotes near vision
-the climate and the living place: presbyopia seems to occur earlier towards the equator to the poles
-the degree of Visual requirement: presbyopia will be felt even more early reading habits include the need to read fine print texts, where tasks much soliciting near vision
-sex: women could be achieved a little earlier than men
-ethnicity: Africans have an age of more early presbyopia (40 years) than the caucaseiens (45 years)
To estimate the prevalence of presbyopia, agree on the definition for it; which can be subjective (need to wear specific correction for vision closely that it is that distance vision) or objective (need of correction for reading when far vision is corrected at best). The existence of a slight myopia may allow an objectively far-sighted individual to dispense with reading glasses: the best definition of presbyopia is so priori objective.
Prevalence compared to presbyopia
In countries developed countries populated by a predominantly white population (Europe, Australia, North America), it is estimated the prevalence of of presbyopia at 83% and an age of installation of 45 years. In other regions such as the India, South America, Africa the prevalence of presbyopia is estimated at 58% for an installation of 40 years age.
By combining these data with some projections, it is possible to predict an overall prevalence of presbyopia at 1.4 billion people by 2020, against a little more than a billion in 2005. It is estimated that two thirds of presbyopes live in countries less or underdeveloped, and that among these more than half did not have a correction for presbyopia. Ultimately, our planet has more than a billion of presbyopes. Of those, slightly more than half of is not access to care and a suitable correction.
These figures underline the importance of the 'market of presbyopia' for the actors of the sector: ophthalmologists, optometrists, manufacturers of Mount, especially contact lenses and glasses. A walk in the commercial and urban center often allows to discover a large (and growing) number of optical stores. -l' increase in the prevalence of nearsightedness also contributes to this development. A significant part of the advertising (radio, T V, press) is occupied by the manufacturers of ophthalmic lenses. Optics is the main item of the mutual health insurance scheme. Finally, the surgical correction of presbyopia is a growing interest, which attests the many techniques and strategies currently: implants, multifocal, technical correction multifocal laser, intra corneal implants, etc. The large research budgets are devoted to the study of innovative fixed devices as accommodatifs implants, surgery of the lens (restitution of part of its elasticity by incisions made in the) femtosecond laseretc.).
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