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Presbyopia


The term presbyopia directly translates to “old sight”, which is not necessarily a flattering term, however, it does give some indication of the period of life in which it occurs.


Presbyopia is a normal aging change that everyone experiences at some point in life. Interestingly enough, the onset varies depending on the area of the world you live in. The closer to the equator you live, the earlier the onset. Presbyopia typically is noted at age 37 in India and up to 46 in Norway (1). This study ultimately concludes that the difference has to do with average ambient temperature. It could be argued also that the ultra-violet light (UV) exposure increases near the equator. UV light can be damaging to many body tissues, if one is exposed long term.


A clear crystalline lens sits behind the iris of the eye. This lens is connected to rope-like structures called zonules that connect 360 degrees around the lens. The other end of the zonules are connected to a special muscle called the ciliary body. When an object is viewed at near, the object is blurry until the ciliary muscle flexes; as it flexes, it pulls on the zonules and subsequently changes the shape of the crystalline lens. By changing the shape of the lens, the refractive power (focusing power) is changed and thus brings the near point object into focus.


Usually around 40 years of age, this lens begins to lose its ability to change shape, even when the zonules pull and thus can no longer bring near objects into focus. It is most often thought that the lens hardens, becomes thicker and less elastic and thus unable to change shape.


The easiest and most common way to address near point blur brought on by presbyopia, is by using bi-focal glasses or a separate pair of reading glasses. These specific glasses perform the “focusing” for you. They work well, however, they are usually set at a fixed focal point and sometimes can make it difficult to see near targets at varying distances.


Presbyopia is a normal age change that is most commonly identified as near point blur beginning around age 40.


 
  1. Miranda MH. The environmental factor is the onset of presbyopia. In: Stark L, Obrecht G, eds. Presbyopia, New York. professional Press; 1987: 19-28.

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