The Cause of Presbyopia
Presbyopia is sometimes mistaken for myopia (farsightedness), but there are inherent differences between the two conditions:
- Presbyopia: An age-related problem caused by the stiffening of the lens which results in its reduced flexibility.
- Myopia: A refractive error that originates from a misshapen cornea that usually manifests during childhood.
Hardening of the crystalline lens
The crystalline lens located behind the iris in the eye is a biconvex transparent layer made up of cells that have no blood supply. The lens is soft and flexible and controlled by ciliary muscles that push and pull it into shape in order to focus on objects at various distances.
As you age, the lens hardens and loses its natural flexibility resulting in an inability to adjust correctly to bring near objects into focus.
Refraction in the eye
The cornea and the crystalline lens are responsible for refraction or the bending of light in the eye with the cornea accounting for two thirds of the eye’s refractive capability and the lens making up the other one third.
Refractive power is measured in diopters (D) and each eye has a total of 60D. Any inability to focus objects up close is reflected in a positive (+) prescription.
The decline in the lens’s elasticity declines gradually, usually at a rate of 0.3D per year but between the ages of 40 to 64 this decline can become more rapid.
Alternatives to reading glasses
Corneal inlays combined with refined laser technology are the latest breakthrough in corrective refractive procedures used to treat presbyopia.
Presbia is one such innovative corneal inlay that alters the near power in the pupil centre without infringing on distance power.
How Presbia works to reverse presbyopia
The Presbia corneal inlay has a neutral center point that has zero refractive power, while the peripheral zone houses positive refractive power.
This unique design works by creating two focal points in a patient’s non-dominant eye so that far vision doesn’t change while near vision is corrected.