Presbyopia is an age-related change caused by a deterioration of the ability of the lens to focus, making images look blurry when viewed close up. These changes occur at around 45 years of age, and the main symptom is the need to lengthen the reading distance, i.e. holding a book or newspaper further away.
But why does presbyopia occur?
The human eye at rest is focused to see well in the distance and close up. The curvature of the lens changes, so that the rays of light are focused on the retina. Presbyopia occurs when the lens loses this capacity, due to aging. As mentioned earlier, this type of refractive error appears at around the age of 45; however, myopic people may continue to have good close up vision for longer.
The current methods used to correct these vision changes are glasses with bifocal lenses or the most modern, progressive lenses. Refractive surgery may also be used; however its use in such cases is still being investigated.