‘Presbyopia’ may sound like a disease but it is, in fact, a natural part of the ageing process of the eye. The word ‘presbyopia’ is derived from the Greek terms ‘presbys’ (‘old man’) and ‘ops’ (eye). Most people notice the effects after the age of 40 years, with symptoms worsening over time.
When a young child plays with a toy at close range, the lens within their eye changes thickness (accommodates) to focus light on the back of their eye so they can see the toy clearly. As the eyes age, this focusing ability slows and reduces as the lens becomes less elastic and able to change shape. When a person requires additional help to focus light on the back of the eye and improve their near vision, it is termed ‘presbyopia’. The spectacle prescription of a person with presbyopia will show an ‘addition’ or ‘add’. The power typically ranges between +0.75 and +3.50, and gradually increases with age. Keep in mind that this is different from their ‘spectacle prescription’ which tells them whether they are short-sighted or long-sighted.
How does presbyopia affect vision?
A person with presbyopia has difficulty focusing close-up (e.g. reading, computer work). Telltale signs are when a person holds things further away in an attempt to see them more clearly or complains that their ‘arms aren’t long enough!’ In early stages, they may complain of tired and strained eyes, with difficulty changing focus from near to far and vice versa, and in particular, after doing long periods of close-up work. Over time, they will start to experience blurring of their reading vision, particularly in dim light conditions and when viewing low contrast detail (e.g. a restaurant dinner menu). As presbyopia advances, this will also affect their ability to see things at further distances such as their computer screen. While it is logical that older people are more likely to notice the effects of presbyopia, their ability to see things in the close range varies depending on their spectacle prescription. For example, a 60-year old with a +2.50 presbyopic power may experience the following:
- If they are short-sighted – by definition, they can see clearly at a point in their close range without wearing spectacles. If they have mild short-sightedness (e.g. -2.00), they may be able to read comfortably and clearly at arm’s length. However, with high short-sightedness (e.g. -10.00), this clear focus point becomes uncomfortably close to the eyes at a distance of 10cm! This means they will need additional help to give them clear vision at a more comfortable reading distance.
- If they are long-sighted – they will experience blurred vision both in the close range and at far distance (depending on the extent of their long-sightedness).
How can it be corrected?
Presbyopia can be treated by spectacles (reading or varifocal/ bifocal spectacles), contact lenses (multifocal or monovision) or refractive surgery (laser, lens implant or other).
- Blended Vision and Monovision
If you are short-sighted, it is possible to correct the dominant eye fully for good distance vision and partially correct the non-dominant eye to leave some residual short-sightedness to help with reading vision. This strategy is known as ‘mono’ or ‘blended’ vision and provides freedom from spectacles most of the time. Many patients have already, very successfully, used the blended vision / monovision strategy with their contact lenses. If not, we would always advise a contact lens trial period intended to simulate the ‘mono’ or ‘blended’ vision effect before their laser surgery.
There is another solution to help with your reading addition – multifocal intraocular lens implants or IOLs. They are given the name ‘multi’-focal as they aid distance, intermediate and close reading vision (to a degree). They are premium correcting lens implants which are not available on the NHS and have become popular in recent years for the treatment of presbyopia. These lenses can usually be well tolerated and can give reasonably good distance and close vision, with a greater depth of focus than monofocal (‘mono’ focal – singular correction for distance only). However, this is sometimes at the expense of image quality. Glare and haloes may be troublesome. We would not recommend multifocal IOLs for professional drivers, those who drive frequently at night or those with very exacting visual requirements.
“Wearing reading spectacles will make my eyes worse. I can exercise my eyes instead.” This is untrue – presbyopia is not caused by muscle weakness but is the result of structural change in the lens and muscles inside the eyes. There are no exercises to overcome the effects.
The earliest recorded reference to presbyopia was found in 100 AD by Plutarch. “Pince-nez” reading spectacles, designed to be held in place by hand or by pressure on the nose were introduced around the 15th century mark, but it was an American scientist, Benjamin Franklin, who made a major breakthrough by inventing the bifocal – a way to avoid needing to swap between distance and reading spectacles.