Presbyopia affects everyone as part of the natural ageing process of the eye. Our eyes slowly lose the ability to focus on near objects. When light enters the eye, it passes through the cornea and pupil. The iris, the coloured part of the eye forms a ring around the pupil which opens and closes to adjust the amount of light entering the eye. The crystalline lens which sits behind the pupil in its healthiest state will change shape to ensure the light entering the eye is focussed perfectly onto the retina and thus allowing for clear vision at a range of distances. However, with age, the crystalline lens becomes progressively less flexible thus cannot change shape and therefore is unable to focus light correctly onto the retina. This results in a gradual deterioration of your ability to see near objects clearly, such as reading.
Risk Factors for Presbyopia
The most significant risk factor is age. The progressive loss of flexibility in our crystalline lens normally starts to affect us by age 40, and will affect everyone but some people notice it earlier than others. Certain disease can cause premature presbyopia in individuals younger than 40. In such causes careful examination is required to rule out the potential underlying cause of premature presbyopia, which includes:
- Cardiovascular disease
- Multiple Sclerosis
- Myasthenia Gravis
- Eye Trauma
Symptoms of Presbyopia
Signs of presbyopia typically involve a slow and gradual deterioration of your ability to focus on near objects, read small print and generally detailed close work. In most people these symptoms occur around age 40 onwards and include:
- Difficulty reading small print
- Fatigue when doing close work
- Eyestrain or headaches after reading or doing close work
- Having to hold reading material at arm’s length to keep it clear
- Inability to focus on objects near to you
- The need for brighter lighting when reading
Hyperopia has similar symptoms to presbyopia; however they are two distinct conditions. In both cases distance vision usually remains clear, but closer objects appear blurred. Hyperopia occurs when the eye is smaller or shorter than normal, or when the cornea is too flat thus underpowered. In this case light entering the eye is focussed behind the retina and thus near objects appear blurred as with presbyopia. However hyperopia is usually present at birth while presbyopia develops with age. Therefore it is possible to by hyperopic then develop presbyopia in your 40’s.
Presbyopia can combine with:
Treatment of Presbyopia
No cure exists for presbyopia; however there are a variety of options to correct this refractive error. Simple reading spectacles can be prescribed to allow us to read normally again. Great care should be taken when considering whether to buy over-the-counter reading spectacles from a pharmacy. ‘Ready Readers’ are made in powers ranging from +1.00 to +3.50 normally in +0.25 or +0.50 steps. The prescription remains equal in both eyes and the optical centre of the lens pre-defined by the manufacturer. ‘Ready Readers’ are not made specifically to your prescription, balancing your left and right eyes, correcting astigmatism, centred for your eye position or offering a wide selection of frames to best fit your face. Prescribed reading spectacles made to measure to your personal prescription in frames fitted for your face by a qualified dispensing optician will offer much clearer more comfortable vision in the vast majority of cases.
Bifocals can also be used to corrected presbyopia. Bifocals have two areas of correction with a clear visible line between the two. The lower portion is set for reading and close work and the upper portion is normally set for distance vision.
Progressive lenses or varifocals are commonly used to correct presbyopia. These lenses are similar to bifocals in that they offer more than one area of focus, but unlike bifocals there is no line. They offer a more gradual transition between distance vision and near vision, allowing clear vision from as far away as you can see, to reading distance and every distance in between.
Trifocals can be used but are rarely used nowadays due to the success of varifocals. Trifocals work in exactly the same manner as bifocals but offer three different points of focus. The portions are normally set for reading, mid-range and distance.
Contact Lenses can be used to successfully manage presbyopia in a number of ways. Multifocal contact lenses are available which offer clear distance and near correction within one lens, similar to a varifocal spectacle. These are now available in daily, two weekly and monthly formats. Bifocal contact lenses are available and work in a similar way to bifocal spectacles. Bifocal contact lenses have largely been replaced by multifocal contact lenses. Monovision contact lenses can be used which involves wearing a contact lens set for distance in one eye and a contact lens set for reading in the other eye. Modified monovision can also be utilised which involves wearing a multifocal or bifocal lens in one eye and a regular single vision lens in the other.
Outlook for presbyopia
The vision lost by presbyopia can be corrected with spectacles, contact lenses or in some cases surgery. The slow and gradual decline of the elasticity of the crystalline lens required to focus on near objects continues until about 65, when most of the elasticity is gone.
How to delay presbyopia:
- Wear protective spectacles or sunglasses to ensure optimal UV light protection
- Avoid trauma or injury to the eye by wearing relevant protective eyewear
- Eat a healthy diet with foods containing antioxidants, vitamin A, Beta Carotene and Omega III.