Age-related long-sight (presbyopia) is a normal part of ageing and is not a disease. As you get older, you find it more difficult to see (focus on) near objects. The problem can be corrected by wearing reading glasses or contact lenses. Presbyopia is a type of sight problem called a refractive error.
What is presbyopia?
Presbyopia is long-sight (hypermetropia), caused by age.
In order to see close-up objects, our eyes have to accommodate. This means that the lens changes its thickness. Its thickness is adjusted by the ciliary muscles that attach to the suspensory ligaments at either end. As these muscles tighten, the ligaments lengthen and the lens becomes more thickened and curved. Light rays from close objects are brought into sharp focus on the retina.
As we become older the lens becomes more stiff and less elastic. This makes it more difficult for the lens to change shape - the ciliary muscles have to work harder to make it do so. Eventually they are unable to do this at all and the lens cannot be thickened. With the lens in its normal resting position you are still able to focus on objects in the distance - long sight. However, because the lens cannot thicken, it cannot manage the extra degree of focus (accommodation) which is needed for near objects.
There are five types of presbyopia:
- Incipient presbyopia. This is the very earliest stage, when it may be a bit more difficult to read small print.
- Functional presbyopia. This occurs when you begin to notice more problems with near sight.
- Absolute presbyopia. If you have this type, your eyes cannot focus on near objects at all.
- Premature presbyopia. This term is used when presbyobia occurs before the age of 40 years.
- Nocturnal presbyopia. When this occurs, focusing on near objects is particularly difficult in low light conditions.
What is a refractive error?
A refractive error is an eyesight problem. Refractive errors are a common reason for reduced level of eyesight (visual acuity).
Refraction refers to the bending of light, in this case by the eye, in order to focus it. A refractive error means that the eye cannot focus light on to the retina properly. This usually occurs either due to abnormalities in the shape of the eyeball, or because age has affected the workings of the focusing parts of the eye.
There are four types of refractive error:
- Short sight (myopia).
- Long sight (hypermetropia).
- Age-related long sight (presbyopia).
- Astigmatism (a refractive error due to an unevenly curved cornea).
In order to understand refractive errors fully, it is useful to know how we see.
When we look at an object, light rays from the object pass through the eye to reach the retina. This causes nerve messages to be sent from the cells of the retina down the optic nerve to the vision centres in the brain. The brain processes the information it receives, so that in turn, we can see.
Light rays come off an object in all directions, as they result from the light around us from sun, moon and artificial light bouncing back off the object. The part of this bounced light that come into the eye from an object needs to be focused on a small area of the retina. If this doesn't happen, what we look at will be blurred.
The cornea and lens have the job of focusing light. The cornea does most of the work, as it (refracts) the light rays which then go through the lens, which finely adjusts the focusing. The lens does this by changing its thickness. This is called accommodation. The lens is elastic and can become flatter or more rounded. The more rounded (convex) the lens, the more the light rays can be bent inwards.
The shape of the lens is varied by the small muscles in the ciliary body. Tiny string-like structures called the suspensory ligaments are attached at one end to the lens and at the other to the ciliary body. This is a bit like a trampoline with the central bouncy bit being the lens, the suspensory ligaments being the springs and the ciliary muscles being the rim around the edge.
When the ciliary muscles in the ciliary body tighten, the suspensory ligaments slacken, causing the lens to become fatter. This happens for near objects. For looking at far objects, the ciliary muscle relaxes, making the suspensory ligaments tighten, and the lens thins out.
More bending (refraction) of the light rays is needed to focus on nearby objects, such as when reading. Less bending of light is needed to focus on objects far away.
Age-related long sight is caused by normal ageing. It usually begins at around 40 years of age. By the age of 45 years, most people will need reading glasses. If you already wear glasses or contact lenses, your prescription may alter as a result of age-related long sight.
Age-related long sight may develop at a younger age if you already have long sight (hypermetropia). People who have a job that requires a lot of close-up work and people who live and work in a hot climate with lots of ultraviolet sunlight exposure are also at higher risk of premature age-related long sight.
What are the symptoms of age-related long sight (presbyopia)?
Initial symptoms may be difficulties with prolonged close-up work, with tiring (eye strain) of the eyes. This may be worse in dim light. You may also notice difficulty in adjusting vision if you look quickly from a near object to a faraway one. This may progress to blurred vision when looking at objects close up and to headaches and eye strain when attempting close work.
Age-related long sight can be corrected by wearing reading glasses. If you already have glasses, bifocal or varifocal lenses may be prescribed to treat your age-related long sight. With these lenses, different parts of the lens are different prescriptions.
Bifocal ('bi' means two) lenses have a lens at the bottom for long sight (to allow close-up vision) and the rest of the lens above (allowing distant vision). Multifocal lenses have at least three focus 'zones' - for distant, middle and near vision, with gradual changes between them. Middle vision is best imagined as that needed for computer screen work
For people who already have contact lenses, reading glasses may be prescribed in addition to these. Another option is bifocal contact lenses, or wearing a different contact lens in each eye - one to allow near vision, the other for distance vision. The price of correcting one eye (effectively to make it slightly short-sighted) is some loss of distance vision in that eye - but the other eye retains good distance vision. Usually the two eyes adapt to the differences between them, so that the patient can see near and far equally well. Distance vision can be slightly compromised - and some patients notice 'ghosting' (faint double vision) on distant objects which does not always resolve with time.
Newer developments in laser eye surgery mean that various non-NHS options are now offered for age-related long sight. Some of these work on the principle of correcting one eye for near vision, whilst correcting the other eye to give good distant vision:
Kamra® corneal inlay
The Kamra® corneal inlay was approved in 2015. The inlay is designed to eliminate the need for reading glasses among people between the ages of 45 and 60 years who have good distance vision without glasses but have problems seeing up close due to age-related long sight.
The inlay is a small, thin opaque device with a tiny opening in the centre. It is surgically implanted in the central cornea, directly in front of the pupil of the eye. The central opening in the inlay creates a 'pinhole camera' effect. This effect, also seen if you look through a pinhole in a piece of paper, sharpens near vision while maintaining clear distance vision.
The inlay typically is implanted in the non-dominant eye. This allows both eyes to be used for distance vision, while the inlay sharpens near vision in the non-dominant eye. The procedure takes around 15 minutes and can be performed in the treatment room. No stitches are needed. Healing time may vary but most people are able to resume their normal activities within 24-48 hours.
LASIK® stands for Laser-Assisted In situ Keratomileusis. This is the most popular form of laser eye surgery and is a means of altering the refractive power of the cornea. In monovision LASIK® for long sight this is essentially done for one eye only:
- The laser is used to lift and remove a thin flap of the cornea.
- This helps to flatten the cornea so that the light rays can be focused further back, and on to the retina.
- The flap is then replaced and sticks spontaneously to the underlying cornea. The flap serves as a natural bandage, keeping the eye comfortable as it heals. Healing occurs relatively quickly.
- This is the most popular and common type of laser eye surgery.
- Vision recovery time is said to be around 24 hours.
The LASIK® surgeon fully corrects the distance vision of one eye (usually the dominant eye), and intentionally makes the non-dominant eye mildly nearsighted. The newly nearsighted eye sees near objects clearly without glasses, although its distant vision may be less good. So, after monovision LASIK®, the dominant eye takes the lead to provide clear distance vision and the non-dominant eye is responsible for sharpening near vision. If additional distance vision clarity is desired for specific activities after monovision LASIK®, special-purpose eyeglasses or contact lenses can be prescribed that optimise distance vision.
Monovision conductive keratoplasty (CK)
CK uses low-level, radiofrequency energy to shrink fibres in the edge of the cornea to increase the curve and therefore increase its focusing power. Like monovision LASIK® one eye is corrected for close vision and the other left for distance vision.
Monovision of any kind, whether it's monovision LASIK® or monovision with contact lenses, involves some compromise and not everyone adapts well to it. It's a good idea to try monovision with contact lenses before committing to a permanent surgical procedure, in case you are one of the small minority who don't adapt to it.
Refractive lens exchange (RLE)
RLE is the removal and replacement of the eye's natural lens with an artificial lens to improve vision. The procedure is very similar to cataract surgery.
RLE can reduce the need for reading glasses while providing clear distance vision without glasses. It is particularly helpful for patients with age-related long sight who are developing cataracts.
How often do I need an eyesight test?
This depends on your age, your family history and any pre-existing medical conditions.
People at high risk of sight problems need more frequent eyesight checks. If you have diabetes, raised pressure in the eye (glaucoma), macular degeneration, or a family history of these conditions, you should check to see what your optician recommends about regular check-ups.
If you fall into a high-risk group, you should have at least a two-yearly (biennial) eye examination if you are over 50 years of age, and a yearly (annual) one if you are over 60 years of age.
If you have more than one risk factor then an eyesight check is recommended at least every three years once you reach 40 years of age.
Low-risk people with no symptoms of an eyesight problem, do not need to have their eyes tested so frequently. If you fall in this group and are aged between 19 and 40 years, an eye test is needed every 10 years. Between the ages of 41 and 55 years, it is recommended that you see an optician every five years. At any age between 56 and 65 years, two-yearly checks are needed, dropping to annual checks in low-risk people who are aged 65 years or more.
Further reading and references
Corneal inlay implantation for correction of Presbyopia; NICE Interventional Procedure Guidance, April 2013
Laser correction of refractive error following non-refractive ophthalmic surgery; NICE Interventional Procedure Guidance, March 2011
Standards for laser refractive surgery; Royal College of Ophthalmologists (May 2009)
Laser Refractive Surgery; Royal College of Ophthalmologists
Torricelli AA, Junior JB, Santhiago MR, et al; Surgical management of presbyopia. Clin Ophthalmol. 20126:1459-66. doi: 10.2147/OPTH.S35533. Epub 2012 Sep 6.
Barisic A, Gabric N, Dekaris I, et al; Comparison of different presbyopia treatments: refractive lens exchange with multifocal intraocular lens implantation versus LASIK monovision. Coll Antropol. 2010 Apr34 Suppl 2:95-8.
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