Long Sight (Hypermetropia)
The medical name for long-sight is hypermetropia, sometimes called hyperopia. Eyesight problems, such as hypermetropia, are also known as refractive errors. Long sight leads to problems with near vision and the eyes may commonly become tired. Distance vision (long sight) is, in the beginning, good. Long sight can be corrected by glasses or contact lenses, or sometimes 'cured' with laser eye surgery.
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.
What is long sight (hypermetropia)?
Long sight occurs when light from near objects is not quite brought to focus in time to hit the retina. The point of focus would in fact be behind the retina, if the light could get that far. The lens tries hard to change its thickness (becomes fatter or more rounded) in an attempt to bring the light into focus on the retina - a process called accommodation. However, people with long sight cannot accommodate fully and so the light does not focus on the retina and vision is blurred. This occurs because the eyeball is too short, the cornea is too flat (and so bends the light rays less), or the lens cannot become round enough (and so lacks power).
People with a minor degree of long sight can usually see at distance, as this light does not require the same strength of focusing. Their near sight may also be clear. However, they may get tiring of the eyes, often with a headache and vision discomfort, because the lens is having to work so hard. People with more severe hypermetropia are not able to see near objects clearly in focus. Long sight means exactly what the term suggests: you can see objects which are a long distance from you quite clearly.
The diagram above shows the differences in focusing between a normal and a long-sighted (hypermetropic) eye:
What causes long sight (hypermetropia)?
The causes of long sight are usually hereditary (genetic). Long sight can occur at any age but it tends to become more noticeable above the age of 40 years.
In rare cases, long sight is caused by other conditions such as diabetes, small eye syndrome (microphthalmia), cancers around the eye and problems with the blood vessels in the retina.
Many babies and very young children tend to be slightly long-sighted but usually grow out of this by about 3 years of age.
A particular type of age-related long sight (presbyopia) occurs because the lens of the eye becomes more stiff with age. See separate leaflet called Age-related Long Sight (Presbyopia) for more details.
What are the symptoms of long sight (hypermetropia)?
The main symptom is a difficulty with near vision. 'Tiring' of the eyes (asthenopia) is common and long-sighted people may have headaches and uncomfortable vision.
There may be difficulties with seeing with both eyes (binocular vision), as the brain will tend to ignore signals coming from the most long-sighted eye. Lazy eye (amblyopia) or squint (strabismus) can therefore also occur in long sight.
Long-sighted people may have difficulty with depth perception (3-dimensional vision), as this needs two eyes to work together, more or less equally.
Are there any complications?
If severe long sight (hypermetropia) is present from a very young age, lazy eye (amblyopia) can result. The eye with less good vision does not learn to see properly because the brain ignores its signals and concentrates only on the better eye. Visual development in the brain occurs in the first few years of life and if this problem is not spotted until after vision has finished developing, the poorer eye will not fully develop its 'information route' into the brain, so will never see as well.
What is the treatment for long sight (hypermetropia)?
The simplest, cheapest and safest way to correct long sight is with glasses. Convex prescription lenses (called plus lenses) are used to bend light rays slightly inwards to give a little bit of additional focusing power to the eye. The light rays then have a lesser angle to bend travelling through the cornea and lens and the lens has less work to do. As a result, the light rays are able to focus on the retina. There is an enormous choice of spectacle frames available, to suit all budgets; younger people may even regard them as a fashion accessory.
These do the same job as glasses but they sit right on the surface of the eye. Many different types of contact lenses are available. Lenses may be soft or rigid gas-permeable. They can be daily disposable, extended wear, monthly disposable, or non-disposable. Your optician can advise which type is most suitable for your eyes and your prescription.
Contact lenses tend to be more expensive than glasses. They require more care and meticulous hygiene. They are more suitable for older teenagers and adults, rather than very young children.
Laser eye surgery is an option for some people with long sight. Generally, this type of surgery is not available on the NHS. Laser eye surgery is expensive but offers the chance to restore normal sight permanently. The procedure is generally painless.
Complete and permanent resolution of the refractive error is possible in a number of people. Others have a significant improvement even though perfect vision is not achieved and glasses or contact lenses may still be needed.
A small number of people develop complications. Some develop hazy vision, a problem with night vision, or problems with bright light haloes in their peripheral (edge) vision.
Many private companies advertise laser eye surgery. Before embarking upon this type of treatment you should do some research. You only have one pair of eyes and you need to find the best treatment for you. This may not be the cheapest. Try to go with personal recommendations, preferably a recommendation by an NHS eye surgeon (ophthalmologist). It is important that you know your facts - the failure rate, the risk of complications, level of aftercare and what the procedure involves, before submitting yourself to an irreversible, costly treatment.
Several types of laser surgery have been developed. These include: LASIK®, PRK® and LASEK®. They are all similar, typically taking about ten minutes per eye and aiming to reshape the cornea by using the laser to remove a very thin layer of corneal tissue. The reshaping of the cornea allows the refraction of the eye to be corrected.
- LASIK stands for Laser-Assisted In situ Keratomileusis. This is the most popular form of laser eye surgery.
- 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.
For people who are not suitable for LASIK® the following two options are sometimes offered.
- PRK stands for Photo-Refractive Keratectomy.
- During PRK®, instead of creating a corneal flap as in LASIK®, the surgeon completely removes the extremely thin outer layer of the cornea, using an alcohol solution, a 'buffing' device or a blunt surgical instrument. The underlying cornea is then reshaped with a laser. A new epithelial layer grows back within five days.
- The healing time in PRK® is faster than in LASEK®.
- LASEK stands for LAser Sub-Epithelial Keratomileusis.
- The LASEK® procedure involves taking a thinner flap of corneal epithelium than in LASIK®. The cornea underneath is then treated as in LASIK® and the thinner flap is repositioned and held in place with a bandage contact lens.
- The hinged flap made in LASEK® surgery is much thinner than the corneal flap created in LASIK® (which contains both epithelial and deeper stromal tissues).
- The LASEK® technique lessens the likelihood of removing too much cornea. There is also slightly less risk of developing dry eyes afterwards.
- Patients with a naturally thin cornea may be more suited to this treatment.
- LASEK® can be a better option for patients with a high degree of long sight, which requires more tissue removal from the central cornea.
- LASEK® tends to be more painful and discomfort can last longer than with LASIK®. Visual recovery time can be up to a week.
- In some cases, the thin flap created during LASEK® is not strong enough to be replaced and will be removed completely as it would have been in PRK®.
- The alcohol solution used during LASEK® can irritate and slow the healing process immediately after surgery.
Side-effects of all laser surgery may include blurred vision, over-correction or under-correction of long-sight, eye infection and dry eyes.
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 five-yearly. 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 & references
- Settas G, Settas C, Minos E, et al; Photorefractive keratectomy (PRK) versus laser assisted in situ keratomileusis (LASIK) for hyperopia correction. Cochrane Database Syst Rev. 2012 Jun 13;6:CD007112. doi: 10.1002/14651858.CD007112.pub3.
- Standards for laser refractive surgery; Royal College of Ophthalmologists (May 2009)
- Photorefractive (laser) surgery for the correction of refractive error; NICE Interventional Procedure Guidance, March 2006
- Corneal inlay implantation for correction of Presbyopia; NICE Interventional Procedure Guidance, April 2013
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Katrina Ford
Dr Mary Lowth
Dr Colin Tidy