What Is Long-sightedness Or Farsightedness? What Is Hyperopia?

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Main Category: Eye Health / Blindness
Article Date: 26 Feb 2010 - 0:00 PDT

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Hyperopia, also called farsightedness (far-sightedness), long-sightedness (longsightedness) or hypermetropia is a common vision defect in which the individual has difficulty focusing on near objects. In extreme cases of hyperopia the person can only focus on objects that are fairly far away - in very extreme cases focusing properly is not possible at any distance. The vision imperfection is usually caused by an eyeball that is too short, or a lens that is not round enough, probably because the cornea is too flat.

Farsightedness commonly affects people during middle age - during their 40s or 50s, but it may also be present from birth. The majority of children who are born with some degree of hyperopia tend to get better as they get older and their eyes develop.

According to the National Health Service (NHS), UK, approximately 13.2% of British people aged between 20 and 25 years have Hyperopia, and 17.4% have it in their early forties. According to the American Academy of Ophthalmology (AAO) over 12 million Americans age 40 and older are hyperopic.

According to Medilexicon's medical dictionary:

Hyperopia is " Long-sightedness; that optic condition in which only convergent rays can be brought to focus on the retina."

What are the signs and symptoms of hyperopia?

A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign. The following are the most common signs and symptoms of hyperopia:

• Objects nearby appear blurry
• The individual needs to squint (strain, narrow their eyes) to see clearly
• Headache or discomfort after prolonged reading or writing
• The person has eyestrain - burning or aching in or around the eyes

What are the causes of hyperopia?

The human eye has two focusing parts:

• The cornea - this is the clear front part of the eye that transmits and focuses light into the eye.
• The lens - this is a transparent structure inside the eye. It focuses light rays onto the retina (a layer of nerves at the back of the eye that senses light and creates impulses that are sent through the optic nerve to the brain).
• The optic nerve - the nerve that connects the eye to the brain; it carries impulses formed by the retina to the brain. The brain then interprets them as images.

An eyeball with an ideal shape should have a perfectly smooth curvature of the cornea and lens - similar in shape to the surface of a rubber ball. The cornea and the lens refract (bend) the incoming light rays so that an image is focused sharply on the retina.

A refractive error - light rays may not be refracted properly if the cornea and/or lens are not evenly and smoothly curved. Hyperopia is one type of refractive error. The cornea is either not curved enough, or the eye is shorter than it should be. The light rays do not focus on the retina, but behind it - the light rays travel to the back of the retina before they have been bent properly by the lens and cornea - resulting in blurry vision when objects are close. Some middle-aged people whose eyes gradually lose the ability to focus actively on close objects (presbyopic) may still be able to focus enough for nearby clarity.

People who are born with hyperopia may be able to focus on distant objects during childhood, however, eventually it may become more difficult to focus, and even distant objects may not be very clear.

Refractive errors may also cause myopia (short-sightedness, nearsightedness), or astigmatism.

Experts believe hyperopia may be an inherited condition.

In rare cases hyperopia may also be caused by:

• Diabetes
• Fovea hypoplasia (macular hypoplasia) - a rare medical condition involving the underdevelopment of the macula, a small area on the retina. Macular hypoplasia is often linked with albinism.
• Tumors

Diagnosing hyperopia

Long-sightedness is diagnosed by a standard eye exam. The following health care professionals deal with eye care:

• Ophthalmologist - a doctor who then went on to become an eye specialist. Eye surgery is carried out by an ophthalmologist.
• Optometrist - has a doctor of optometry (O.D.) degree. Most optometrists evaluate vision, prescribe corrective lenses and diagnose common eye disorders. Complex eye disorders are dealt with by an ophthalmologist.
• Optician - this person assembles eyeglasses, fits them and sells them. In some parts of the world they also sell and fit contact lenses. The optician fills prescriptions for eyeglasses.

A regular eye exam should include:

• Adults - the American Academy of Ophthalmology says that adults who do not wear eyeglasses or lenses and are not at higher risk of developing certain eye conditions should have an eye exam:
  
  At least once between 20 and 39 years of age
  About once every two to four years between the ages of 40 and 64
  About once every one or two years after the age of 65
  
  People who do wear glasses or contact lenses should have their eyes checked annually. Anybody who detects any problem or change in their vision should see an eye specialist immediately.
  
  Individuals who have a close relative with glaucoma should have their eyes checked every 3 to 5 years between the ages of 20 and 29.
• Children and teenagers - children should have their eyes checked by a pediatrician, or another specialized health care professional:
  
  Before they are 3 months old
  Between the ages of 6 months and 1 year
  When they are about 3 years old
  When they are about 5 years old
  
  If the child has vision problems or symptoms of eye trouble he/she should be checked more often. Children with underlying conditions that are linked to possible eye problems, such as diabetes, should also have more frequent eye tests.

Most eye conditions can be corrected successfully. However, if they are left untreated the risk of complications is much higher.

An eye test checks the patient's:

• Ability to focus on near objects
• General eye health - to determine whether there are any eye conditions or physical abnormalities
• Sharpness of distance vision

Snellen chart - in a basic test (visual acuity test) the patient reads letters from a Snellen chart. This chart is imprinted with block letters; each line has a smaller font size, corresponding to the distance at which that line of letters is normally visible.

Each block letter has been scientifically designed. The chart is named after Herman Snellen (1834-1908), a Dutch ophthalmologist.

If a patient wears prescription eyeglasses or contact lenses they may be asked to do the test with them on.

According to the National Health Service (NHS), UK, anybody who is unable to read the top line of the Snellen chart is eligible to register as blind or partially sighted. The patient's GP (general practitioner, primary care physician) will refer them to an ophthalmologist and contact their local social services department confirming that they have been diagnosed as blind or partially sighted. If patients are able to read the first three lines, but have a very restricted field of vision they may also be registered as partially sighted or blind in the UK.

The eye specialist also looks for signs of eye conditions by shining a light into the patient's eyes and observing their reaction. The health care professional will be looking out for such eye conditions as glaucoma or diabetic retinopathy.

What are the treatment options for hyperopia?

Hyperopia treatment aims to help light focus correctly on the retina - this may be achieved through corrective lenses or refractive surgery.

Corrective lenses - most young people with hyperopia do not need corrective lenses because they are able to compensate by focusing on near objects. However, by middle age, when the lenses are less flexible, the majority of people with long-sightedness need corrective lenses.

• Eyeglasses - these may include bifocals, trifocals and standard reading glasses.
• Contact lenses - these may be hard, soft, extended wear, disposable, RGP (rigid gas-permeable) and bifocal. Long-sighted individuals who have started to experience presbyopia may benefit from monovision contact lenses. A monovision contact works in only one eye, the less dominant one. Some people find monovision contacts difficult to adapt to.

Refractive surgery - in the majority of cases, refractive surgery is used for short-sightedness (nearsightedness, myopia). However, it can also be used for hyperopia. Examples include:

• LASIK (laser-assisted in-situ keratomileusis) - this is a type of laser eye surgery designed to alter the shape of the cornea. The ophthalmologist uses a keratome or a specially designed laser to make a thin, circular hinged cut (flap) into the cornea. An excimer laser is used to remove layers from the cornea's center, resulting in a steeper domed shape. The thin corneal flap is then put back into place. Excimer lasers do not produce heat.
• LASEK (laser-assisted subepithelial keratectomy) - the surgeon creates a flap on the epithelium (the thin protective cover of the cornea). An excimer laser is then used to reshape the outer layers of the cornea, steepening its curvature. The epithelial flap is then repositioned. After the operation the patient wears a bandage contact lens for a few days.
• PRK (photorefractive keratectomy) - in this case the epithelium is removed. Otherwise it is similar to the LASEK procedure. The epithelium eventually grows back, this time naturally into the cornea's new shape. After the operation the patient wears a bandage contact lens for a few days. Patients may find this procedure more uncomfortable than LASEK.
• CK (conductive keratoplasty) - uses radiofrequency energy to reshape the cornea and correct presbyopia. This procedure works by increasing the curvature of the cornea in a uniform fashion, adding more light bending power to the eye's optical system. A small probe is placed on the edge of the cornea - the probe applies radiofrequency energy to the corneal substance, causing the cornea around the probe to slightly shrink. The probe then goes in a ring pattern around the cornea, causing local shrinking immediately next to the ring pattern. The center of the cornea becomes more steeply shaped as a result. According to The Mayo Clinic, USA, Ck results are variable.

Laser surgery may not be suitable for:

• Patients with diabetes
• Pregnant and breastfeeding women
• Patients with weakened immune systems
• Patients with other eye problems, such as glaucoma or cataracts

What are the risks of laser surgery?

All surgical procedures have some risks. Laser surgery may result in the following rare complications:

• Worse post-operative vision - if the surgeon misjudges how much tissue to remove from the cornea the patient could end up with worse vision than before.
• Epithelia in-growth - this is when the surface of the cornea starts growing into the cornea itself. This can cause vision problems and may require additional surgery.
• Ectasia - the cornea becomes too thin. The patient's vision becomes worse (sometimes lost completely).
• Microbial keratitis - an infection of the cornea.

The National Institute of Clinical Excellence (NICE), a UK government body that approves National Health Service therapies, carried out a LASIK surgery study, and found that after surgery there was a:

• 0.6% chance of a correction error
• 1.3% chance of epithelial in-growth
• 0.2% chance of ectasia
• 0.16% chance of microbial keratitis

NICE adds that although LASEK and PRK data is not as comprehensive, the risk factors are thought to be similar.

What are the possible complications of hyperopia?

Hyperopia complications in adults are rare. If an adult finds the condition worsens, which is often the case with age, stronger eyeglasses or contact lenses are usually recommended to retain normal vision. Complications, when they do occur, tend to do so with children whose condition is left untreated.

• Strabismus - the eyes are not properly aligned with each other and focus on different things. This may make it harder to judge how far away objects are from you and in relation to each other (depth perception). The other eye may become weakened, leading to amblyopia.
• Amblyopia - one eye becomes dominant over the other, usually due to strabismus, cataracts, or some other eye condition. If a child uses mainly one eye to focus, there is a risk the other eye will gradually become weaker. If left untreated the patient may ultimately lose all vision in that eye.

Both strabismus and amblyopia are treatable. The child wears a patch over the stronger eye, encouraging the brain to take more notice of the weaker eye, making it stronger. Prescription eyeglasses may also be used to help align the eyes (so they both see the same thing at the same time). In severe cases realignment of the eyes and strengthening of the eye muscles may only be achieved with surgery.

Adults who develop hyperopia and do not get eyeglasses or contact lenses may find that their quality of life is undermined. There may also be more eyestrain, squinting, and headaches. If somebody cannot see properly there may also be safety implications.

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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