Hyperopia lens correction
|Classification and external resources|
Hyperopia or hypermetropia, from the Greek word "hyper-metropia : ὑπερ-μετρωπία" (hyper = over + metro = measure + op = sight, look + suffix ia = condition, state > thus a condition of over-measured sight) commonly known as farsightedness (American English) or longsightedness (British English), is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or the lens cannot become round enough), causing the eye to not have enough power to see in the distance, causing the eye to have to accommodative, by having to make the lens of the eye more convex, or plus. For near objects, the eye has to accommodate even more. Depending on the amount of hyperopia and the age of the person which directly relates to the eye's accommodative ability, the symptoms can be different.
People with hyperopia can experience blurred vision, asthenopia, accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus,  The causes of hyperopia are typically genetic and involve an eye that is too short or a cornea that is too flat, so that images focus at a point behind the retina.
Signs and tests
A farsighted person, depending on the amount of hyperopia and age, would have trouble reading the Snellen distance chart, can see the Snellen chart, but complain of near vision problems, or can see the Snellen chart and near work, but complain of eye strain.
A general eye examination, or standard ophthalmic exam may include the following points;
- Eye pressure measurement (Tonometry)
- Refraction test, to determine the correct prescription for glasses
- Retinal examination
- Slit-lamp exam of the structures at the front of the eyes
- Test of color vision, to look for possible color blindness
- Tests of the muscles that move the eyes
- Visual acuity at a distance, using the Snellen Chart
Cycloplegic Refraction, to determine the full amount of hyperopia by applying paralyzing eye drops to the eye to stop accommodation.
Farsightedness is the result of the visual image being focused behind the retina rather than directly on it. It is mainly caused by two reasons-
- Low converging power of eye lens because of weak action of ciliary muscles.
- Eyeball being too short because of which the distance between eye lens and retina decreases.
Farsightedness is often present from birth, but children have a very flexible eye lens, which helps make up for the problem. As aging occurs, glasses or contact lenses may be required to correct the vision. Farsightedness is hereditary.
- Simple hyperopia
- Pathological hyperopia
- Functional hyperopia
The causes are that low converging power of eye lens and the distance between eye lens and retina increases.
In severe cases of hyperopia from birth, the brain has difficulty in merging the images that each individual eye sees. This is because the images the brain receives from each eye are always blurred. A child with severe hyperopia can never see objects in detail and might present with amblyopia or strabismus. If the brain never learns to see objects in detail, then there is a high chance of one eye becoming dominant. The result is that the brain will block the impulses of the non-dominant eye with resulting amblyopia or strabismus. In contrast, the child with myopia can see objects close to the eye in detail and does learn at an early age to see detail in objects.
The child with hyperopia will typically stand close to a television. One would have expected that the child would stand far away because the child is hyperopic, but because the brain has never learned to see detailed lines and object contours the child sees objects blurred. While children with myopia learn to see sharp lines because they can see perfectly well very close to their eyes, the brain of a child with hyperopia cannot see sharp lines, so they stand right in front of the television to at least see blurred images. This blurred vision may also cause a child to develop a squint because the two eyes do not detect sharp lines which the brain can use to map the separate images of the two eyes together to form a single image. Each eye functions independently. So a child with hyperopia from birth presents with decreased visual perception.
The parents of a child with hyperopia do not always realize that the child has a problem at an early age. A hyperopic child might have problems with catching a ball because of blurred vision and because of a decreased ability to see three-dimensional objects. The child will typically perform below average at school. As soon as a child starts identifying images, a parent might find that the child cannot see small objects or pictures.
In many circumstances mild to moderate hyperopia can be mistaken for ADHD; or other learning and personality disorders. One coping mechanism many children subconsciously use is constant head and body movement to attempt to maintain focus. The incidence of hyperopia is correlated with lower IQ, educational attainment, and literacy.  This is to be contrasted with myopia, which is associated with higher IQ and educational outcomes.
Various eye care professionals, including ophthalmologists, optometrists, orthoptists, and opticians, are involved in the treatment and management of hyperopia. At the conclusion of an eye examination, an eye doctor (ophthalmologist or optometrist) may provide the patient with an eyeglass prescription for corrective lenses. Minor amounts of hyperopia are sometimes left uncorrected. However, larger amounts may be corrected with convex lenses in eyeglasses or contact lenses. Convex lenses have a positive optical power, which causes the light to focus closer than its normal range.
- American Optometric Association. Optometric Clinic ef_error_pres.htm "Refractive Error and Presbyopia." Refractive Source.com Accessed September 20, 2006.
- American Optometric Association. Optometric Clinical Practice Guideline: Care of the patient with presbyopia. 1998.
- Czepita D., Lodygowska E., Czepita M. (2008). "Are children with myopia more intelligent?" (PDF). Annales Academiae Medicae Stetinensis 54 (1): 13–16. PMID 19127804.
- USAEyes, Council for Refractive Surgery Quality Assurance"Hyperopia (Farsighted-Longsighted) Correction." Accessed August 18, 2012.
- Scottish Sensory Centre - Medical Info on Hypermetropia
- LASIK - Medical Info on refractive disorders by eMedicine
- Farsightedness by EyeTopics