Far-sightedness lens correction
Hyperopia or hypermetropia, commonly known as farsightedness or longsightedness, is an abnormal eye condition whereby there is better visual acuity for objects in the distance than nearby. This results when incoming light rays enter the eye and converge behind the retina to create a blurred object, instead of converging directly on the retina to create a focused object.
This defect can be attributed to the length of the eye, if it is too short from front to back, or to the roundness of the lens, if it is not round enough. Both cause incoming light rays to pass through the retina before converging and thus cause the inability to focus on near objects. An extreme case of this defect of vision is the incapability to focus on objects at any distance. As an object moves towards the eye, the eye must increase its power to keep the image on the retina. If the power of the cornea and lens is insufficient, the image will appear blurred.
The phenomena of hyperopia highlights how remarkably the eye normally functions, whereby parallel light rays from an object, near or far, are bent as they pass through the curved lens and cornea precisely to converge on a point on the retina to give visual acuity. Many babies naturally have slight hyperopia that corrects itself as they grow older. Through human creativity, more pronounced defects in this remarkable system, such as hyperopia, can be corrected via corrective lenses, surgery, or other means.
The lens system of the eye is designed so that incoming, parallel light rays are bent to converge at a point behind the lens, ideally on the retina for perfect vision. In hyperopia, the point of focus of light rays coming from an object occurs behind the retina.
People with hyperopia can experience blurred vision, asthenopia, or fatigue of the eye, and accommodative dysfunction, or the inability of the eye lens to reshape in order to focus on near objects. In addition, a person may experience binocular dysfunction, amblyopia (better known as lazy eye), or even strabismus, where the eyes are misaligned and cannot focus on the same object at the same time, similar to crossed-eyes.
Hyperopia is often confused with presbyopia, another condition that frequently causes blurry near vision. Presbyopia is a natural age-related process which causes people in their mid-40s to experience vision problems, namely to close objects. This occurs because the lens begins to harden and become less flexible and able to adjust to focus objects up close, which is different from the cause of hyperopia, which is due to the shape of the eye. Like hyperopia, presbyopia also is sometimes referred to as farsightedness, since in otherwise normally-sighted persons it makes it more difficult to focus on near objects than on far objects.
Causes and symptoms of hyperopia
Hyperopia can be due to family history, and in some cases, can be outgrown due to the changing lens shape throughout the adolescent years. In extreme cases, diseases such as retinopathy, a nonimflammatory retina disorder, can also help cause hyperopia. Other examples include eye tumors and lens dislocation, which may also attribute to hyperopia.
Depending on the severity of hyperopia, an individual may experience a great number of symptoms to none at all. In extreme cases, close up and distant vision is impaired, where all objects are blurry. Other times objects are only out of focus for nearby objects. Headaches, aching eyes, burning, and eyestrain are the most common symptoms, especially when looking at objects up close. Children do not usually experience many symptoms. However, if a child continuously rubs his or her eyes, becomes cross-eyed, or has estropia (one eye points inward), or loses interest in reading, these could all be signs that the child may have hyperopia, and should be examined by an ophthalmologist.
Other signs of hyperopia include tearing, redness in the eye, squinting, facial contortions, rapid blinking, and decreased hand-eye coordination.
Classification of hyperopia
Hyperopia is typically classified according to clinical appearance, its severity, or how it relates to the eye's accommodative status.
Classification by clinical appearance involves three categories:
- Simple hyperopia—from normal biological variation
- Pathological hyperopia—from maldevelopment or ocular disease
- Functional hyperopia—from paralysis of accommodation.
Diagnosis, prevention, and treatment
Detection through normal eye exams or photo screening is usually the best method of detecting hyperopia. Visual acuity is affected according to the amount of hyperopia, as well as the patient's age, visual demands, and accommodative ability. In addition, static retinoscopy, subjective refraction, and autorefraction are procedures to measure refractive error.
Causes of hyperopia are usually found in early childhood and in most cases, a person outgrows such defects through normal adulthood development and lengthening of the eyeball; therefore, treatment depends heavily on the age of the patient.
Various eye care professionals, including ophthalmologists, optometrists, orthoptists, and opticians, are involved in the treatment and management of hyperopia. Minor cases 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 dioptric value, which causes the light to focus closer than its normal range. For very severe cases, options such as laser surgery (H-LASIK), photorefractive keratectomy (H-PRK), or intraocular lens implants (IOLs) exist. Hyperopia is sometimes correctable with various refractive surgery procedures.
Simple lifestyle changes can help ease common symptoms, such as creating an environment with better lighting, reducing glare, and even taking care of visual hygiene. In some aspects, pharmaceutical treatments such as anticholinesterase agents can be prescribed.
There are various alternative treatments that have been used for hyperopia. These include using such herbal medicines as bilberry (Vaccinium myrtillus) to increase blood flow through the vessels of the eye, eyebright (Euphrasia officinalis) to relieve eye-strain, and schisandra (Schisandra chinensis) to improve visual acuity. Ayurveda treatments include head massage and placing drops in the nose using warm Jivantal taila oil, and Chinese traditional medicine involves performing various eye exercises, which have been shown to reduce hyperopia in children. The Bates method involves therapeutic eye exercises to strengthen and train the eye muscles (although this has not been tested clinically) and some advise supplements such as zinc, vitamin A, vitamin C, magnesium, and selenium to strengthen the retina and improve vision.
- B. Rowland and T. G. Odle, "Hyperopia," in J. L. Longe, The Gale Encyclopedia of Alternative Medicine (Farmington Hills, MI: Thomson/Gale, 2005, ISBN 0787693960).
- American Optometric Association Optometric clinical practice guideline: Care of the patient with hyperopia. American Optometric Association (1997). Retrieved August 30, 2016.
- Cleveland Clinic and C. D. Haines. Eye health: Presbyopia and your eyes, WebMD. Retrieved August 30, 2016.
- K. Tsubota, B. S. Boxer Wacher, D. T. Azar, and D. D. Koch (eds.), Hyperopia and Presbyopia (New York: Marcel Dekker, 2003, ISBN 0824741072).
- Longe, J. L. The Gale Encyclopedia of Alternative Medicine. Farmington Hills, MI: Thomson/Gale, 2005. ISBN 0787693960
- Tsubota, K., B. S. Boxer Wacher, D. T. Azar, and D. D. Koch (eds.). Hyperopia and Presbyopia. New York: Marcel Dekker, 2003. ISBN 0824741072
All links retrieved January 23, 2018.
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