Hyperopia

Introduction

Hyperopia also known as hypermetropia long-sightedness or far-sightedness affects a person’s ability to see objects close to them. Vision problems such as long – sightedness are often referred to as refractive errors, if you are long – sightedness you will usually be able to see distance objects clearly, but nearby objects will be out of focus your eyes may also get tired easily. Hyperopia is one of the abnormal states that are most common with patient of refractive errors. Refraction is the bending of light rays as they pass through media of different optical densities. In normal vision, this occurs so that images are focused on the retina.

According to Money (2015), Hyperopia is refractive error whereby parallel rays of light are brought to a point focus behind the retina. Far – sightedness occur if your eyeball is too short or the cornea has little curvature, so light entering your eye is not focus correctly. As an object move towards the eyes, the optical power must increase to keep the image in focus on the retina if the power of the cornea and lens is insufficient, as in hyperopia, the image will appear blurred. Hyperopia is often corrected with prescription glasses or contact lenses. In some cases, laser surgery is also an effective treatment option.

 Causes

There are various causes of long – sightedness or hyperopia including age, genetics, natural, action of drugs and certain underlying medical conditions.

1. Age: Hyperopia or long – sightedness can occur at any age, but it is often more noticeable after the age 40. Age related long – sightedness is known as presbyopia. It develops when the lens in your eye become stiffer.
2. Genetics: Hyperopia or long-sightedness is thought to be a condition that some people inherit from their parents. However, with the exception of a rare form of hyperopia called nanophthalmos, specific genes for long-sightedness have yet to be identified and further research is needed.
3. Natural cause: This is mainly due to the smallness of the eyeball. The axial length of the eye may be too short for the focusing system resulting in the point of focus falling behind the retina. On the other hand, hyperopia could be seen as a condition that may result from the hypo – activity of the refractive mechanism. i.e. a situation where the principal refractive components together with the accommodative system lack sufficient plus power to ensure that the focal point is shifted forward onto the retina plane. Hyperopia also occurs when the cornea is not curved enough (it’s too flat) and when the lens is unable to become round enough.
4. Action of drugs: While on medication some drugs could temporarily induce refractive error like hyperopia or myopia in an emmetropic eye, (e.g. miotic eye drop like pilocarpine) due to its parasympathomimetic actions on accommodation. But the condition would revert to its normal state after the effect of the drug has been eliminated from the system.

 Underlying conditions

In rare cases, long-sightedness caused by these:

1. Diabetes: When there is too much glucose in the blood.
2. Microphthalmia (small eye syndrome) when a baby’s eyes do not develop properly during pregnancy. It is important for children to have regular eyes tests, because children are sometimes born long – sighted. The problem usually corrected itself as the child’s eyes develop.But long – sightedness that does not correct itself can lead to other eye related problems.
3. Fovea hyperplasia: When there is problem with the blood vessels in the retina.

 Classification of  hyperopia

Hyperopia is typically classified according to clinical appearance, its severity or how it related to the eye’s accommodative status.

1. Latent hyperopia: This is the amount of hyperopia that is constantly being compensated for by the ciliary muscles. This type of hyperopia is conceal or hidden and it can be corrected physiologically by the tonicity of the ciliary muscles. In other words, latent hyperopia could be regarded as the amount of hyperopia revealed by the use of a cycloplegicrefraction or drug.
2. Manifest hyperopia: This type of hyperopia is not hiding but it is noticeable. Therefore, it is that part of total hyperopia that cannot be compensated for by the ciliary tonus. In the subjective refraction it represents the amount of spherical plus power that would completely relax the patient’s accommodation while viewing distant targets. It is therefore the manifest errors that are being corrected (or compensated for) when such lenses are prescribed.
3. Absolute hyperopia: This is that portion of the total amounting of hyperopia, which cannot compensated by the accommodative system. It could be regard as a situation where the basic amount of hyperopia present in a given eye is greater than the amplitude of accommodation, which means without doubt, this cannot be corrected by accommodation.
4. Pathological hyperopia: This is caused by abnormal ocular anatomy. It means the shape of the eye is not within the bounds of normal variance. This type of hyperopia is typically caused by injury in the eye and abnormal development of the eye etc. pathological hyperopia condition is more likely to require treatment in addition to the use of corrective lenses, but depending on the exact cause of the condition, further medical treatment or surgery may be required to correct the condition and preserve the health of the eye.

 Classification based on degree of error

Hyperopia could be classified according to the degree of the error, listed below:

1. Low: This is hyperopia of less than +3.00 dioptres (+3.00D). hyperopes in this category could manage with visual tasks (for distance or near) without glasses until they approach the early presbyopic years (35 years and above)
2. Medium: This represent hyperopia of between +3.00 and + 5.000. This group of hyperopes may not be able to perform normal visual task conveniently without lenses even in their youthful year (less than 25 years), and the situation is expected to become worse when such persons are over 25 years of age.
3. High: This includes hyperopia of more than +5.00 dioptres (+5.00D). individuals in this category would be unable to perform normal visual tasks without their spectacles even in their youthful age.

 Symptoms of hyperopia

If you are long-sighted (hyperopia) you can see distant objects clearly, but objects near to you are out of focus. Symptoms of hyperopia is divided in two categories;

1. Adults: The eye sight of adults often deteriorates with age. Long-sightedness in adults (presbyopia) often becomes more noticeable after the age of 40. If you develop long – sightedness, you may notice that

• Nearby objects are fuzzy and out of focus but distant objects are clear.
• You have to squint to see clearly.
• Your eyes may feel tired after activities that involve focusing on nearby objects such as reading, writing or working on a computer.
• You experience pains or burning in your eyes.
• You experience headaches.

2. Children: Children who are long sighted do not often have problems with the eye their eyes sight, the lenses in children’s eyes tend to be more flexible than those of adult and are able to compensate for long sightedness. However, it is still important that young children have regular eye sight tests to check for conditions such as long sightedness. If left untreated, long sightedness can lead to complications such as crossed eye (strabismus) or lazy eye (amblyopia). If your child is severely long sighted, the signs and symptoms may include
3. Red or tearful eyes
4. Squinting when looking at close objects
5. Blinking and rubbing their eyes more than usual
6. Reading problems
7. Headaches

 Diagnosis long-sightedness

Refractive errors such as long sightedness are usually identified during early eye test.

Eye test

Eye test are carried out by an optometrist and usually 20 to 30 minutes. During the test, your vision and the health of your eyes will be checked. An eye test will usually include:

1. History and symptoms: the optometrist will start by asking whether you have any specific problems with your sight and how long it has been going on. They may also ask about your general level of health, including any medication you take and your lifestyle
2. Eye examination: An optometrist will check that your eyes are healthy and that you do not have any underlying medical problems. They will examine the inside of your eye using an ophthalmoscope, which is a torch that shines light through your pupil. This also tests your pupil reflexes (whether your pupils shrink in response to light) your eye movement and co- ordination will also be checked to make sure both of your eyes are working together. Other tests may also be carried out, depending on your age and medical history. Eye condition that your optometrist will be looking for include;

• Glaucoma: Pressure changes in the eye that can damage the optic nerve.
• Diabetes retinopathy: where high blood pressure and high blood sugar cause new blood vessels to form in the eye, which can obscure your vision.

3. Vision test: if you wear glasses or contact lenses, your vision will usually be tested both with and without them (so remember to take them with you). The optometrist will usually assess your distant vision, your near vision (for reading and close work) and your intermediate vision (for using a computer). A simple visual acuity test will help the optometrist assess how good your vision is. You may be asked to read from a Snellen Chart, which is a series of letters, that becomes progressively smaller on each line. Your optometrist will then carry out further tests to determine the extent of your problem and the exact type of corrective lenses that you need.

 Treatment of hyperopia

There are three ways of correcting hyperopia, which are; prescription glasses, contact lenses and laser surgery in some cases.

1. Prescription glasses: Long – sightedness or hyperopia can usually be corrected with glasses made to your prescription. Convex lenses (thinner at the edge than at the centre) are used to correct long – sight. The curvature of the lens, its thickness and weight will depend on how severe your long –sightedness is. By wearing a lens made to your prescription, light rays will fall onto your retina, allow you to focus accurately. The lens of the eye becomes stiffer with age, so the strength of the prescription may need to be increased as you get older as been said by optometrists that at least two years, our glasses must be renewed. It is possible to be both long-sighted and short- sighted, if this is the case you may need to wear two different pairs of glasses, alternatively, you could wear varifocal or bifocal lenses, which allow you to clearly see objects that are both near and far.

2. Contact lenses: Contact lenses can also be used to correct long-sightedness in the same way as glasses. Some people prefer contact lenses to glasses because they are light weight and virtually invisible. Contact lenses are available in many different materials and designs, some lenses can be worn for a day and discard (daily disposable). Others can be disinfected and re-used or worn for longer periods and kept in overnight.

Your optometrist can advise about the most suitable lens for you. If you wear contact lenses, it’s important that you maintain good lens hygiene to prevent eye infections developing.

3. Surgical treatment: There are various surgical techniques to treat long-sightedness. The most reliable uses are laser surgery. Surgical treatment for long- sightedness involves increasing the curvature of the cornea to improve its focusing power by removing some tissue from the edge of the cornea. The benefit of laser surgery compared with traditional surgery is that instruments do not have to enter the eye, which means that the risk of damage or infection is lower. There are three main types of laser surgery which are;
4. Laser in situ keratectomy (LASIK)
5. Photorefractive keratectomy (PRK)
6. Laser epithelial keratomileusis (LASEK)

Conclusion

In conclusion, hyperopia is a refractive error in which rays of light are brought to a focus some distance behind the retina which lead to blurred vision while viewing a near object. In children, severe long-sightedness can cause them to ‘over –focus’ and experience double vision. This can lead to one eye turning away resulting in a strabismus or amblyopia (lazy eye) therefore, it’s important for young children to have regular eye tests so that any problems are detected early. Regular eye tests is very essential as part of the routine screening programme.

References

American Optometric Association (2014).Optometric Clinical Practice Guideline Care Of The Patient With Hyperopia. Washington.

Bannon, R.E and Walsh, R.  (2010). Hyperopia  Am. J.  Optom 22:1010–11.

Chou, B. (2006). Refractive Error and presbyopia. Retrieve from http://www.refractivesource.com on 10^th April, 2016.

Money, J. (2015).Condition of the eye (hyperopia). Visual Optics (Unpublished)

Odjimogho, E.S. (2004). Understand common eye problems (published).