Hyperopia or hypermetropia “farsightedness” is a refractive error which affects many people. The understanding of hyperopia is quite complicated. The term “farsightedness” plays a role that makes people misunderstand what hyperopia really is?
Hyperopia is wrongly called “farsightedness.” I met patients who think that they can see far things better than normal people do, because they have ”farsightedness,” and put a red line under the word “far”.
Farsightedness as a term has no much things to do with the real meaning of the condition “hyperopia.” Hyperopia affects far and near vision of the person. It is true that it affects near vision more than far vision. Also, in its lower degrees, its effect on far vision is not that obvious, but symptoms are that obvious at far and near. Hypermetropia or “hyperopia” is different from “presbyopia.” Presbyopia is the refractive error that solely affects near vision with age and could easily be corrected with a multifocal contact lens.
Hyperopia “Farsightedness” Meaning & Definition
Let us put terms away in our explanation of hyperopia. We don’t want to define hyperopia linguistically here. So, we will not get stuck with terms which may be wrong or, at least, suggest wrong understanding. Let us understand hyperopia “farsightedness” as it is really is before anyone calls it hyperopia or “farsightedness.”
Scientists found that some people eyes do not focus images as normal eyes do. The light rays of images in these people don’t bring to concentrate in the retina (where they are supposed to). They reach the retina before they are focused. Or in other words, if their extension is drawn, they will focus on the retina as you see in the image below.
Hyperopia “Farsightedness” Causes
In hyperopia, the images reach the retina before they are focused for two causes:
- The length of the eye is shorter than normal, and that’s why the light rays of the images reach the retina before they are focused. If the eye has the normal length, these light rays focus will be located in the retina.
- The eye has less ability to bend light ray’s “refraction” than the normal eyes. So, the eye is not able to focus light rays in the appropriate location “the retina” because its refractive power is lower than the “required power.”
Until now, the above words are extremely true and right but not for all circumstances. And here it comes the point. Here it comes the secret key in the understanding of hyperopia.
The above words are correct when the light rays entering the eye are parallel and not diverged — all light rays coming from 6 meters distance or further entering the eye as parallel light rays. All parallel light rays need the same refractive power “eye’s ability to bend light rays” to be focused in the same location in the eye.
When light rays enter the eye from any distance less than 6 meters, the equation changes here. Light rays entering the eye (from less than 6 meters) diverge and not parallel. These light rays need different refractive powers to be focused in the same location in the eye.
Light rays coming from 4 meters distance reach the eye more diverged than light rays coming from 5 meters. Thus, the light rays coming from 4 meters distance need more refractive power than those coming from 5 meters to be focused in the same location in the eye. Also, light rays coming from 3 meters need more refractive power than that needed for light rays coming from 4 meters to be focused in the same location in the eye. The shorter the distance light rays entering the eye (for any distance less than 6 meters), the more refractive power is needed by the eye to focus them in the same location.
For this mission (focusing diverge light rays), Our eyes have a unique ability that enables it to increase its power. This ability occurs by changing the eye lens shape and is called “accommodation.”
Normal Refractive Power
Originally, this mission is required by normal people. The eye has the same normal refractive power to focus all parallel light rays, coming from 6 meters or further, on the retina. For any diverge light rays (coming from less than 6 meters), the eye use “accommodation” to increase its power by the appropriate amount to focus these light rays in the retina.
In very short words, now we know that all people eyes can increase its refractive power “accommodation.“ But as we knew earlier, the eye in hyperopia has less refractive power than normal. So, the secret key is that the eye in hyperopia takes advantage of “accommodation” to compensate for its less power in hypermetropia.
If the eye doesn’t use accommodation, parallel light rays coming from 6 meters or further reaches the retina before they are focused. But in fact, the eye uses accommodation and increases its power to make these light rays focus in the retina. If light rays are coming to diverge (from less than 6M), the eye exerts more accommodation for any nearer distance to focus these light rays in the retina.
So, what’s the problem then? The eye is using its accommodation to correct hyperopia.
That’s true.
But accommodation has limits. So, it can’t correct all degrees of hyperopia.
Also, different distances need different powers. Nearer distances need more powers, and that’s why hyperopia is famous to be the problem of near.
With all that, accommodation is exhausted with time. As we know, accommodation’s basic function is near work in normal people. Using it for functions other than what is normally made for leads to “symptoms.”
Hyperopia “Farsightedness” Symptoms
When the eye uses accommodation for distance tasks in hyperopia, accommodation is exhausted with time and this cause eye strain and headaches.
Accommodation is capable of correcting low degrees of hyperopia and makes the vision clear at a distance. However, it can’t alter higher degrees of hyperopia, and blurred distance vision is occurring.
Near vision tasks require more refractive power and the eye in hyperopia has less refractive power than normal. This makes hyperopia causes more problems in close tasks. Near vision is blurred constantly or after few periods of near work in hyperopia. Also, eye strain and headaches are more evident in near tasks because the doubled role required by accommodation.
Also, age is an important factor in the symptoms of hyperopia because the amplitude of accommodation decreases with age. Younger persons have more amplitude of accommodation and thus can compensate higher degrees of accommodation with fewer symptoms. Also, lower degrees of hyperopia may present in young persons with no symptoms.
However, older persons have a lower amplitude of accommodation, and thus can’t compensate for hyperopia as younger people do. Low degrees of hyperopia may present with no symptoms until the person reaches 30 years age or older.
So, how hyperopia is treated?
Hyperopia “Farsightedness” Treatment
- Eyeglasses: your eye doctor will prescribe eyeglasses. The prescription contains a number of the power of the lens that will correct your hyperopia. This lens power will increase your eye’s refractive power to focus images on the retina.
- Contact lenses: with the same idea of spectacle’s lenses, contact lenses rest on your cornea and correct your hyperopia. Contact lenses have some advantages over glasses which are:
- Cosmetic appearance: as some people don’t like how they look when wearing glasses and colored ones can even enhance your looks.
- Optical advantages: the quality of images reach the eye is better in contact lenses than in glasses especially in high hyperopia (over 6 Diopters hyperopia). Also, contact lenses are a better choice when there is a considerable difference between the amount of hyperopia in each eye.
- Refractive Surgery: this treatment alternative gives you the freedom to have clear corrected vision without wearing glasses or contact lenses. The most commonly used procedures nowadays are:
- PRK: in this procedure, the surgeon reshapes your cornea by applying laser directly on it. This increases the power of the cornea and makes the eye able to focus images on the retina.
- Lasik: In this procedure, the surgeon makes a flap in the outer cornea. He then applies laser pulses to the intermediate corneal tissues to correct the hyperopia.
- ICL (Implantable Collamer Lens): This is a new procedure invented to correct refractive errors. An intraocular lens is implanted in the eye that corrects your hyperopia.
