What is hyperopia and its causes?
If you see blurry up close, and you are too young to have tired eyes, see your ophthalmologist, as it could be hyperopia, an eye defect that can be corrected with glasses, contact lenses, or surgery.
Hyperopia is an eye defect in that light rays, rather than impact exactly on the retina, are concentrated at a point located behind the same. Its main reason is the cornea’s scarce curvature or because of an eye size somewhat smaller than normal size. It translates into difficulty in seeing up close, with far vision being better.
It is the most frequent ametropia or refractive error. At birth, 70% of children have hyperopia called physiological hyperopia, but the babies’ lens is very elastic, which helps them compensate for this problem through accommodation. Accommodation is the filiary muscles’ ability, which is found inside the eye attached to the lens, to modify its geometry.
Hyperopia should be corrected spontaneously in adolescence since as the eye develops and grows in size, the defect diminishes. If this does not occur, the defect will last over time, and that is when the symptoms begin to be observed.
We can distinguish two fundamental types of hyperopia: one that is not manifested by compensation through accommodation of the ciliary muscles ( latent hyperopia ), and one that produces symptoms, since it is not compensated, requires an accommodative effort, causing a decrease in visual acuity ( manifest hyperopia ).
Causes of hyperopia
The reasons why this disorder can develop and that are considered causes of hyperopia are:
- Ocular diameter too small: it is called axial hyperopia, and it would correspond to physiological hyperopia in children due to small eye size, but as the globe develops, it grows and disappears. To get a rough idea of the defect, each millimeter of shortening of the eyeball axis is about three diopters. In microphthalmia cases (a genetic defect with excessively small eyes), 20 diopters can be reached.
- The reduced optical power of the cornea or lens: there is a decrease in the convergence power of the lens, being more frequent in adults, associated in many cases with diabetes. It is known as index hyperopia.
- Trauma or corneal diseases: this supposes a flattening of the cornea, which leads to the alteration of refraction focusing behind the retina. It is called curvature hyperopia.
- Absence of the lens: as in the cases called aphakia, which are congenital disorders, or in cases where there is a subluxation of the lens, which implies a loss of its normal position.
Symptoms of hyperopia
The clinical manifestations associated with hyperopia will largely depend on the degree of involvement that occurs. In this way, and as described in the cases of physiological hyperopia in children, the symptoms go unnoticed; the children do not seem to have any visual defects due to the accommodation power provided by their ciliary muscles.
The symptom of hyperopia that those affected mainly notice is that their near vision is blurred. They can also manifest other symptoms due to the effort that the eye must make to try to compensate for the defect, such as:
- Visual fatigue.
- Eye pain.
- Sometimes the distant vision is also blurry.
- Children can also have strabismus and amblyopia. It results from accommodative overexertion, developing a greater understanding of the undivided eye, and causing a lazy eye (amblyopia) in the deviated eye.
- Itchy eyes
- It is also common to observe the redness of the eyes.
- Some young people have a predisposition to developing styes and inflammation of the eyelids frequently.
In older people, hyperopia should not be confused with presbyopia, also known as eyestrain. It is in adults with very high and long-standing hyperopia. There may be a greater risk of glaucoma due to having a small eye, flattening of the cornea, and a shallow anterior ocular chamber. This increases eye pressure and glaucoma symptoms.