farsightedness

Generality

Hypermetropia is a defect of spherical refraction in which the light rays coming from the infinite go into focus behind the retina, since the power of the ocular diopter is scarce compared to the length of the bulb.

It may happen that hypermetropia, especially if not elevated, remains undetected. In fact the hypermetropic patient, but also the emmetropic person (without sight defects), by modifying the shape of the crystalline lens, is able to increase the dioptric power and therefore manages to avoid hypermetropia. This mechanism involves a continuous use of what is called the reflection of accommodation, characterized precisely by the modification of the globularity of the lens based on the proximity or distance of the visual targets. The rays coming from an infinite distance are parallel and have the focus exactly on the retina (in an emmetropic subject). In this situation the crystalline lens is " accommodative rest " and takes on a more subtle, sharp and elongated shape. As the rays approach the eye, they become more and more divergent, so they would not focus on the retina but beyond it and the image would thus be out of focus. Here, in these cases, the crystalline element intervenes, increasing its curvature surface and thus assuming a more globular shape. In this way it increases its convergent power and allows the rays to fall equally on the retina.

With increasing age, accommodation is reduced physiologically and here is that hypermetropia becomes apparent, even for the forms that were previously unrecognized.

Symptoms

To learn more: Symptoms Hyperopia

In the child

In the child and in the young hypermetropia, visual acuity is good both for far and near but the continuous effort of accommodation gives rise to various disorders that are called accommodative asthenopia. It includes a sense of tiredness in the eyes, headache (headache) after reading, clouding of eyesight, eye burns, watery eyes and ease of developing conjunctivitis. Furthermore, the marked accommodative effort can cause a squint.

In adults

In the adult and in the elderly, on the other hand, there is a reduction in acuity that appears around the age of 40-50, when the accommodation can no longer compensate for the visual impairment and causes difficulties initially in near vision, simulating a presbyopia (problematic due to the reduction in accommodation due to advancing age), and then from a distance. Also here the headaches and the alterations of the conjunctiva are frequent.

Causes

The causes of hyperopia are:

• A diameter of the bulb shorter than normal ( axial hypermetropia ). It is certainly the most frequent cause.
• A curvature of the crystalline surface lower than the norm or its refractive index increased compared to the norm.
• An absence of the crystalline lens (rare), called aphakia.

Treatment

• Glasses with converging lenses (positive), which allow light rays to fall directly on the retina and not behind it
• Contact lenses with the same effect
• Laser surgery: it involves the removal of layers of the cornea to make its surface more curved.