Hyperopia

Hyperopia is a refractive defect characterised by the focusing of images on a plane behind the retina. The result is that the image of objects closer to the eye is blurred.

In these cases the axial length of the eye is small or the cornea/crystal combination is unable to converge the light rays on the retina. However, distant objects remain in focus and patients with this defect, when younger, see very well in the distance without any correction. Hence the name hypermetropia (seeing well in the distance). With age and the consequent loss of the ability to accommodate, the first symptoms manifest themselves.

The prevalence of hyperopia is high in children although the vast majority become emmetropic (someone who can see well at any distance without any correction) by the age of 10 to 15 years due to growth and consequent increase in axial length.

It increases, however, with age, due to loss of accommodation of the lens.

A young person until adolescence has a high accommodation capacity (the ability of the lens to focus). Therefore in children and adolescents it sometimes goes unnoticed. They easily compensate (focus) 2 or 3 dioptres (we speak of dioptres as a unit of measurement of the degree of refractive defect). A child can focus up to about 16 diopters. Hyperopia can therefore not be detected, especially if the dioptric value is not very high. They can therefore read very close to the eyes.

Higher values above 4 dioptres may already give some symptoms, especially in close vision or reading.

The symptoms are usually headache or feeling unwell, red eyes and itching after prolonged reading. When reading, the eyes need to focus on 3 diopters corresponding to the near distance. If we add the 4 or 5 diopters of hyperopia we can imagine the eye strain of keeping the focus for a long time. Young adults show the first symptoms, initially in reading and later also in distance.

In some children with high hyperopia of 5 diopters or more, the first sign may be the appearance of a strabismus. The child twists one eye when focusing close. Since accommodation (focusing close) is directly linked to convergence (when we focus close our eyes converge in order to maintain binocularity), the excess of accommodation, necessary to focus on those 7 or more diopters, causes an excess of convergence with the appearance of accommodation strabismus.

Once again we draw attention to the need for early observation of pre-school children, especially in cases where there is a family history.

The symptomatology and the objective examination performed by the doctor when doing the refraction are the essential steps in the diagnosis.

The correction will be done with glasses or contact lenses. Also the simple use of corrective glasses easily resolves the aforementioned issue of accommodative strabismus.

In adults, refractive surgery is almost always possible. The correction of hyperopia by LASIK (with excimer laser) presents some difficulties due to the anatomical particularities of the hyperopic eye. The cornea is generally flatter, which predisposes it to regression. The stabilisation of refraction is also delayed because the hyperopia will become increasingly manifest with the loss of accommodation relative to age (latent hyperopia).

The previous study of these patients must always include an examination, the cycloplegia. In this examination, drops are placed in the eye with a medicine that temporarily paralyses the accommodation of the lens. This allows the entire hyperopia of the eye to be assessed as there is no interference with accommodation. The difference between the dioptric values found before and after the examination gives the latent hyperopia. If the value is very high, we will know that the patient will become more hyperoptic over time.

Surgery must be a compromise between the dioptric value existing at the time of the operation and the one that we think, based on observation, the patient will bear. For these reasons, surgery should be carried out as late as possible, as the risk of reoccurrence is reasonable.

Phakic lens surgery is not always possible because the depth of the anterior chamber is usually insufficient, as they are small eyes (shorter than normal axial length).

Hyperopic patients who do not want to wear glasses are generally advised, once presbyopia, or tired eyesight, has set in, to have the lens replaced with a multifocal lens, thus resolving their vision at all distances.