In order to see well, whether from far or near, our eye must be able to focus light rays from the outside world on the retina. The eye that sees correctly is said to be "emmetrope".
In the emmetrope eye, light rays are focused on the retina by the cornea and the lens, creating a sharp image that is transmitted to the brain. The crystalline lens is elastic, especially in young people, and during the accommodation process the ciliary muscles adjust the shape of the lens to focus images correctly. When, on the other hand, the focusing of images on the retina does not take place correctly we are in the presence of a refractive defect o ametropia.
Refractive errors lead to blurred and unclear vision.
The Refractive errors most commonly found in the paediatric population are:
-Miopia: light rays are focused in front of the retina resulting in blurred vision; in particular, near objects appear clear, while distant objects appear blurred;
-Hypermetropialight rays are focused behind the retina, so that mainly near vision is blurred and reading is therefore difficult;
-Astigmatism: distorts or blurs the vision of both near and distant objects. This refractive defect is due to an abnormal curvature of the cornea, which instead of being spherical has an oblong or oval shape: it looks like a basketball rather than a football.
La vision is a fundamental condition for the development of children and for their correct interaction with their surroundings. In particular, it is of paramount importance to check the vision of pre-school children: in fact, their visual system is still developing and the undetected refractive errors can cause amblyopia (lazy eye). This condition is characterised by poor visual acuity in one eye compared to the other and often develops during early childhood. Although amblyopia can be treated at any age, it is clear that early diagnosis and timely treatment lead to better results. On the other hand, amblyopia secondary to uncorrected refractive errors in childhood leads, in adulthood, not only to visual problems but also to social, educational and economic problems. Reduced vision, loss of stereo-acuity and loss of contrast sensitivity in fact limit performance and professional abilities, resulting in reduced quality of life and a negative psychosocial impact.
Symptoms
There are behaviour that parents, teachers and health professionals may notice in a paediatric subject who has visual difficulties.
The child:
-needs to bring objects close to the eyes to see them;
-moves awkwardly;
-does not notice things happening in the distance.
These are typical behaviours that could signal the need for an eye check-up. Given the importance of specialist check-ups in paediatric age, the World Health Organisation (WHO) recommends and supports school screening programmes to prevent sight loss due to refractive errors in childhood. In this regard, teachers play a primary role in screening programmes, while awareness campaigns and parental education help overcome cultural barriers against visual rehabilitation.
Treatment
The correction of refractive errors involves the use of lenses in the form of temples or contact lenses, and in special cases the use of refractive surgery. Â
The choice of method depends on the age of the child, the type of error and the needs of the patient. Options should be evaluated in cooperation with the parents, although glasses are usually the preferred option.
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Sources:
-Child Development and Refractive Errors in Preschool Children. Josephine O. Ibironke et al. Optom Vis Sci, 2011 February.
-Future Problems of Uncorrected Refractive Errors in Children. Emine Kilic-Toprak. Procedia - Social and Behavioral Sciences, 2014.
Dr. Carmelo Chines
Direttore responsabile