By Alice Targon, optometrist and student of SAERA.
Uncorrected refractive errors are the commonest cause of visual loss (1); it is very important to detect them at a young age.
The World Health Organization estimates that 13 million children aged 6-15 years worldwide are visually impaired from uncorrected refractive error (2).
There are three refractive errors: myopia, hypermetropia and astigmatism.
Myopia (or short-sightedness) is the commonest visual disorder with increasing prevalence among developed country around the world. (3)
This ametropia affects currently a large portion of the world population and typically develops in children from 6 to 10 years, period also known as “the school years”, progressing in severity throughout adolescence. In fact, the signs of this disorder appear more clearly when the child in the classroom is not able to see the blackboard. School-based vision screening may be an effective mean of detecting affected children and improving their visual function.
But what is myopia?
It is due to eye’s refractive power being too strong or to the eyeball being too long. In both conditions, light rays that enter the pupil are focused in front of the retina giving a confused image.(3)
Treatment of myopia at an early stage is of paramount importance, as shortsightedness poses a significant risk for several ocular disorders which could result in blindness (glaucoma, retinal detachment, etc…).(4)
Correcting refractive errors such us myopia requires the following steps: measuring visual acuity in each eye without any form of correction, followed by measurement of the type and degree of refractive errors in each eye, which can be done clinically or using an automated refractometer. After the objective tests, since we are talking about school–age children, we can assume the possibility of performing a subjective test. The final step is to dispense a visual correction.
There are multiples types of visual correction for both children and adults.
Spectacles are the most used type of ocular correction. According to current data spectacle wear is higher in children with more severe refractive errors and usually in girls. Despite spectacle correction improving visual function, children do not wear spectacles for a variety of reasons, such as no benefit perceived , loss or breakage, misconceptions that spectacles will make their vision worse, being tested, etc. (5)
Another method to correct vision is using contact lenses. Recent studies have shown children to be successful in wearing contact lens in different modalities.
An important practical difference between this type of correction and the one with spectacles is the fact that contact lens correction does not modify how the person looks; doesn’t have an impact on social interaction. Contact lens correction is also more comfortable when playing sports.
It is also known that the use of some type of contact lenses can slow down the progression of myopia in children, but, currently no universal guide lines have been established. (4)
On the other side, contact lens wear requires care about the procedures, in order to maintain the health of the ocular surface.
With increasing numbers of children wearing contact lenses, information about how often they can be expected to wear their lenses in comparison to spectacles may help practitioners to understand that contact lens wear provides continuous correction trough the day but the lenses may not be worn that often.
Determining whether contact lenses and spectacles wearing times differ and assessing whether the amount of time that children wear their contact lenses encompass the most part of the day are very usefull to learn about how the contact lenses are used by young myopias and may help prescribing their correction.
This is the aim of a study known as the “A.C.H.I.E.V.E. Study”, or The Adolescent and Child Health Initiative to Encourage Vision Empowerment (6), that was designed to investigate the effects of contact lenses wear on the self-perception of children who need to wear spectacles to correct myopia.
The subjects of the study were in the so called “scholar age” (8-11 years), had 10/10 with optical correction and healthy eyes, suitable for contact lens wear.
The objective of the analysis was to compare the amount of time subjects wore their assignment vision correction (spectacles or contact lenses) over the course of a week and to determine whether the wearing times between the spectacle and contact lenses groups differed.
As is always the case when looking at study results, it is necessary to remember that subjects in the study may act differently by virtue of study participation.
The data were obtained by using questionnaires and under the parents’ supervisions.
The results of this study lead us to reflect.
Subjects who were assigned to contact lenses did not solely on contact lenses for vision correction: they wore lenses less than the spectacles wearers wore their spectacles, but they wear vision correction slightly more than just spectacle wearers.
One might have expected more contact lens wear among subjects who participate in many sports, who were not satisfied with spectacles or who finds it difficult during activities.
According to this study none if this conjecture was true because it turns out those children wearing contact lenses reported higher levels of self-assessed athletic competence than those who wear spectacles.
Children may not feel the need to wear contact lenses all the time so that overall wearing time of contact lenses may not capture the necessity of lenses for selected activities.
They may wear contact lenses just when they feel it necessary for improved convenience, such us during sporting activities.
Another very interesting thing that comes out of this study is the results related to the “appearance scale”. The difference of wearing time between contact lenses and spectacles in children with a low score in the so-called appearance scale was about 4 hours. Therefore, it was not very significant.
Also, gender seems to play no role in determining wearing time. Since this study was taken in 2010, we take a look on the wearing time data of 2016; we can see that there still isn’t no statistically significant difference by sex for children aged 10–13 years is emerged. Otherwise, girls aged 6–9 years weremore likely than boys of the same age group to wear eyeglasses or contact lenses. (8)
According to the “A.C.H.I.E.V.E. Study”, we can afford to say that either spectacles or contact lenses yielded more meaningful total vision correction wearing time.
We can say that both are appropriate for 8 to 11 years old myopic children and can be offered as a primary vision correction option.
The aim of the optometrist must be to teach the correct instruction about how to use contact lenses to the children, such as how to put it on and off, for how many hours and of course how to clean them.
The optometrist also need to warn both parents and child about how to detect any signs of infection or malfunction due to lenses.
Children fitted with contact lenses should be also prescribed a pair of spectacles as back up.
Notes
This article is addressed to people who simply google the key words and optometrist who wanted to make an idea about this topic. I wanted it to be very simple and understandable by anyone.
Bibliography
Global magnitude of visual impairment caused by uncorrected refractive errors in 2004. Resnikoff, Pascolini, Mariotti & Pokharel.
School-based approaches to the correction of refractive error in children. Sharma A, Congdon N, Patel M, Gilbert C.
Basic English for opticians. Gentile, Scafati.
Interventions to control myopia progression in children: protocol for anoverview of systematic reviews and metaanalyses. Prousali, Mataftsi, Ziakas, Fontalis, Brazitikosand Haidich.
Spectacle wearing in children randomized o ready-made or custom spectacles, and potential cost savings to programmes: study protocol for a randomised controlledtrial. Morjaria, Murali, Evans and Gilbert.
A comparison of spectacle and contact lens wearing times inthe ACHIEVE study. Jones-Jordan,Chitkara,Coffey, Manny,Rah and Walline
To prescribe or not to prescribe? Guidelines for spectacle prescribing in infants and children. Leat
Percentage of Children Aged 6–17 Years Who Wear Glasses or Contact Lenses,by Sex and Age Group — National Health Interview Survey, 2016