Smartphone use and the risk of myopia in adolescents

Myopia is a refractive error caused by elongation of the eyeball. In
particular, high myopia is associated with a significant risk of severe visual
impairment. Previous work from our research group showed that 1 in 3 highly
myopic persons will develop severe visual impairment during his/her life. The
prevalence of myopia is rising all over the world; youngsters are now more
often myopic than previous generations. As the whole curve of refractive error
is shifting towards myopia, the number of persons with high myopia is
increasing as well, and therefore the number persons at risk of visual
impairment. An established risk factor for myopia is education, and it is
becoming more and more clear that increased near work and decreased outdoor
exposure are important lifestyle factors. Increased use of handheld digital
screens has been postulated as a causal factor, but the results of current
studies based on questionnaires have been inconsistent. The most commonly used
digital device among children and teenagers nowadays is the smartphone.

The primary objective of this study is to investigate the association between
smartphone use and risk of myopia in teenagers.

This study is designed as an observational study in secondary school children.
Three schools will be invited to participate. Children in the first, second and
third grade, aged 12 to 16 years will be asked to participate in the study. All
participants and their parents/guardian will be informed prior to the study and
should give written consent. After consent, an online questionnaire will be
obtained with items related to near work activities, outdoor exposure, parental
myopia and socio-economic status. The participants will then be asked to
download a mobile application on their smartphones. This application will run
on their mobile device for a maximum of 5 weeks, without any required actions
from the participant. The mobile application records smartphone use, distance
between face and screen, illuminance and screen brightness. After 5 weeks the
mobile application automatically stops and transfers the obtained data to a
secured server. Furthermore, outdoor exposure is measured electronically by
means of a light sensor data logger on their clothing for 7 days. After 7 days,
the logger will be returned to the researcher and data can be transferred from
the logger via USB to a computer in the Erasmus MC. Standard eye measurements
will be performed at school. First, the visual acuity will be measured to
identify children that need to be referred to an ophthalmologist or
optometrist. Measuring visual acuity alone is not sufficient enough to
distinguish between myopia, hyperopia and astigmatism (12), therefore
refractive error will be measured by means of cycloplegic autorefraction.
Cycloplegic eye drops (cyclopentolate eye-drops) will be used to dilate the
pupil and inhibit accommodation. After 30-40 minutes set in time for the
cyclopentolate 1%, measurement of the cycloplegic refraction and ocular
biometry will take place within 5 minutes. Cycloplegic refraction will be
measured by means of a Retinomax and ocular biometry by means of an IOL
(Intra-Ocular Lens) master.

This study is an observational study with clinical measurements that are
standard in optometric practices. Pupil dilation with cyclopentolate eye-drops
are a potential burden but are obligatory to obtain accurate refractive error
measurements. Side effects of these drops include temporary photophobia and
reduced accommodative power for the rest of the day, which we will address by
providing reading glasses.