The early detection of visual defects in childhood is essential in order to have a lifelong optimum vision quality, tells us Dr Juan García de Oteyza, devoted to ophthalmology for four decades now. Which are the most common visual problems in childhood? In childhood, the refractive defects are the most frequent ones: hypermetropia, myopia and astigmatism. Also strabismus, in which early detection is essential to avoid amblyopia, popularly known as lazy eye, and that is a direct consequence of strabismus. In these cases, it is especially important not to delay the appointment with the ophthalmologist as there is a direct relationship between early detection and therapeutic success chances: parents must know that the consequence of not treating a lazy eye before the age of 7 is irreversibility for the rest of the child’s life. You referred to the importance of early detection… How can we know if a child sees properly? There are alert signals like the fact that the child gets very close to the T.V., that he turns his head sideward when focusing, or that he has relationship problems with his outer world. Many years ago, I developed a test, available to all parents, in order to make the detection of visual defects in children easy because, often, if they aren’t very important or don’t affect vision seriously, they allow leading a normal life with an average vision and they may go unnoticed. From the prophylaxis point of view, a first control test at the ophthalmologist’s is advisable at the age of 3-4, unless you detect an anomaly before. If parents have a refraction defect the early detection is important because they are very often hereditary and, the sooner they take their child to the ophthalmologist’s and the correction glasses are applied, the better, for it’ll be easier to be solved. One must also learn to see properly… “The constant use of mobile phones, tablets and videogames causes eyestrain along with irritation, lachrymation and often blurred vision too.”    Therefore, one must avoid learning to see badly… Indeed, because if the information that gets to the retina form the outer world isn’t sharp enough, the brain gets a wrong signal and “gets used” to seeing badly. If that goes on for years and the appropriate conditions aren’t created so that the brain sees correctly, your vision will be deficient for the rest of your life. Binocular vision, as well as visual acuity, are learnt as the years go by. This learning process culminates by the age of 7. This means that, if at that age our brain hasn’t learnt to see properly yet, it is highly unlikely that these deficiencies will be corrected afterwards. How does the constant use of screen devices affect a child’s vision? The constant use of mobile phones, tablets and videogames causes eyestrain along with irritation, lachrymation and often blurred vision too. It all is mainly due to eye dryness caused by not blinking. Moreover, in children with a not corrected visual defect these symptoms may worsen even leading to headaches after playing with the device for a short while. Therefore, my general advise is dosing their use by parents to avoid this sort of problems.