February 2, 2022 Author : Paulo Silva Guerra What is myopia and what are its symptoms? Myopia is a vision disorder – a refractive error. People with myopia have difficulty seeing distant clearly . In myopia, light rays coming from a distant object that penetrating the relaxed eyeball are not focused directly on the retina, as would be normal (emmetropia), but on a focal point anterior to the retina. This may be associated with: An eyeball with and anteroposterior axis longer than normal, what is called axial myopia; A more pronounced curvature of the eye refractive structures – the cornea and lens, what is called refractive or curvature myopia. Many cases of myopia result from a combination of both factors . Focusing on a point anterior to the retina, like happens in myopia, is translated into a blurred image from afar and sharp for the closest objects. The greater the myopia, the greater the need to bring objects closer to the eyes to have a clear vision. The most obvious symptoms of myopia are: Difficulty in identifying objects in the distance; Difficulty driving; Difficulty watching the blackboard at school or television at home; Need to squint to see clearly in the distance and tendency to bring objects closer to get a better view. Why does myopia develop? At birth, hyperopia, or near vision difficulty, averages +3D, by the end of the first year of life it is +1D, and by age 6 children are usually emmetrope, i.e., their eyes have a normal refractive power. When myopia develops, this is usually between 7-16 years of age and is related to an increase in the axial length of the eyeball. It worsens by about 0.5D per year until around 18-20 years, at which age tends to stabilize in most cases. Myopia is a multifactorial condition , that is, it is due to several factors. Different forms of myopia are influenced in varying degrees by genetic and environmental factors. Genetic factors Children of parents with myopia have an increased risk of developing myopia, which is related to the presence and expression of certain genes responsible for myopia. Some of them are already identified on chromosome 18. Environmental factors It has been shown that periods of prolonged visual effort for near distances (and not so much for intermediate distances) are associated with the development and progression of myopia. This explains the reason why studies carried out in populations with a high level of education, which have professional activities that require spending more time seeing close, show a much higher prevalence of myopia than in other populations that are not subject to this type of effort. There are even eastern population groups (Taiwan) with a much severe myopia at all ages, reaching 84% in the 16-18 age group. Another important environmental factor is outdoor activity . Fewer periods of outdoor activity have been shown to be associated with a higher frequency of myopia. Age and initial refractive error are two other important factors for the worsening of myopia. The younger the child/adolescent and the greater the refractive error at the time of myopia diagnosis, the greater the risk of myopia progression. Treatment of myopia Myopia can be corrected using: Glasses; Contact lenses; Refractive surgery. All these treatment options are valid and effective , they allow the correction of the refractive error caused by myopia, but: Do not cure myopia; Do not prevent the progression of myopia: Do not modify the structural changes of the eyeball associated with myopia. Glasses and contact lenses Glasses are the ideal solution to correct myopia and also the safest for children up to 16 years of age . From this age and the greater the myopia, the thicker eyeglass lenses become heavy, uncomfortable, deform the image in the periphery and alter the facial aesthetics. That is why contact lenses or refractive surgery are common. Refractive surgery Refractive surgery may be indicated in people with myopia over 21 years of age and with myopia stabilized for at least 12 months. Most people with myopia can correct it by refractive surgery, but it is essential to carry out a set of non-invasive eye exams before, to determine the eligibility and the appropriate technique for the surgery. The correction of myopia by refractive surgery can be done in two most frequent ways: LASIK , acronym for laser-assisted in situ keratomileusis, which is the most common surgery; Phakic intraocular lens (IOL) implantation . LASIK When performed with a laser (femtoLASIK or photorefractive keratectomy - PRK), it shapes and regularizes the corneal surface, correcting myopia and the astigmatism possible associated. It is considered a safe procedure ; It is performed under local anesthesia, takes 15-20 minutes and does not require hospitalization; LASIK does not cause postoperative pain and allows vision to be recovered in less than 24 hours ; Usually both eyes are operated in the same intervention ; The level of satisfaction with the intervention and its results is very high . Intraocular lens (IOL) When it is not possible to correct myopia with a laser, which usually happens with myopia greater than 6D or when the cornea is thin, there are solutions, such as the placement of a phakic IOL, which allow the correction of higher degree myopia. It is also considered a safe procedure ; It is performed under general anesthesia , but does not require hospitalization; Does not cause postoperative pain ; The level of satisfaction with the intervention and its results is high . Refractive lens extraction In people over 50 years of age and with high degree myopia , another technique for surgical correction can be considered, which is called refractive lens extraction. It is a surgery similar to the cataract one , in which the lens is removed, and a definitive intraocular lens is placed that allows the correction of the refractive error, be it myopia, hyperopia and/or astigmatism. Frequently asked questions about myopia Maintaining regular eye surveillance , starting in childhood, is critical to early identification and correction of refractive vision errors. Meet the ophthalmology clinical team from Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
