Myopia, or nearsightedness, is a very common spectacle error. It is the second most common cause of poor vision worldwide, and the incidence is increasing rapidly. It is estimated that by 2050 between 50% and 60% of people will have to wear spectacles to correct for myopia. Myopia is also associated with a high risk of other eye problems that can also be vision threatening. These include glaucoma, cataract, retinal detachment and macular disease.
In myopia the light entering the eye is focused in front of the retina, because the eye is too long. The result is that myopes can read without spectacles but need spectacles to see well in the distance. The risk of progressive myopia is also increasing worldwide. With progressive myopia the spectacle error increases dramatically in children due to the progressive elongation of the eyes. Just as the child’s body grows, the eyes also grow and in some children this growth is progressive and excessive leading to severe myopia. These progressive changes can however be prevented with the appropriate treatment.
CAUSES OF MYOPIA
Both genetic and environmental factors contribute to the development and progression of myopia.
A family history of myopia increases the risk of developing myopia. The risk of developing myopia is increased if close family members, as well as parents, have myopia.
In order to focus at close, the lens inside the eye changes shape. This change in shape is necessary to focus the incoming light sharply on the retina, and it is called accommodation. At the same time the eyes rotate inwards, or converge, to allow both eyes to focus at a closer distance. In some children these two processes do not synchronize well, putting more strain on the eyes to focus at near.
Spending more time indoors and doing near work is a stimulus for the eye length to increase, and therefore myopia will develop and progressively increase.
TREATMENT OF MYOPIA
The treatment of myopia is aimed at not only avoiding the development of myopia, but also retarding the progression. Children can be treated from the age of six years, and the effect can be maintained up to the maturation of vision at around 14 years of age.
Spending more time outdoors and less time indoors with close work is effective in avoiding the development of myopia. Studies have also suggested that cold-white LED lighting contributes to the progression of myopia.
Specialized glasses and contact lenses help to relax the accommodative effort for near work, and this in turn reduces the progression of myopia.
Medication that relaxes the muscles involved in accommodation has been shown to be very effective to prevent the progression of myopia. This medication needs to be prescribed by an ophthalmologist.
A combination of the above treatment plans is usually necessary to provide success in the prevention of progressive myopia and patients’ developing severe myopia that predisposes to other eye problems. The routine measuring of the length of the eye is very important in the evaluation of the success of the treatment.