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What is high myopia?

Myopia is a refractive error in which the images form behind the retina, which makes nearby objects appear clearly while those far away look very blurry.

We speak of high myopia when the degree of the refractive error is higher than six or eight dioptres and it occurs because of an excessive growth in the size of the eye. This increase in length does not only mean that we have to wear glasses with a high prescription in them, it also means that there's a risk of suffering from other potentially serious diseases.

The growth of the eye makes the retina become thinner and get weaker, thereby increasing the probabilty of having a haemorrhage, retinal lesions or even retinal detachment. Degeneration fo the vitreous body (gelatinous liquid that fills the eye) is also common, which leads to the appearance of floaters. In cases of very high myopia, the macula, the most important part of the retina, may gradually deteriorate, causing a progressive and irreversible reduction in visual acuity.

High myopia might also predispose a patient to glaucoma and early cataract development. 

Symptoms

The main symptomology of high myopia reduced visual acuity and the need to wear glasses to see clearly at a distance. Your glasses prescription will normally increase from childhood or adolescence until adulthood when it usually stabilises, however, in some case it slowly continues to increase over the years. 

Regular eye check-ups are recommended. Normal practice is to have a check-up annually. 

There is a series of symptoms that should raise our awareness of possible complications, especially, in the retina, the sudden appearance of floaters, seeing flashes of light in the area of the visual field, the apperance of specks in the eye or partial or full loss of vision. In these cases, we should see an ophthalmologist immediately.

Causes

The causes of the excessive increase in the size of the eye are unknown and unpredictable, although there is an unquestionable genetic component involved, meaning that a family history of myopia usually exists.

Types

We can divide myopia into two large groups: 

Simple myopia: It is myopia of less than 6 dioptres and it does not usually present with any complications. It occurs because of a discrepancy between the refractive elements of the eye, particularly the cornea, and the axial length. 

High myopia: It is also known as degenerative myopia, more than 6 or 8 dioptres and is more predisposed to causing complications and associated eye pathologies. In general, the higher the number of dioptres, the higher the risk of complications. Myopia with a very high prescription is also known as myopia magna. 

Prevention

High myopia cannot be prevented, that is to say, we cannot stop the excessive growth of the eye. What we can prevent, on many occasions, are the complications arising from it. For this reason, we recommend regular eye check-ups including an intraocular pressure test and an examination of the back of the eye.

Treatments

The treatment for myopia is based on optical correction of the refractive error with either glasses or contact lenses. 

While the surgical treatment of choice for simple myopia is usually excimer laser surgery of the corneahigh myopia can usually be corrected by surgically implanting intraocular lenses. 

Even though these surgical treatments are an excellent way of correcting the optical error, they cannot stop the possible progression of the myopia or rule out the possibility of complications of the retina. .

The treatment for retina complications involves laser photocoagulation of the lesions predisposing the patient to retinal detachment, and surigcal treatmnt if retinal detachment has already happened. If the neovascular membranes that cause haemorrhages appear, they can be treated with intravitreal injections.

Professionals who treat this pathology

Frequently asked questions

  • Simple myopia usually starts in childhood, it increases more rapidly in adolescence and usually begins to stabilise itself at the end of body development (18-22 years).

    High myopia usually increases more rapidly and stablises later in life. It's difficult to determine a set age as it will depend on many factors, the most important probably being the number of dioptres, that is to say, the higher the myopia, the longer it will take to stabilise. The majority of myopias do not usually increase consistenly past the age of 25, but a random increase beyond that age cannot be ruled out.

  • Any type of refractive surgery—be it laser or with intraocular implants—aims to correct the current myopia, which is done with great precision, however, currently there is no technique that can stop it from progressing. Therefore, surgery should be performed once the myopia is stable and the patient has gone a couple of years without any significant increase in their prescription.

    Once stable, the majority of myopias do not tend to change in adulthood, although cases of higher myopia do change more often than those of simple myopia.