The 8 types of myopia: causes and symptoms

Myopia is an alteration in the refraction process of the eye., the image is formed before reaching the retina, which means that objects that are located far away cannot be perceived well and are blurred.

We will classify different types of myopia according to the cause, linked to alteration of different ocular structures, such as the cornea, the lens or the eyeball or according to the severity of the condition, we will consider it simple if the diopters do not reach 6, that is, it is less serious, instead we will say that it is magna if they exceed 6 diopters and it is linked to a pathology ocular.

Treatment can also vary depending on the characteristics of the disorder or the subject. Simple myopia can be corrected with glasses, contact lenses or surgery. For its part, high myopia will need continuous control of the state of alteration to prevent it from leading to more serious conditions and to be able to treat related eye pathologies.

In this article we will talk about myopia, what types exist, what their main characteristics are,

its causes, prevalence, symptomatology and possible treatments.

• We recommend you read: "Surgery against myopia: procedure, prices and results"

What is myopia?

Myopia is an eye condition that is caused by an alteration in the process of refracting light on the retina. When the eye functions normally, the perceived image is focused on the retina, while in subjects with myopia, it is focused earlier. This variation in refraction appears when the object we observe is far away, the individual will see it blurred.

There are different levels of affectation, different graduations, making the subject see more or less blurry. In the same way, each eye is independent, which means that one of them may have myopia and the other may not. Although the most common is that if one shows refraction problems the other also has, and the degree can vary.

How are myopia classified?

We can differentiate different types of myopia that will show different characteristics while maintaining the essential features of the condition. Thus we will differentiate according to the cause and according to the degree of alteration.

1. Depending on the cause

We will classify different types of myopia according to which part of the eye is altered and if the pathology is present from birth or is acquired.

1.1. congenital myopia

As its name indicates, congenital myopia is seen in children from birth, shows genetic causes linked to a pathology of the mother or to the premature delivery of the baby. The causes are related to structural problems of the eye and usually show serious alterations although they do not have a tendency to worsen.

1.2. axial myopia

Axial-type myopia occurs when the eyeball is longer than normal, more than 24 millimeters. The eyeball is more oval, which means that the image does not refract on the retina and is projected earlier.

1.3. curvature myopia

Curvature myopia is related to an increased curvature of the cornea, which is a transparent layer that covers the iris, the pupil and the anterior or lens chamber, which is a lens located between the iris and the vitreous humor. Both structures allow the refraction of the image. The increase in curvature is therefore linked to a refraction of the image before reaching the retina.

1.4. index myopia

The appearance of index myopia is related to an increase in the diopter power of the lens, linked to the ability to modify the curvature shown by this structure of the eye in order to adjust and focus the image. This process is known as accommodation. Thus, if the power is increased, the curvature will increase, making it difficult to focus and producing blurred vision of distant objects.

1.5. mixed myopia

In the case of mixed myopia, more than one structural affectation of those mentioned above is observed.

1.6. false myopia

False myopia, as we can deduce, it is not truly considered a myopia, since it does not observe structural alteration. As we have already said, structures such as the lens allow the image to focus thanks to its variation in curvature, a process known as accommodation. Well, in false myopia the problem is linked to alteration in accommodation, we observe that the lens continues to be tense, contracted, when looking at distant objects. In this way, blurred vision will be shown due to the difficulty of relaxing the ocular muscles and due to the consequent greater curvature.

Typically the causes of this transient focusing difficulty is due to being exposed to low light conditions or by excess accommodation linked to trauma or diseases that affect the entire body such as diabetes.

Since the distinction is linked to the alteration or not of the internal structures of the eye, it is difficult to differentiate between a false myopia and a true one. A characteristic that can indicate it to us is a great variation of diopters, either in increase or decrease, in a short period of time. Likewise, if with the administration of cycloplegic drops we see that the problem decreases or disappears, it is highly likely to be linked to false myopia.

2. according to graduation

However, the distinction that is made most frequently is according to the graduation of myopia, that is, taking into account the severity of the alteration.

2.1. simple myopia

Simple myopia is the most frequent and is normally related to a degree of diopters less than 6. That is to say, it is less serious and is linked to a lower probability of showing ocular pathologies with respect to to other types of myopia, but it does present a higher risk of complications if we compare with the population normal. It usually begins before the age of 5, increases during adolescence and stabilizes after 18 or 20 years.

Being shown from such an early age, children may always remember having seen poorly, therefore for them the blurred vision of distant stimuli will be normal. They may use strategies to try to improve vision, such as squinting to achieve focus or getting closer to the target to reduce the distance and not see it from afar.

In addition, We cannot prevent this type of myopia. although if we remain attentive to possible indicators already mentioned that children may show, we can ask for the realization of an eye exam and correct with the most appropriate treatment either with glasses, contact lenses or refractive surgery, as long as the diopters are already stable, you have the right graduation to intervene, you are over 18 years old and you are in good health ocular.

There are two types of refractive surgery: laser, which, as the name indicates, the intervention consists of the use of a laser that impacts on the cornea in order to recover the ability to focus and the intraocular, which consists of implanting a phakic intraocular lens, placing it inside of the eye, between the iris and the lens and remaining indefinitely, performing the function of correcting the refractive problems linked to the myopia.

2.2. high myopia

Magna myopia or high myopia is less frequent and shows a greater alteration than simple myopia, with more than 6 diopters and produced by an abnormal increase in the length of the eyeball greater than 26 millimeters. It is hereditary, is seen more frequently in women and usually begins in childhood, usually before the age of 10. It is common for an increase in alteration to occur over the years.

As we have mentioned, it is more serious than simple myopia, thus being linked to eye diseases such as: early cataracts; glaucoma, a condition that damages the optic nerve; retinal detachment; or alterations in the macula, which is the center of the retina, sensitive to light. Individuals with high myopia may report vision loss and perceive straight lines as wavy. Given its status as an eye disease and the possibility of progressing to a larger condition, it is It is necessary to carry out regular check-ups with the ophthalmologist in order to prevent further alterations. future.

If high myopia worsens, it is considered pathological or degenerative myopia.. In this case, apart from the typical alterations of high myopia, we observe changes in the retina and a narrowing of the sclera, which is an outer layer that protects the eye from environmental damage and helps maintain pressure ocular. The symptoms of this myopia are low vision or even blindness. It is currently one of the main causes of blindness worldwide and its prevalence has increased.

The seriousness and pathologies linked to high myopia and the possibility of leading to more serious alterations means that, as we have That said, it is essential to carry out routine checks to verify that the situation does not worsen and thus be able to act in a early. The treatment that is carried out will be the one linked to the pathology with which it shows a relationship, such as cataracts.