Eye diseases: characteristics, types and symptoms

Visual problems are present in a large percentage of the world population, having been increasing during the last decades and presbyopia being the most common of the eye diseases from the age of 40 years.

Eye diseases such as myopia, hyperopia and astigmatism, constitute vision problems related to defects in the visual refraction, which make it difficult for the person suffering from them to be able to clearly perceive perceived objects that are at a certain distance.

There are also other eye diseases that cause many problems in the lives of those who suffer from them, such as cataracts and glaucoma, while there are diseases that do not cause so many difficulties on a day-to-day basis, such as colour blindness.

Here you will find a summary of the most important eye diseases, classified.

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What are the main eye diseases?

Visual refraction consists of a process in which light, which comes from external objects, passes through the various parts of the eye

, a place where photoreceptor cells are found (the rods and cones), which are They are responsible for converting the light from objects into nerve impulses that reach the brain for him optic nerve, to transform into images.

So, after this process, the images of the objects are concentrated on the retina.

In cases where these rays of light are projected on the retina at only one point, so that the image created is sharp, we would be talking about a correct refraction process, which makes an emmetropic eye that does not present any pathology with respect to the vision refraction.

On the other hand, if there is a problem in this process of visual refraction, so that the eye is not able to focus sharply on the images on his retina, suffering from blurred vision towards objects or people who are at a certain distance, we would talk about a refraction problem.

Depending on the distance at which this difficulty is present to perceive objects and people clearly, we would speak of one pathology or others.

Next we will see the most common visual pathologies, classified.

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Vision diseases related to visual refraction

The diseases of the eye that occur due to some difficulty in the process of visual refraction will be explained below.

1. Myopia

The visual pathology known as myopia is characterized by having a blurred vision of objects that are at a far distance, presenting the person who suffers a correct vision in short distances.

This is caused because a myopic eye is more elongated than a "normal" or emmetropic eye, so the rays of light coming from the Perceived objects converge in front of the retina, rather than on it, so that images are out of focus.

No matter how much a myopic person tries to focus sharply on a distant object, they will not achieve it, the only way that he can correctly perceive the image of distant objects is by using divergent lenses or glasses, although too can be treated by a surgical operation performed by a specialized ophthalmologist with the help of his team known as refractive surgery, which also help correct hyperopia and astigmatism.

Another important aspect to take into account in these visual pathologies is their degree of severity. Said severity is measured in units known as diopters, therefore, the higher the degree of severity of myopia a person has, the number of diopters in which it will be measured.

However, the degree of severity based on the number of diopters, both for myopia and for hyperopia and astigmatism, must be diagnosed by a medical professional after having performed the corresponding tests on the patient, this classification being applied for guidance, based on the sources consulted.

The degree of myopia tends to increase as the person becomes older., being key its detection as soon as possible in order to worsen the degree of severity as little as possible.

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2. Farsightedness

Other eye diseases related to visual refraction is hyperopia, which is It occurs when the rays of light projected into the eye, which come from perceived external objects, intersect at the back of the retina, whereas they should cross the same.

A person with farsightedness can clearly see objects that are at a far distance; instead, blur objects that are at a close distance. This visual refractive error occurs because the length of the eyeball is shorter than that of a "common" or emmetropic eye.

However, hyperopia, unlike myopia, can compensate for its refractive error, in part, by increasing the diopter power of the lens, the part of the eye that is between the iris and the vitreous humor; whose function is to focus the objects perceived outside.

Therefore, a person with mild or moderate hyperopia and can have correct vision thanks to the increased capacity of the lens, so that the rays of light that pass through the eye, coming from objects perceived outside, are correctly focused on the retina without producing a vision blurred.

Secondly, Although the lens can compensate for the visual refractive problems of people with hyperopia, it is advisable to wear glasses in order that the person does not strain their eyes too much because they may suffer other problems such as eye strain, headaches and even eye strabismus. In addition to the fact that, in the case of hyperopia with a high degree of severity, the lens will not be able to compensate for the visual refractive error, so that the person will see all images blurry distances.

Farsightedness, if detected early, it does not tend to worsen in severity over the years, in case of being detected at an early age.

On the other hand, with the use of corrective glasses, in addition to being able to see correctly, during the child's development stage, it tends to increase the length of the eyeballs and, with it, the number of diopters will decrease, which may become insignificant when reaching age adult.

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3. Astigmatism

A large percentage of people with farsightedness or myopia also tend to have some degree of astigmatism.

When a person has astigmatism perceives an out-of-focus image of objects (p. g., perceive the edges of objects with poor definition), occurring for both distant and near objects, that is, the person has difficulties to see subtle details of objects, both at close and distant distances. far away.

Astigmatism is a visual pathology that occurs when diopter visual surfaces (cornea and lens) do not have the same curvature or convergence capacity in all their axes (p. g., the horizontal and vertical axis of the cornea are asymmetric).

The degree of severity of astigmatism does not normally change very noticeably during the stage of growth of the person, unlike what happens with myopia or hyperopia that is accompanied.

In addition to the visual pathologies discussed above, there is another pathology related to visual refraction which is very frequent among the adult population, so it is convenient to comment on what it consists of. continuation.

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4. Presbyopia (eyestrain)

Due to a common evolutionary aging process, the lens decreases its ability to focus on objects coming from outside on the retina, produced by a weakening of its ciliary muscles, so that most of the people from a certain age lose that ability to focus correctly without the use of contact lenses.

It is common for presbyopia to start from 40-45 years of age, although in some cases it may appear at an older age.

Other common eye diseases

Other eye diseases will be briefly explained below which, although they are less frequent than those related to visual refraction, they also occur in many of cases.

1. Color blindness or dyschromatopsia

This visual disease causes the subjects who suffer from it to have ugreat difficulty distinguishing between certain colors, because they have 2 types of cones when they should have 3.

There are 3 types of dyschromatopsia:

• Protanopia: due to the lack of L cones, they do not distinguish well between green and red.
• Deuteranopia: due to the lack of M cones, they also do not distinguish well between green and red.
• Tritanopia: due to lack of S cones, they do not distinguish well between yellow and blue.

Deuteranopia and protanopia are eye diseases that occur more frequently in men than in women., because they are produced by genetic causes that are linked to the X chromosome.

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2. Open angle glaucoma

Of the group of eye diseases that cause damage to the optic nerve, glaucoma is the most common, whose damage is, specifically, in the open angle of the optic nerve.

The way glaucoma causes damage to the open angle is when aqueous humor (liquid that nourishes and oxygenates the cornea and lens) is not able to drain effectively, so that fluid accumulates and with them increases the pressure in the eye, so that the optic nerve is damaged.

At the moment that the nerve fibers of the optic nerve begin to be damaged, they die and the person begins to develop blind spots in visionThe so-called “tunnel vision” is frequent, which prevents the subject from having a peripheral vision of the environment, so that there are more blind spots in his vision than would be normal.

Therefore, the two most common symptoms of this visual disease are:

• Tunnel vision.

• Having blind spots in side or peripheral vision.

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3. waterfalls

This eye disease occurs when a cloudiness is perceived in the lens, instead of being totally transparent, so that it does not allow the lens to focus the light well coming from perceived objects to focus them correctly on the retina, so there is blurred vision. In addition, it is an eye disease that is increasing if it is not intervened in time.

The most common vision changes that allow a person to detect that they might have cataracts are the following:

• See blurry.
• Double vision.
• Serious difficulties to see at night.
• Have sensitivity to light.
• Perceiving lights dimmer than normal.
• Perceive bright colors in a subdued way.

This disease can prevent the person from performing tasks such as reading or driving a vehicle, among others, and can also make it difficult to recognize the facial expressions of other persons.

Fortunately, to this day, there are effective surgical methods that allow to solve diseases of the eye like this.

Cataracts are a disease whose probability of appearing in people increases proportionally with age.