Myopia is defined as a defect of sight (refractive error) in which nearby objects are clearly seen, but distant objects of the observer appear blurred (not clear vision).
Myopia occurs if the eyeball is too long or the cornea (the transparent front cover of the eye) has a very pronounced curvature.
The focus of the image happens in front of the retina (the part of the light sensitive eye) instead of directly happening in it, causing blurred vision.
As a result, light entering the eye is not focused correctly and distant objects appear blurred.
Generally, myopia begins in childhood. In most cases, myopia stabilizes when the person is about 20/25 years old, but sometimes it continues to worsen with age.
Types of myopia
Classification based on anatomical characteristics
The origin of axial myopia is the increase in the axial length of the eye.
Refractive myopia Refractive
myopia is linked to the condition of the refractive elements of the eye.
Refractive myopia is further divided into:
- Myopia of curvature is caused by excessive curvature of the cornea or lens,
- Index myopia is caused by the change in refractive index of the lens, for example in the case of cataracts .
Classification based on symptoms
Simple or non-pathological myopia
It is the most common and is characterized by an eye too long for its optical power. Simple myopia rarely reaches 10 diopters. There are no changes in the cornea or other ocular structures.
It is also known as malignant , progressive or pathological , and is characterized by changes in the posterior pole of the eye.
This type of myopia worsens progressively with time.
Degenerative myopia is one of the leading causes of visual impairment (disability) because the patient can reach a severe loss of vision .
Among the causes are:
It is a disorder characterized by difficulty seeing in low light conditions, but daytime vision is normal.
In a poorly lit room, the eye has increased accommodation.
Night myopia affects young people more than the elderly.
is a disorder caused by spasm (involuntary muscle contraction often accompanied by an increase in volume) of the ciliary muscle.
It is also called acquired or transient myopia and is the consequence of:
1. Some medicines (eg diuretics ),
2. High blood sugar ( hyperglycemia ),
3. Sclerosis of the crystalline nucleus,
4. Horizontal bands used to repair retinal detachment may induce myopia by increasing the length of the eye.
Deprivation myopia , for example, can develop because of a bandage applied to the eye for long periods.
Classification based on gravity
Less than 3 diopters.
Moderate to medium myopia
Between 3 and 6 diopters.
Affects about 30% of myopic people and is greater than 6 diopters.
People with elevated myopia are more likely to develop:
- Retinal detachment,
- Open angle glaucoma,
- Floaters (flying flies).
Classification based on age of onset
Also called childhood myopia, it is present at birth and persists during childhood.
occurs before the age of 20.
According to the scientists, the cause is heredity. In the past, it was thought that juvenile myopia was caused by too much study, because the young man always looked at nearby objects.
Myopia in adults
The onset of myopia in adults occurs after 20 years of age.
Causes of Myopia
According to conventional medicine, the causes of myopia are genetic and environmental .
According to Dr. d’Adamo and Mozzi’s blood type diet theory , vision defects in children are caused by the presence of milk and dairy products in the diet.
According to Shelton’s natural hygiene , myopia is caused by:
- Insufficient eye activity,
- Bad lifestyle,
- Power not suitable.
The structures of the eye are not hard and rigid, but flexible and can deform and adapt to environmental conditions.
The glasses reduce the adaptability (accommodation) of the lens and are therefore discouraged by hygienists.
Staying indoors and looking at nearby objects
Several studies show that to reduce or cure myopia outdoor activities are key.
A 2008 Australian study of 12-year-olds who performed a daytime outdoor activity program showed a reduction in myopia after 2 years.
Another scientific study conducted in Taiwan separated children aged 7 to 11 in two groups:
1) Children regularly practiced outdoor activities during recess,
2) Children were kept indoors during recess.
After one year, the results show that only 8.4% of the first group developed myopia, compared to 17.6% in the second group.
In addition, myopic children in the first group presented a worsening of 0.25 diopters compared to 0.38 of the second group.
Symptoms of myopia
Symptoms of myopia may include:
- Blurred vision when looking at distant objects;
- The need to tighten the eyes or partially close the eyelids to see clearly;
- Headaches caused by excessive eye fatigue ;
- Difficulties in vision while driving a vehicle, especially at night (myopia at night).
Myopia is discovered in childhood and is usually diagnosed between the first years of school and adolescence
A child with myopia can:
- Squinting continuously;
- Need to sit closer to the television, the movie screen or the front of the classroom;
- Keep the books very close to the face while reading;
- Do not see distant objects;
- Rub your eyes often.
Diagnosis of myopia
The ophthalmologist can diagnose myopia as part of a complete eye examination.
He or she determines if the person has myopia with a standard eye exam, in which the patient should read:
- The letters on a plaque on the other side of the room ( Snellen letter ),
- The sentences in the table (or letter) of Jaeger ; it is a leaf with large and small characters, that allows to evaluate the close up view.
If the test shows that the patient is myopic, the doctor uses some devices to understand what causes myopia.
It directs a special light against the eyes and then uses a retinoscope to see the light reflection in the retina.
Since the light is reflected inside the eye, it can indicate whether a person is nearsighted or suffers from presbyopia .
The doctor also uses a phoropter, an instrument that measures the severity of the refractive error and helps determine the correct prescription to correct it.
Treatment and lenses for myopia
The purpose of myopia treatment is to help focus the light on the retina through the use of corrective lenses or refractive surgery.
lenses Use corrective lenses to treat myopia by neutralizing the greater curvature of the cornea or excessive length of the eye.
The types of corrective lenses are:
Eyeglasses. The glasses are available in a wide variety of styles and are easy to use.
Eyeglasses can correct many vision problems at the same time, such as myopia and astigmatism .
Contact lenses . There is a wide variety of contact lenses:
- Rigid gas permeable (RGP),
- Bifocais lenses.
It is necessary to talk to the ophthalmologist about the pros and cons and what solution may be the best for the patient.
According to the hygienist Shelton , glasses are objects that can only make vision worse because, during their use, the eye does not try to make accommodation in the direction of difficulty.
Immediately after removing the glasses the patient sees even worse.
The body has an incredible ability to adapt, for example:
1. Sports performance improves with training,
2. After an ankle fracture , strength and balance improve with rehabilitation and exercise ,
3. The bone becomes stronger with standing physical activity while it becomes weak ( osteoporosis ) in sedentary people.
The conclusion is that to regain vision, Shelton advises to drop his glasses and force his eyes to see in conditions where they have more difficulty.
Often myopia glasses are recommended for young people over 15 years of age.
They could have sudden vision problems as a result of:
- Not suitable food,
- Stress ,
- Overworked on the computer.
Usually the ophthalmologist tells the patient to put the glasses to myopia given that the eyeball is too long, even if, in fact, until recently it was correct.
Surveys and news on myopia
There are many researches to find ways to control the progression of myopia in childhood.
Recently, researchers in New Zealand reported encouraging results with “dual focus” gel lenses designed specifically for the control of myopia in children.
The experimental lenses have a significantly lower power at the periphery of the lens relative to the center.
It is believed that this phenomenon may reduce the tendency for a greater elongation of the eye that causes the worsening myopia.
In a study published in 2011, researchers found that in 70 percent of myopic children (11-14 years) who used the experimental lens in one eye and a standard gelatinous contact lens in the other, the progression of myopia was reduced by at least 30 percent in the eye that used the “dual focus” contact lens.