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Visual acuity: standard, diagnostic and low vision

visual acuity

The ability of the eye to see and distinguish between two adjacent objects is called visual acuity.

With normal visual acuity, two dots can be seen at a distance of 5 metres. The distance between these points is 1.45 mm. If your vision is impaired, you will not be able to pass this test.

Deviations from the reference value (1.0) may occur either naturally or as a result of ageing. However, it is not uncommon for vision to deteriorate and decline rapidly at an early age, even in children. The reasons for this are mass computerisation and the development of various diseases.

Index below 1.0 – what it means
Complex tests are carried out to find the cause of the sudden change.

Usually, a visual acuity index below 1.0 indicates the presence of a progressive disease:

The most common condition is myopia.
A change in visual acuity is accompanied by a decrease in the ability to distinguish distant objects, rapid fatigue, itching and headaches:

A condition in which the image is focused behind the retina. As vision deteriorates, a person is unable to see near objects clearly. Perception is impaired, resulting in blurred vision and strabismus.

The lens and cornea become irregularly shaped and vision deteriorates rapidly. Images become distorted, objects appear far away and headaches occur.

Develops when intraocular pressure deviates from the norm. A decrease in intraocular pressure causes deformation of the internal structures of the visual organs, resulting in retinal dystrophy. If the optic nerve is severely damaged, this diagnosis leads to total blindness.

This is a clouding of the lens of the eye. As the disease worsens, a person becomes painfully sensitive to light and has difficulty distinguishing colours. Difficulties with reading and orientation in twilight. Unsuitable working conditions, harmful production and constant loss of attention often lead to deterioration of vision. Eye disease can also occur in children. In this case, the loss of good vision is often associated with hereditary diseases. Basic rules for testing visual acuity Visual acuity is tested using a special chart with letters and numbers. The test is carried out by an ophthalmologist or an optician who sells glasses and lenses. If there are signs of eye pathology, diagnosis and treatment should be continued.

For adults, a chart with letters is used; for children who cannot yet read, a chart with symbols is used; as a standard, 10 out of 12 lines should be clearly visible and readable. Based on this diagnosis and other tests, it is possible to understand the cause of the visual impairment and the most appropriate treatment.

The basic rules for vision testing

visual acuity

The test person sits at a distance of 5 metres from the table. The picture is viewed from the opposite window. The tenth line of the chart is exactly opposite the eye. The examination table is lit by a special
lamp. One eye is open, the other eye is closed but not shut (this affects the clarity of the signs and the accuracy of the results). Recognition of letters and symbols in 2-3 seconds.

How to test at home

If necessary, a preliminary assessment can be carried out at home. In this case, various online tests can help, the results of which are displayed at the end. Tables can also be used for testing, as in ophthalmology. Examples of charts can be found on the internet and printed out on normal A4 paper. The resulting chart should be hung on the wall. Install a fluorescent lamp or two lamps (40W) on each side of the table. The first change or deviation from the norm is indicated by the inability to see letters or symbols in line 10. In this case, an appointment with an ophthalmologist should be made immediately.

Dangerous symptoms

Black veil or black threads.
One of the first signs of reduced vision, indicating the onset or progression of the disease, is a black veil or threads covering the eye. This symptom indicates a detached retina. If the condition of the eye is not treated immediately, it can deteriorate rapidly. Immediate hospitalisation is necessary.

Image distortion and blurring.
Straight lines appear distorted. You need to see a doctor to find out what is causing your vision to deteriorate. Vision loss can be caused by age-related changes or damage to the retina. Vision loss often manifests itself as a lack of brightness or contrast, or as blurred vision. This is caused by a clouding of the lens, a sign of cataracts. This condition can lead to blindness.

Reddening of the mucous membranes, severe pain, “mist” in the eyes.
In particularly complicated cases, nausea and vomiting may occur. These can all be signs of glaucoma. What to do with these symptoms – Urgent emergency treatment is needed and, if complications arise, surgery.

visual acuityLoss of vision.
The degree of damage to the optic nerve depends on the severity of the symptoms. The disease is dangerous because it can lead to glaucoma and removal of the visual organ.

Dark spots, cloudiness.
These symptoms usually occur with retinal lesions, retinal haemorrhages. This condition may cause blindness.

Dryness, burning, watering tears.
In this case, the cause of the deterioration in vision is constant overwork and overstress. This condition is particularly characteristic of people who spend a lot of time at the computer and working with documents.

With deteriorating vision, life becomes less pleasant and many diseases appear. Regular (at least twice a year) eye examinations are necessary for early detection and successful treatment of the problem. Risk groups include people with a family history of genetic predisposition. Vision is often impaired after trauma, such as an injury to the upper cervical spine. Many diseases develop from diabetes, cervical osteochondrosis and genetic disorders. The organs of the elderly undergo changes. Early medical attention and diagnosis are the most important steps for a speedy recovery.