Visual acuity testing

Visual acuity testing, a modern ophthalmological examination method, allows a doctor to determine a patient's visual acuity with the necessary precision. Based on the data obtained, the ophthalmologist selects the type of glasses or contact lenses, establishes restrictions on professional activities, and so on.

The method makes it possible to measure the eyes' ability to distinguish two points at the smallest angle. In a normal state, this angle equals one. Special objects (optotypes) are used in visual acuity testing, the most famous of which is the Sivtsev-Golovin chart featuring letters of the Russian alphabet. You can undergo visual acuity testing in Moscow at the Okomed clinic: http://www.okomed.ru/visometriya.html.

How is a visual acuity test conducted?

Initially, relative visual acuity is determined, which depends on several parameters. For this purpose, visual acuity testing is performed without optical correction.

Subsequently, absolute acuity is measured. The test results are recorded as a fractional value, where the first number represents the distance to the object, and the second – the distance from which a person can distinguish it.

The accuracy of visual acuity diagnostics directly depends on adherence to the conditions under which it is conducted. To achieve an optimal result, specific display times for the object, the distance to it, and the lighting level must be observed.

Initially, the specialist checks monocular visual acuity (alternatingly in each eye), followed by binocular acuity. If difficulties arise in identifying optotypes, the test is reduced to counting the number of fingers the ophthalmologist displays from various distances. If this also proves difficult, the ability to determine the direction of optical radiation is assessed. This type of diagnostics can reveal whether the functionality of the central optic nerve and the retina is preserved. Establishing this fact is necessary when treating cataracts and other pathologies of the optical system.

How is visual acuity testing conducted in children?

Visual acuity testing is indicated for patients of different ages, with the determination of visual acuity in children having several specific features:

• this type of diagnostics largely relies on the analysis of behavioural factors;
• bright balls or charts with images that can attract a child's attention (for example, featuring animals) are used as optotypes;
• the optokinetic nystagmus method is additionally applied to rule out the fact of simulation.

According to data from the Okomed clinic