A disease that is manifested by total or partial impossibility of color perception. The reason for this disease is a very small or zero number of suppositories, which are responsible for seeing colors and sharpness of view. It is a genetic disease, although it may also occur as a result of injury or other eye diseases.
Incorrect vision due to distorted eye curvature. Astigmatism occurs when the eye is wider than height. Then the cornea and lens - instead of concentrating light in the round space of the retina, create a blurred image in one of the directions.
There are two types of astigmatism:
* astigmatism regular - the eye has two optical axes. This defect can be corrected by glasses with cylindrical glasses. * astigmatism irregular - the cornea of the eye is damaged as a result of injury. In this case there are more optical axes than two. The defect can be modified using corneal gels or contact lenses.
A defect characterized by impaired color perception. Red and green colors are not differentiated at the same time, but other colors may also be disturbed. Daltonism occurs mainly in men. Myopia This is the most common refractive error of the eye. The damage is manifested by the eye concentrating light rays in front of the retina. As a result, the image on the retina is blurred and makes vision distant.
Corrective glasses or contact lenses (diffuse / concave lenses) are used to correct myopia. Their optical power is denoted in diopters with a minus sign.
There are three degrees of myopia:
* small - up to 3 diopters
* moderate - less than 6 dioptres
* high - more than 6 diopters
The damage is manifested by concentrating the light rays behind the retina. Correction glasses or contact lenses (convex lenses - couplings) are used to correct hyperopia. Their optical power is denoted in diopters with a plus sign
Nystagmus (involuntary eye movements)
Defect manifested by uncontrolled, involuntary oscillations of eyeball.
We distinguish these types of nystagmus:
Diseases manifested by eye muscle weakness. As a result, the angle of vision of one eye changes with respect to the other. Streaking results in impaired stereoscopic vision. Squint can be corrected with glasses and exercise. Surgical corrections of strabismus are also performed.
Strabism is divided into:
* divergent strabism (divergent) - the eyes face outside the viewing angle,
* converging strabism (converging) - the eyes face the angle of view