Astigmatism (Greek. astigma = no stigma, no focal point) is an eye disease caused by a deformation of the cornea, which entails a defective refraction of the light ray in the eyeball.
In the case of astigmatism, white light rays arriving at the eye as parallel rays (eg from a distant object) undergo a complex and uneven refraction process. The more unequal this differential refraction is, the more severe the astigmatism is considered.
In humans, the eye with an astigmatism of up to 0.5 diopters (1 dpt = f-1) is considered normal.
FORM OF MANIFESTATION
While the image in the focal point of a distant light source has a spherical shape in the healthy eye, in the case of astigmatism an image consisting of two lines appears, due to the different refraction of the light rays. The further apart the two lines are, the more severe the astigmatism.
FORMS OF Astigmatism
Are regular shapes of astigmatism, when the two virtual images formed on the retina that can be located at different distances from each other according to the severity of the disease, but the images are always located on a vertical axis, while at irregular shapes the images are at a 90° angle or placed diagonally to each other.
CAUSE
Often the corneal bulge has an abnormal ellipsoidal shape, this deformation can cause myopia (short-sightedness), or keratoconus or keratoglobus which frequently occurs in both eyes frequently manifesting as myopia and less often as presbyopia (female/male ratio being 1:2).
Virtually all people have astigmatism. This is physiological astigmatism (0.50–0.75 dpt), for which no optical correction is required, being accompanied by normal vision. Existing from birth, it can be accompanied by a slight evolution and is called congenital. Astigmatism can also be acquired, one of the determining factors being surgery, but also various eye diseases, such as keratoconus and pterygium.
CONSEQUENCES
The image formed on the retina is blurred in the eye suffering from this condition and may appear even at birth (amblyopic which frequently occurs only in one eye), or later, being an irreversible form.
CORRECTION & TREATMENT
Optical correction of astigmatism can be done with glasses or contact lenses. Refractive surgery is used for permanent correction.
