Cylindrical lenses have astigmatism. A cylindrical lens of -0.75 indicates that the astigmatism of the right eye is 0.75. Cylindrical lenses are used to correct astigmatism. Ametropia is divided into myopia, hyperopia and astigmatism, which are corrected by concave lens, convex lens and cylindrical lens respectively. Cylindrical lens is made by cutting cylindrical lens into a circle, which is called cylindrical lens for short.
Cylindrical mirror is often used for astigmatism correction of astigmatism eyes, so it is also called astigmatism mirror, and "-"stands for myopia astigmatism; "+"stands for hyperopia astigmatism.
Extended data:
Abnormal vision
1, myopia
The professional definition is that "distant objects are refracted by the eyeball and focused in front of the retina, rather than forming a clear image on the retina". Myopia is the most common eye disease among children in China, and the high myopia rate in Chinese mainland is much higher than that in other countries and regions. Many eye diseases caused by high myopia are threatening the eyesight and eye health of many children.
2, hyperopia
Nearby objects are refracted by the eyeball and focused on the back of the retina, forming a blurred image on the retina. So hyperopia patients can't see clearly. Myopia in infants is rare. More than 90% of preschool children are hyperopia, most of which are physiological, reflecting the normal development of eyes. 20% ~ 25% hyperopia is pathological, which is the main reason for children's poor eyesight and eye dysplasia.
3, amblyopia
Amblyopia is a disease that seriously affects visual function. It refers to those who have no obvious organic lesions in the eyeball, and their near and far vision is less than 0.8, so they can't drive straight.
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