Myopia astigmatism

Introduction Myopic astigmatism, also known as simple myopic astigmatism, refers to parallel rays entering the eye. Parallel rays on a major meridian are imaged on the retina, and parallel rays on the other meridian perpendicular to it are imaged in front of the retina. This is myopic astigmatism. The focus on the retina reflects parallel rays, which are focused in front of the retina and reflect the collected light, so they are corrected by a concave cylindrical mirror. In addition, changes in the refractive index of each part of the lens can also be caused.

Cause

Different degrees of curvature of the corneal surface are the main causes of regular astigmatism, mostly congenital factors, and the degree of astigmatism is large. Some mild astigmatism is only about 0.25D, which may be the result of pressing the eyeball on the upper eyelid. It is a physiological range and generally does not need to be corrected. Most of the acquired myopic astigmatism is caused by the cloud surface of the cornea, corneal degeneration, keratoconus, and some operations such as corneal transplantation, strabismus correction, and pterygium excision.

an examination

Related inspection

Astigmatism optometry near vision test fundus fluorescein angiography binocular balance check fog vision optometry

In simple myopic astigmatism, when a parallel ray on a major meridian is imaged on the retina and parallel rays on another meridian perpendicular to it are imaged in front of the retina, we call this refraction state a simple myopic astigmatism. Refractive myopic astigmatism. If two parallel main rays are imaged in front of the retina, but their refractive power is not equal, we call this myopic astigmatism refractory myopic astigmatism. Whether it is simple myopic astigmatism or refractory myopic astigmatism, it is possible to improve the vision by wearing a cylindrical lens after optometry.

Differential diagnosis

Hyperopia: It is the parallel light that enters the eye and forms a focus behind the retina. The external object cannot form a clear image in the retina. The subjective feeling of the patient is far from blurred, and the nearer is more blurred. Use a convex lens to correct hyperopia.

Myopia: It is the parallel light that forms the focus in front of the retina after entering the eye. The external object can not form a clear image in the retina. The patient's subjective feeling is far blurred, and the near-eye is clear. The concave lens is used to correct myopia.

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