What Are the Different Types of Astigmatism Glasses?

Astigmatism glasses are used to correct astigmatism. There are two types of astigmatism, regular as well as irregular. Irregular astigmatism cannot be corrected with optical spectacle lenses. Only rigid contact lenses can be effective. Regular astigmatism is corrected with optical spectacle lenses. Improve vision.

Astigmatism glasses

This entry lacks an overview map . Supplementing related content makes the entry more complete and can be upgraded quickly. Come on!

simple

(1)

One,
(1) Low

Principles of correcting astigmatism with ordinary spherical contact lenses

Ordinary spherical contact lenses use a tear lens to correct corneal astigmatism. A liquid lens composed of tear fluid between the rear surface of the contact lens and the front surface of the cornea is called a tear lens. But only when the corneal astigmatism is less than 0.75D, can the tear lens formed by ordinary spherical contact lenses be used for correction; beyond this range, custom astigmatic contact lenses are required.

Custom astigmatism contact lens correction astigmatism principle

When corneal astigmatism is greater than or equal to 0.75D, ordinary spherical contact lenses cannot be used to completely correct astigmatism contact lenses (astigmatism contact lens custom lenses) to correct astigmatism, while non-corneal astigmatism (mainly caused by lens astigmatism) is also corrected. This can be corrected by customizing astigmatism contact lenses.

Astigmatism contact lenses refer to contact lenses with hyperboloids (inner and outer surfaces) with two mutually perpendicular meridional azimuths with different radii of curvature. They are also called toric contact lenses. The most important design of custom-made astigmatism contact lenses is the stability of the lens, because only astigmatism can be stabilized in the axial direction to correct astigmatism. In general, there are three principles of stabilization of custom astigmatism contact lenses:

A. Prism vertical method. A prism of 1 ~ 1.5 is designed on the lens. Due to the relationship of gravity, the thick side of the prism always moves to the downward direction to keep the lens stable. In addition, the lens prism base increases the thickness, and the oxygen conductivity of the thicker lens area is reduced, reducing comfort.

B. Bilateral thinning method. The upper and lower peripheral areas of the lens are thinned. The thin areas interact with the eyelid (especially the upper eyelid) to position the lens and make the axial position stable and dynamic. (This is the most commonly used method.)

C. Trimming method. A part of the lower part of the lens is cut, and the width is about 0.5 ~ 1.5mm, so that the missing part is fixed on the edge of the lower eyelid to prevent rotation.