How to Choose Eyeglasses for Astigmatism Combined with Myopia
Jun 29, 2022
Source: Cainiu Health
Dr. Chen You
Introduction
Astigmatism combined with myopia makes eyeglass prescription quite complex and requires comprehensive consideration of astigmatic power, axis, and myopic degree. If the astigmatism is minimal—less than 50 diopters or only mild—it can be directly incorporated into the lens during manufacturing; thus, separate cylindrical and spherical lenses need not be adjusted. However, if the cylindrical component of the astigmatism is relatively large…
Generally, when myopia (nearsightedness) or hyperopia (farsightedness) occurs, corrective eyeglasses can be worn to improve vision, enabling clearer sight of distant or near objects. Astigmatism is a type of refractive error in the eye, commonly associated with irregular curvature of the cornea. When astigmatism is present, symptoms such as reduced visual acuity and eye strain often occur. So, how should glasses be prescribed for individuals with both myopia and astigmatism?
How to Prescribe Glasses for Myopia Combined with Astigmatism
Prescribing glasses for coexisting myopia and astigmatism is relatively complex and requires comprehensive consideration of the astigmatic power, axis, and degree of myopia. If the astigmatism is mild—less than 50 diopters—it can typically be incorporated directly into the lens during manufacturing; thus, separate cylindrical and spherical lenses are unnecessary. However, if the cylindrical component is relatively large, integrating spherical and cylindrical corrections into a single lens becomes technically challenging. Some cases involve mixed astigmatism, where the cylindrical power may even exceed the spherical power. In such instances, precise localization must be attempted prior to lens conversion or prescription.
When prescribing glasses for myopia combined with astigmatism, both spherical lenses (to correct myopia) and cylindrical lenses (to correct astigmatism) can be incorporated into the same pair of spectacles. During prescription, the myopic correction is generally fully addressed, while the astigmatic correction is adjusted according to the severity of astigmatism. If astigmatism is minimal and the patient maintains good visual acuity without significant eye strain, cylindrical correction may be omitted. Conversely, if astigmatism substantially impairs vision and causes noticeable eye strain, cylindrical lenses should be included in the prescription.
When selecting cylindrical lenses for astigmatism, it is advisable to start with the lowest possible power and gradually increase only to the minimum level that provides clear, comfortable vision for the patient. We hope this explanation proves helpful.
