What does “400 degrees of astigmatism” mean?
Jun 29, 2022
Source: Cainiu Health
Dr. Chen You
Introduction
Clinically, astigmatism exceeding 400 degrees is termed high astigmatism; patients with high astigmatism experience a greater impact on visual acuity. First, it is essential to understand the concept of astigmatism: a normal cornea is spherical—resembling a basketball—with nearly identical radii of curvature in the horizontal, vertical, and oblique meridians, allowing the refractive system to produce a single focal point. In contrast, an astigmatic cornea may be shaped more like a rugby ball (i.e., toric).
Whether astigmatism is severe depends on its degree. If the astigmatism is mild, it has minimal impact on vision and is therefore not considered serious. However, high-degree astigmatism is more severe and challenging to treat. So, what does “400-degree astigmatism” mean?
What Does 400-Degree Astigmatism Mean?
In clinical practice, astigmatism exceeding 400 degrees is classified as high astigmatism. Patients with high astigmatism experience greater impairment of visual function. First, it’s important to understand the concept of astigmatism: a normal cornea is spherical—similar in shape to a basketball—with nearly equal curvature radii in the horizontal, vertical, and oblique meridians. This uniform curvature allows light rays to converge into a single focal point after passing through the eye’s refractive system. In contrast, an astigmatic cornea resembles a rugby ball or American football, where the horizontal and vertical curvature radii differ, resulting in two distinct focal points.
Key features of high astigmatism include poor distance and near vision, difficulty achieving optimal visual correction, and a tendency to develop symptoms such as visual confusion, compensatory head posture, and eye strain. Patients with 400-degree astigmatism may attempt correction using eyeglasses; tolerance for maximum astigmatic correction should serve as the benchmark, with careful attention paid to balancing correction between both eyes. Eyeglasses are the primary option, but rigid gas-permeable (RGP) contact lenses may also be tried—some patients achieve superior visual outcomes with them. For adult patients considering surgical intervention, laser refractive surgery is another viable option.
Patients are advised to avoid rubbing their eyes with their hands, minimize prolonged screen time on electronic devices, and spend more time outdoors viewing greenery. We hope this information proves helpful.
