​What is the highest degree of astigmatism

There is no specific number of astigmatism heights available, but generally, astigmatism above 200 degrees can be called high astigmatism. Generally, glasses with astigmatism above 200 degrees need to be custom made for the manufacturer who makes the glasses. In fact, a temperature over 1000 degrees is a very high level, but in daily life there are not many people whose temperature exceeds 1000 degrees. It is recommended to go to the hospital for examination and relevant treatment.

1. Unequal curvature

That is, the curvature of the refractive surface of the eye is inconsistent, which often occurs in the cornea but can also occur in the lens. Mild astigmatism is considered physiological. The most common condition is that the vertical curvature of the cornea is greater than the horizontal curvature, usually about 0.2D. It is caused by frequent compression of the upper and lower eyelids. This physiological defect tends to increase slightly with age.

People with larger degrees of astigmatism are mostly congenital, while acquired astigmatism is often caused by corneal diseases. For example, keratoconus, peripheral corneal degenerative diseases or scars left after corneal inflammation often cause irregular astigmatism. In addition, irregular astigmatism can also be caused by cataract surgery or eyelid tumors pressing on the eyeball.

2. Optical center deviation

Most of the time, it is caused by disease or trauma, which causes the lens to be subluxated or significantly deviated, and the astigmatism is very obvious.

3. Unequal refractive index

It is caused by differences in the refractive index of different areas of the lens. For example, changes in the refractive medium caused by cataracts can lead to various astigmatism, visual distortion, and polyopia.

Clinical manifestations

1. Decreased vision

Visual acuity loss is closely related to the degree and type of astigmatism. People with mild astigmatism usually have normal vision, while those with moderate or high astigmatism have poor vision at both far and near distances. Simple astigmatism will cause a slight decrease in vision, while compound astigmatism and mixed astigmatism will cause a significant decrease in vision. If it is not properly corrected, amblyopia may occur.

2. Visual fatigue

Blurred images on the retina require constant fine-tuning, and vision is distorted, so patients with astigmatism, especially those with hyperopic astigmatism, are prone to visual fatigue. Symptoms include eye pain, tearing, headache, especially in the forehead, double vision, and inability to work at close range for a long time.

3. Compensatory head position and squinting

People with highly asymmetric astigmatism in both eyes often tilt their heads in order to see more clearly, which leads to strabismus. The astigmatism can be restored after correction. In order to obtain a larger retinal image, patients sometimes hold objects close like myopic patients. People with high astigmatism often squint when looking at distant or near targets, achieving the effect of pinholes and slits to improve vision. Looking through a pinhole or slit can reduce the effects of astigmatism on vision.