What can cause a permanent blurring of vision for either horizontal or vertical lines?

Question

Quizplus · Accepted Answer

Asymmetric curvature of the eyes can cause astigmatism, which is a refractive error that results in blurred vision for either horizontal or vertical lines. This can be corrected with corrective lenses or surgery. Pressure on the optic chiasm can cause visual field defects, but usually affects both horizontal and vertical lines. Weak muscles controlling the lens of the eyes can cause difficulty with focusing, but would not result in permanent blurring of vision. Damage to the corpus callosum can affect communication between the two sides of the brain, but would not directly cause visual disturbances.

What Can Cause a Permanent Blurring of Vision for Either