Question

short note on astigmatism

Answer 1

Eye strain, also known as asthenopia (from Greek asthen-opia, ἀσθεν-ωπία, "weak-eye-condition"), is an eye condition that manifests through nonspecific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and occasional double vision. Symptoms often occur after reading, computer work, or other close activities that involve tedious visual tasks.

Answer 2

; a normal I can focus all the lights from any objects at the same point sometimes the light coming in horizontal and vertical plane do not come to focus at the same point as a result the horizontal and vertical waves of an object and not seen with the same clarity such a defect of eye is called astigmatism. A person suffering from astigmatism is not able to see in all the direction equally well due to this defect the image of a distant point object appear as a line on the retina.

Causes it occurs when the cornea are the islands or both are not perfectly spherical.

Correction it can be corrected by using cylindrical lens lens have different curvature in the horizontal and vertical directions.