Thelansis

  Astigmatism, a prevalent refractive error, is characterized by alterations in the refraction of light in different eye meridians. This condition results in the failure of parallel rays of light passing through the cornea to converge on the retina at a single focal point. Astigmatism can manifest as either regular or irregular. Typical symptoms include asthenopia, discomfort, blurred and defective vision, elongation of objects, and difficulties with accommodation. Signs of astigmatism include partial lid closure, head tilt, vertically oval or tilted optic disc, and varying power in different meridians. The underlying causes of astigmatism can be attributed to corneal, lenticular, or retinal factors. Regular astigmatism can further be classified into "with the rule" astigmatism, "against the rule" astigmatism, oblique astigmatism, and bi-oblique astigmatism. The principles of Sturm's conoid elucidate the optics of regular astigmatism. In regular astigmatism ca...

  Astigmatism, a prevalent refractive error, is characterized by alterations in the refraction of light in different eye meridians. This condition results in the failure of parallel rays of light passing through the cornea to converge on the retina at a single focal point. Astigmatism can manifest as either regular or irregular. Typical symptoms include asthenopia, discomfort, blurred and defective vision, elongation of objects, and difficulties with accommodation. Signs of astigmatism include partial lid closure, head tilt, vertically oval or tilted optic disc, and varying power in different meridians. The underlying causes of astigmatism can be attributed to corneal, lenticular, or retinal factors. Regular astigmatism can further be classified into "with the rule" astigmatism, "against the rule" astigmatism, oblique astigmatism, and bi-oblique astigmatism. The principles of Sturm's conoid elucidate the optics of regular astigmatism. In regular astigmatism case...