Assertion: astigmatism | /r/CreatedBy | cornea
Facets:
Source sentences:
text: Astigmatism is a common refractive error caused by a cornea or lens that has an irregular shape, so light is refracted poorly onto the retina.
text: The amount of astigmatism caused by the cornea is measured in the clinic by a diagnostic instrument called a keratometer.
text: Astigmatism is a refractive error caused by a misshapen lens or cornea (the transparent covering over the iris, pupil, and lens) that prevents sufferers from seeing objects clearly from a distance or up close.