How do you detect the Astigmatism by using snellen chart?

To detect astigmatism using a Snellen chart, an eye care professional will ask the patient to read letters from the chart at a specified distance. If the patient has astigmatism, they may experience difficulty seeing letters clearly in one orientation (horizontal or vertical) but not the other. The practitioner may also use a modified version of the chart, which includes lines of varying orientations, to assess clarity and determine any discrepancies in vision that suggest astigmatism. Additionally, the patient’s responses can help gauge the severity and axis of the astigmatism.