Can you read these sentences at 1 foot distance?
Nearly half of all blindness can be prevented.
Everyone should have periodic eye examinations.
Nearly half of all blindness can be prevented.
Everyone should have periodic eye examinations.
Nearly half of all blindness can be prevented.
Everyone should have periodic eye examinations.
Nearly half of all blindness can be prevented.
Everyone should have periodic eye examinations.
Have your eyes checked, if you can't read first two sentences or find out the gap
in the ring.
The first one of these special eye charts is the astigmatic mirror that is used
to diagnose and reduce astigmatism. Here is the chart (credit: www.i-see.org):
If an astigmatic looks at the lines near the center, some of the lines look darker
in some directions than others.
A typical astigmatic will see the lines near the horizontal clearer and darker than
the vertical ones. Horizontal lines may look spaced wider than the vertical ones,
too!
Also the inner circle may not look quite round in shape.