Remember when you were a child and broke your arm and had to wear a heavy, hot plaster cast in the Summer? Your arm felt heavy and itchy, your muscles atrophied, you had to wear a plastic bag over your cast to shower, and, after a couple of weeks, the cotton padding inside stunk. The only good thing about it,...

Visual acuity (clearness of vision) usually is measured by an eye doctor using an eye chart. It measures the smallest letters that can be reliably identified by the patient at a specified distance. The traditional test requires the patient to look and report which letters they see.