Impaired vision and blindness are common. About 3.4 million people in the US are blind or visually impaired. Vision is usually measured by visual acuity charts, and normal vision is expressed as 20/20 ...

The most common types of color blindness, or color vision deficiency, are genetic. However, other types may develop due to injuries, eye diseases, health problems, and side effects of treatment.

Most individuals with color vision deficiency have had it since birth. However, people can develop it later in life. If it develops due to a health problem, color blindness can worsen over time. Color ...