Provide a valuable resource to your clients or customers by linking to this resource page. Just place the following link on your website.
An eye chart is an essential diagnostic tool used by eye doctors and medical professionals to measure visual acuity (the sharpness of vision). The chart typically consists of rows of standardized letters or symbols that decrease in size towards the bottom.
read more about eye chart ...The purpose of the measurement is to quantify the sharpness of a patient's sight. The resulting fraction (e.g., 20/20) means the patient can see at 20 feet what a person with normal vision can see at 20 feet. A lower acuity (e.g., 20/40) means the patient must stand at 20 feet to see what a normal person can see at 40 feet.
The most common types are the Snellen chart (using large block letters), and the ETDRS chart (the standardized chart used in clinical trials, featuring equal spacing and a geometric progression in size). Pediatricians often use charts with pictures or symbols (Allen figures) for pre-literate children.
The test is performed by having the patient stand a specified distance (usually 20 feet) from the chart. The patient covers one eye and reads the smallest line of letters or symbols they can clearly see. The test is repeated for the other eye and then both eyes together.
Visual acuity is a necessary measurement because it is the standard metric used to track eye health and diagnose conditions. A drop in visual acuity can signal the onset of cataracts, macular degeneration, or changes in refractive error.
The visual acuity measured on the chart determines the strength of the contact lens prescription. The doctor refines the power until the patient achieves the clearest possible vision on the smallest line they can read.
No, 20/20 is considered normal vision. Some people can see better (e.g., 20/15).
No, there are specialized hand-held charts used to measure near vision acuity.
No, color blindness is tested using specialized Ishihara dot plates, not the standard acuity chart.
If you cannot read the "Big E" (20/400) on the chart with your glasses on, you may be classified as "Legally Blind." However, the eye chart only measures central clarity. If your side vision is fading but you can still read the chart, you may have advanced Glaucoma that requires medical imaging.
AAO. Visual Acuity and Eye Charts (aao.org). 2024.
AOA. Comprehensive Eye Exams (aoa.org). 2024.
National Eye Institute. Vision Testing (nei.nih.gov). 2024.
Cleveland Clinic. Eye Exam Guide (clevelandclinic.org). 2024.