Eye strain, also known as asthenopia (from astheno- 'loss of strength' and -opia 'relating to the eyes'), is a common eye condition that manifests through non-specific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and occasional double vision.[1] Symptoms often occur after long-term use of computers, digital devices, reading, or other activities that involve extended visual tasks[2] which are broadly classified into external and internal symptom factors.[1] The experience of eye strain when reading in dim light has given rise to the common misconception that such an activity causes permanent eye damage.[3]
When concentrating on a visually intense task, such as continuously focusing on a book or computer monitor, the ciliary muscles and the extraocular muscles are strained. This causes discomfort, soreness, and/or pain in the eyeballs. Closing the eyes for ten minutes and relaxing the muscles of the face and neck at least once an hour usually relieves the problem.
A page or photograph which shows the same image twice, but slightly displaced–from a printing mishap, a camera moving during the shot, etc.–can cause eye strain due to the brain misinterpreting the image fault as diplopia and reacting by adjusting the sideways movements of the two eyeballs, in an attempt to fuse the two images into one.
Eye strain can also happen when viewing a blurry image (including images deliberately partly blurred for censorship), due to the ciliary muscle tightening in an attempt to focus the blurring out.
