Vision Wellness Institute
Evidence-Based Eye Health Education
Evidence-Based Eye Health Education
A comprehensive guide to vision health terms and concepts.
Welcome to the Vision Wellness Institute's Vision Health Glossary. This resource provides clear, evidence-based definitions for common terms related to vision health, eye conditions, digital eye strain, and related topics. Our goal is to help you better understand vision health concepts and communicate more effectively with healthcare providers.
This glossary is regularly updated to reflect current scientific understanding and terminology. If you don't find a term you're looking for, please contact us with your suggestion.
The process by which the eye changes optical power to maintain a clear image (focus) as the distance of objects changes. This is primarily achieved by the lens changing its shape.
A common vision condition where the cornea or lens has an irregular shape, causing blurred or distorted vision. Astigmatism occurs when light focuses on multiple points in the eye rather than a single point.
Also known as eye strain, asthenopia is a condition characterized by nonspecific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and occasional double vision. Symptoms often occur after reading, computer work, or other close activities that involve intense use of the eyes.
High-energy visible light in the blue-violet spectrum (approximately 380-500 nanometers). Blue light is present in sunlight but is also emitted by digital screens, LED lighting, and fluorescent lighting. Some research suggests that prolonged exposure to blue light, especially in the evening, may affect sleep patterns and potentially contribute to digital eye strain.
Technology designed to reduce the amount of blue light reaching the eye. This can include special coatings on eyeglasses, screen filters, software settings that adjust color temperature, or specialized lenses. The effectiveness and necessity of blue light filtering for eye health remains a topic of ongoing research.
The frequency at which a person blinks, typically measured in blinks per minute. The normal blink rate is approximately 15-20 blinks per minute, but this rate often decreases significantly (to as few as 5-7 blinks per minute) during computer use or other digital device use, potentially contributing to dry eye symptoms.
A group of eye and vision-related problems that result from prolonged computer, tablet, e-reader, and cell phone use. Many individuals experience eye discomfort and vision problems when viewing digital screens for extended periods. The level of discomfort appears to increase with the amount of digital screen use.
The ability to distinguish between an object and its background based on differences in luminance (brightness). Good contrast sensitivity is important for many everyday tasks, including reading, driving, and recognizing faces. Digital eye strain can temporarily reduce contrast sensitivity.
The clear, dome-shaped surface that covers the front of the eye. The cornea is the eye's outermost lens that helps focus light as it enters the eye. It provides about 65-75% of the eye's focusing power.
A condition characterized by visual discomfort after prolonged use of digital devices such as computers, smartphones, and tablets. Symptoms include eye fatigue, dry eyes, blurred vision, headaches, and neck/shoulder pain. Contributing factors include blue light exposure, reduced blink rate, improper viewing distance, poor lighting, and uncorrected vision problems.
A unit of measurement that describes the optical power of a lens, equal to the reciprocal of the focal length in meters. It is commonly used in prescriptions for eyeglasses and contact lenses. Positive diopters indicate farsightedness (hyperopia), while negative diopters indicate nearsightedness (myopia).
A condition where the eyes don't produce enough tears or the tears evaporate too quickly. This can lead to discomfort, irritation, redness, and blurred vision. Digital device use can exacerbate dry eye symptoms due to reduced blink rate and increased tear evaporation.
The science of designing and arranging things people use so that the people and things interact most efficiently and safely. In the context of vision health, ergonomics involves optimizing factors such as screen position, lighting, seating, and work habits to reduce eye strain and related discomfort.
A sensation of tiredness or discomfort in or around the eyes, often associated with intensive use of the eyes for activities like reading, driving, or using digital devices. Symptoms may include soreness, burning, itching, dryness, blurred vision, and headache.
The rapid variation in the brightness of a light source or display. Some people are sensitive to the imperceptible flicker of certain types of lighting (such as fluorescent lights) or screens, which can contribute to eye strain, headaches, and visual discomfort.
Tiredness of the ciliary muscles that control the shape of the eye's lens for focusing. This can occur after prolonged near work, such as reading or using digital devices, and may result in temporary difficulty focusing, blurred vision, or discomfort.
Excessive brightness or reflection that causes visual discomfort or reduced visibility. Glare can come from direct light sources, reflections off screens or surfaces, or bright backgrounds. It can contribute to eye strain and reduced visual performance.
The portion of the visible light spectrum with the highest energy, which includes blue-violet light (approximately 380-500 nanometers). Some research suggests that prolonged exposure to HEV light may contribute to digital eye strain and potentially affect long-term eye health.
Also known as nearsightedness, myopia is a refractive error where close objects appear clear but distant objects appear blurry. It occurs when the eyeball is too long or the cornea is too curved, causing light to focus in front of the retina rather than directly on it.
A guideline for reducing digital eye strain: every 20 minutes, take a 20-second break to look at something 20 feet away. This practice helps relax the focusing muscles of the eyes and reduces the symptoms of digital eye strain.