GLOSSARY OF TERMS

20/20 vision
20/20 vision, which represents normal visual acuity using the standard "E" letter chart, means that a person is able to identify a line of small sized letters at a distance of 20 feet.

Amblyopia
Commonly called lazy eye, amblyopia refers to a reduction or dimness of vision that occurs with no apparent pathology.

Age Related Macular Degeneration (ARM)
See Macular Degeneration.

Cataract
Cloudiness or opacity in the eye's lens or capsule.

Channel Model
The Channel Model equates visual cells to filters, or channels, that pass a certain range of information to the human visual system for processing.

Contrast Sensitivity
Refers to the ability of the visual system to distinguish between an object and its background.

Contrast Sensitivity Testing
Refers to a testing methodology that involves the measurement and analysis of the human visual system's ability to detect variances in the size and contrast of objects. Contrast sensitivity testing is a qualitative test, that is, it tests the functional vision, or how well individuals see everyday visual objects or scenes.

E-chart (also known as 20/20 letter chart)
A standard visual acuity tool used in testing the optics of the eye by measuring how well the eye is able to focus an image at a specific distance. Also known as the Snellen eye chart, the E-chart uses black letters on a white chart background. The E-chart test measures the quantity of an individual's vision and scoring is based on the distance at which an individual can accurately identify the tiniest set of black letters (e.g., 20/20 vision). Also see Snellen eye chart.

Functional Vision
Refers to the interaction of visual perception and the environment, or how well individuals see in their everyday lives (e.g., while driving or at work and play).

Glaucoma
An eye disease characterized by changes in the optic nerve, head and visual field. If left untreated, it may cause further damage to the optic nerve and result in permanent vision loss.

Human Factors
An area of scholarly study and research that deals with functional vision, or the interaction of visual perception and the environment. Human factors experts focus on determining the functional significance of refractive error or eye disease on a normally healthy visual system.

Macular Degeneration - Age Related (ARM)
Refers to the degeneration of the central area of the retina of the eye leading to a loss of central vision.

Ophthalmology
A science that deals with ocular diseases. An ophthalmologist is a medical doctor or eye surgeon who specializes in the treatment of eye diseases and disorders.

Optometrist
A doctor of optometry is a primary eye care practitioner who evaluates all aspects of a patient's vision including the diagnosis, management and treatment of refractive errors and eye diseases.

Sine Wave Gratings
Sine wave gratings are special test patterns for contrast sensitivity testing. Sine-wave grating contrast sensitivity testing uses varying sizes and contrasts of gray bars set up in circular patterns to test an individual's ability to detect different gratings to identify the individual's visual contrast threshold.

Snellen eye chart (also E-chart)
Hermann Snellen, a Dutch doctor, invented the Snellen eye chart in 1862. The Snellen eye chart tests an individual's visual acuity. Scoring is based on the distance at which an individual can correctly identify a tiny set of black letters on a white background. An average normal vision score (20/20) is based on correctly identifying the smallest set of black letters at a viewing distance of 20 feet.

Visual Forensics
Visual forensics deals with the use of functional vision as a standard for the analysis of legal issues and visually based demonstrative evidence.

Vision Science
A field of study that deals with the mechanisms of the optics and retina/brain system which transform an image received by the eye into neural code for visual system processing. A vision scientist defines, measures and assesses these mechanisms regarding visual perception and functional vision performance.

Visual Acuity
Visual acuity refers to the measurement of the power of the eye and is a quantitative measure of the eye's ability to see an in-focus image at a certain distance. It is usually determined by having an individual read letters of various sizes at a standard distance from a chart.

 

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