Glossary

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Central Vision(also: Foveal Vision)

Central vision is the area of sharpest sight in the visual field, corresponding to the fovea at the centre of the retina. It is responsible for detailed tasks such as reading, recognizing faces, and distinguishing fine detail and colour. Loss of central vision, commonly caused…

Central Vision Loss(also: Central Field Loss, Central Scotoma)

Loss of vision in the central part of the visual field, typically caused by damage to the macula — the area of the retina responsible for sharp, detailed vision. People with central vision loss experience difficulty seeing fine details directly in front of them, often describing…

Diabetic Retinopathy(also: DR)

A complication of diabetes that damages the blood vessels of the retina, potentially causing vision loss ranging from mild blurriness to complete blindness. Diabetic retinopathy can produce scattered and varied patterns of vision loss across the visual field, making it distinct…

Glaucoma

A group of eye conditions that damage the optic nerve, typically associated with elevated intraocular pressure. Glaucoma is a leading cause of irreversible blindness worldwide. It usually causes gradual loss of peripheral vision first, which can progress to tunnel vision and…

Macular Degeneration(also: AMD, Age-Related Macular Degeneration, ARMD)

A progressive eye condition that damages the macula — the central part of the retina responsible for sharp, detailed vision — leading to loss of central vision while peripheral vision typically remains intact. Age-related macular degeneration is the leading cause of severe…

Macular Degeneration(also: AMD, Age-Related Macular Degeneration, ARMD)

A progressive eye condition affecting the macula — the central part of the retina responsible for sharp, detailed vision. It is the leading cause of severe vision loss in people over 50 in developed countries. Macular degeneration gradually destroys central vision while…

Nystagmus(also: Involuntary Eye Movement, Dancing Eyes)

A condition involving involuntary, repetitive, and rhythmic movements of the eyes, which can be horizontal, vertical, or rotary. Nystagmus can be congenital (present from birth) or acquired later in life due to neurological conditions, medications, or other causes. It often…

Optic Neuropathy(also: Optic Nerve Disease)

Damage to the optic nerve that can result in vision loss, including reduced visual acuity, impaired color vision, and visual field defects. Optic neuropathy can be caused by various conditions including glaucoma, inflammation, ischemia, trauma, or toxic exposure. The pattern and…

Preferred Retinal Locus(also: PRL, Preferred Retinal Location)

A specific area of the retina outside the damaged macula that a person with central vision loss adopts as their primary fixation point for viewing. When the central fovea is damaged (as in macular degeneration), individuals naturally or through training develop one or more PRLs…

Retinitis Pigmentosa(also: RP)

A group of inherited genetic disorders that cause progressive degeneration of the retina, typically beginning with loss of night vision and peripheral vision and potentially leading to tunnel vision or complete blindness. RP affects the rod photoreceptor cells first, then may…

Saccade(also: Saccadic Eye Movement)

A rapid, ballistic eye movement that shifts the point of fixation from one location to another. Saccades are essential for visual search, reading, and scanning the environment. In low-vision rehabilitation, training saccadic eye movements helps individuals develop efficient…

Scotoma(also: Blind Spot, Visual Field Defect)

An area of partial or complete loss of vision within the visual field, surrounded by areas of relatively normal or less affected vision. Scotomas can result from conditions such as macular degeneration (central scotoma), glaucoma (peripheral scotomas), or retinal damage. People…

Scotoma(also: Blind Spot, Visual Field Defect)

An area of partial or complete loss of vision within an otherwise normal visual field. Scotomas can be central (affecting the area of sharpest vision) or peripheral, and may be caused by conditions such as macular degeneration, glaucoma, optic neuritis, or retinal damage. In the…

Stargardt Disease(also: Stargardt Macular Dystrophy, Juvenile Macular Degeneration)

An inherited eye disease that causes progressive damage to the macula, leading to central vision loss typically beginning in childhood or adolescence. Stargardt disease is the most common form of inherited macular degeneration. It may also affect color vision. Unlike age-related…

Visual Acuity(also: VA, Sharpness of Vision)

A measure of the eye's ability to distinguish fine details and shapes at a given distance. Visual acuity is commonly expressed as a Snellen fraction (e.g., 20/20, 20/200) or in logMAR units used in clinical research. It is the primary metric for classifying levels of vision…

Visual Field(also: Field of Vision)

The total area visible to a person when their eyes are fixated on a central point, including both central and peripheral vision. Visual field can be measured in degrees and is assessed through perimetry testing. Various eye conditions affect the visual field differently:…

Zernike Polynomials(also: Zernike Coefficients, Zernike Modes)

A set of mathematical functions used to describe the shape of optical wavefronts, commonly employed in ophthalmology and optometry to characterise the optical aberrations of the human eye. Each Zernike polynomial represents a specific type of optical distortion — for example,…

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