What does perimetry mean?
Perimetry is the measurement of the boundary or extent of an area, most commonly the range of a person's visual field. In an ophthalmological or neurological setting, it is used to map how much a patient can see to the side, above, and below the point of direct focus, helping identify conditions such as glaucoma or visual-field loss. The word can also have a general mathematical meaning referring to the measurement of a surface's perimeter. Its principal association, however, is with a structured visual-field test. Perimetry is therefore useful both as a precise medical term and as a reminder that the limits of what we see can be measured. The term comes from Greek roots meaning “around” and “measure,” reflecting the practice of determining the extent around a particular area.
The measurement or mapping of the extent of a person's visual field, especially peripheral vision.
"Perimetry can help detect the gradual loss of peripheral vision associated with glaucoma."
This is the standard modern medical sense and is used especially in ophthalmology and neurology.
The measurement of the boundary or extent of a surface, area, or figure.
"The architect used perimetry to calculate the outline of the irregular plot."
This is a general and relatively uncommon sense outside technical or mathematical contexts.
The plural is used when referring to separate measurements or testing procedures.
"The results of the two perimetries were compared to track changes in her vision."
Perimetry maps the unseen edges of vision, showing what a person can see beyond the point where they are directly looking.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of perimetry
Perimetry was formed in the 19th century from Greek peri-, meaning “around,” and the related measuring root found in metron, “measure.” The word initially referred broadly to measurement around an area or boundary. Its later and dominant medical sense, the measurement of the field of vision, developed through the systematic study of visual-field extent. It is closely related in formation to perimeter, a word that also denotes an outer boundary.
How perimetry is actually used
In medicine, perimetry is usually understood as visual-field testing and is commonly used in ophthalmology and neurology. The more general geometric sense is much less common.
Easily confused with perimetry
Perimetry is the process or measurement of a boundary, especially the extent of the visual field, whereas a perimeter is the boundary itself.