What does emmetrope mean?
An emmetrope is a person whose eyes exhibit emmetropia, the ideal state of ocular refraction in which incoming light rays come to a sharp focus directly on the retina without any corrective lens. In practical terms, an emmetrope sees distant objects clearly unaided — no spectacles or contact lenses required. The term belongs chiefly to the professional vocabularies of optometry, ophthalmology, and vision research, where it serves as the neutral counterpart to 'ametrope', the umbrella term for someone with a refractive error such as myopia, hyperopia, or astigmatism. Clinicians and researchers value the word because it allows precise description of study participants and patients: a trial of new lenses, for instance, might compare performance in corrected ametropes against that of true emmetropes. Though rare outside clinical settings, the word captures a genuinely enviable condition — many people wear glasses precisely because they are not emmetropes.
nounA person whose eyes are in a normal state of refraction, so that parallel light rays focus precisely on the retina without the need for corrective lenses.
- A person with normal ocular refraction, requiring no corrective lenses for distance vision.
"As an emmetrope, she had never needed glasses and found her friends' prescriptions baffling."
"The optometrist confirmed that the child was an emmetrope with perfect visual acuity."
"Studies comparing contrast sensitivity often recruit both ametropes corrected by lenses and untreated emmetropes."
Standard English plural, used when referring to multiple individuals with normal refraction, as in research cohorts.
"The study enrolled fifty emmetropes as a control group."
Roughly a third of people are born emmetropes — the lucky ones who never need to hunt for their glasses in the morning.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of emmetrope
The word derives from Greek roots: 'emmetros' meaning 'in measure' or 'well-proportioned' (from 'en' meaning 'in' plus 'metron' meaning 'measure') combined with 'ops' meaning 'eye'. It entered scientific usage through the nineteenth-century term 'emmetropia', coined to describe the properly measured, normally focused eye. Cognates built on the same Greek elements include 'emmetropia' itself and its adjectival form 'emmetropic'.
Related word forms
How emmetrope is actually used
Strictly technical vocabulary, used almost exclusively in optometry, ophthalmology, and vision science; it would sound out of place in everyday conversation, where 'someone who doesn't need glasses' is the natural phrasing.
Easily confused with emmetrope
An ametrope has a refractive error such as myopia or hyperopia, whereas an emmetrope has normally focusing eyes.