(Science: ophthalmology) That refractive condition of the eye in which the rays of light are all brought accurately and without undue effort to a focus upon the retina; opposed to hypermetropia, myopia, an astigmatism.
For an example, read about emmetropia on pupilEyes.com
Origin: NL, fr. Gr. in measure, proportioned, suitable (in – measure) -, eye.