n. The measurement of the range of vision.n. The measurement of the visual powers in general (including the acuteness of the perception of form, of light, and of colors — eidoptometry, photoptometry, and chromatoptometry respectively), of the extent of the visual field (perioptometry), of the accommodative and refractive states of the eye (dioptometry), and of the position and movements of the eyeball. (ophthalmostatometry and ophthalmotropometry).