What's the difference between dioptra and dioptry?

Dioptra

Definition:

(n.) An optical instrument, invented by Hipparchus, for taking altitudes, leveling, etc.

Example Sentences:

Definition:

Example Sentences:

(1) Oculomotor visual input of the postural system can be modified with a small powerful prism from 1 to 4 dioptries.
(2) Medium astigmatism was 3 dioptries, always regular.
(3) 28 patients with high myopia (over-10 dioptries) were implanted in anterior chamber with a myopic IOL.
(4) The accommodation diminished from 6 to 2 dioptries in patients, and from 8 to 5 dioptries in controls.
(5) It's necessary to take a color slide of the optic nerve head (Kodachrome 64 asa, angle 45 degrees) and measure parameters on the patient (length in mm of the flashed slit on the optic nerve head with the slotted light and Goldmann lens, the measurement in dioptries of the ametropia and the radius in mm of the anterior surface of the cornea).