The ornamental design for a monocularopticalsystem for refractive error measurements, as shown and described.
FIG. 1 is a top and side perspective view of a monocular optical system for refractive error measurements showing a new design; the dotted lines showing a strap and smart phone illustrate environmental conditions only and form no part of the claimed design; the broken circular lines illustrate environmental conditions only and form no part of the claimed design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top view thereof; the alignment rectangle drawn in dotted lines illustrates environmental conditions only and forms no part of the claimed design; the broken circular lines illustrate environmental conditions only and form no part of the claimed design;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a bottom front perspective view thereof.
The dotted lines depicting the word “EyeQue” of FIGS. 1, 2, 3 and 4 illustrate environmental conditions only and form no part of the claimed design.