1. A movable device for improved monocular centration of a fixation light attached to a surgical binocular microscope, said device comprising: a directionally movable light source within a ring-shaped casing, wherein the casing has an ophthalmologist-facing top side, and a patient-facing lower side, both of which are open or transparent to expose the light source within, wherein the casing creates a minimal footprint in line of vision of the ophthalmologist viewing a patient's eye (Z-axis), such that light is projected as a single focused beam of light on, or parallel to, the Z-axis by the light source from within the casing, simultaneously through both the upper and lower sides of the casing ring.