Microscope

Optical aids (e.g. loupes, OMs, surgical headlamps, fiberoptic handpiece lights) can improve resolution by many orders of magnitude.

For example, a common operative microscope can raise the resolving limit from 0.2 to 0.006 mm (6 μm), a dramatic improvement.
Stereopsis, or 3D perception, is critical to achieving precision surgery, and is an advantage over 2D endoscopes.
Several factors are important for increasing resolution without compromising ergonomics, eyestrain, head/neck fatigue

The separation of the reflected light into two beams within a microscope is what produces the stereoscopic effect that allows the clinician to see depth of field.

Magnify the interim image generated in the binocular tubes. Eyepiece selection not only determines the magnification, but also the size of the field of view.

The precise adjustment of the interpupillary distance (by adjusting the distance between binocular tubes holding the eyepieces) is the basic pre-requisite for the stereoscopic view of the operation area. Longer the focal length of binoculars, the greater the magnification and narrower the field of view. Many microscopes now include a beam splitter and a second set of teaching binoculars (non-stereoscopic as they split light from a single objective).

One cylinder, into which two Galilean telescope systems with various magnification factors are built.
The combination of the magnification changer with varying objective lenses and eyepiece yields an increasing magnification line when the control is adjusted.

Its focal length determines the working distance between the lens and the surgical field.
Magnification of approximately 4-40 × with an excellent illumination of the working area.
Focal Length:

The distance between the eye/lens and the patient
As the focal length decreases, the eyes must converge more closely around an axis to reduce the depth of field. → eye strain

The distance from the microscope objective lens to the point of focus of the optical system.
This value is fixed and is dependent on the chosen focal length of the objective lens

Most people who view two points closer than 0.2 mm will see only 1 point. Moving closer to an object increases resolution up to a point, but objects closer than 10-12 cm go out of focus.

The far-near range within which objects remains in focus without having to adjust working distance.
As magnification increases, depth of field decreases hence focusing on multiple objects at different depths with high magnification will require more changes in microscope position.
Also, the smaller the field of view, the shallower the depth of field

The width and height of the area visible through a lens system, which decreases with increasing magnification

As optimal illumination is necessary with high magnifications.
The light beams fall parallel onto the retinas of the observer so that no eye convergence is necessary and the demand on the lateral rectus muscles is minimal.
Surgical microscope uses coaxial fiber-optic illumination producing an adjustable, bright, uniformly illuminated, shadow-free, circular spot of light that is parallel to the optical viewing axis.
By increasing light levels, one can increase Resolving power: (the ability to distinguish two objects close to each other as separate and distinct).
Light intensity is determined by the inverse square law, which states that the amount of light received from a source is inversely proportional to the square of the distance

A = light fiber;

B = objective lens;

C = magnification changer;

D = teaching binoculars;

E = eyepiece;

F = main binoculars;

G = beam splitter