Abstract: Apparatus for use with an operating microscope employed in observing the cornea of the human eye, for example in connection with cornea transplant operations. A plexiglass tube surrounds the objective of the microscope and is fed with light from a suitable source, so that an image of the circular illuminated lower end of the plexiglass tube is reflected by the cornea of the patient back into the microscope and is observed by the person using the microscope. The character and extent of distortion of the reflected image is an indication of the corneal astigmatism. The eyepiece of the microscope is provided with a reticle in connection with which the reflected image is observed. In one form of the invention, the recticle has diametrical crossed lines and concentric circular lines.

Abstract: A photocoagulator using a gas discharge lamp and a mirror for forming a double image of the luminous plasma region of the lamp in a photocoagulation area adjusted for size by interchangeable field stops is improved for easier adjustability when field stop sizes are changed. A manually operable screw ring moves the lamp axially relative to the mirror to adjust the separation of one image from the other relative to the size of the field stop, and the side of the field stop facing toward the coagulation area is illuminated for brightening the environment of the coagulation area for easier observation.

Abstract: For automatic focusing of a stereoscopic microscope a focusing beam of rays, preferably in the infrared range of wave length, is generated by a pulse light source, and focused on the object to be observed in the form of a small luminous area which is superimposed on the observation rays. The rays reflected back by the object along the divided paths of the observation rays are deflected from those paths and directed to impinge on separate photoelectric detectors which convert axial shifts of the object plane with respect to the microscope into a directionally dependent electric signal which controls a focusing motor to move the microscope to compensate for such shifts. A switch is provided to permit manual adjustment of focus preparatory to automatic adjustment.