The present invention relates to an auto-keratometer for automatically measuring an abnormal curving or astigmatic condition of the cornea, and more particularly it relates to improvements in a means for attaching a light source section therefor. 
Generally, in operations on the cornea, such as for cataract and corneal transplantation, to provide good eyesight after operation it is necessary to accurately control the corneal shape while measuring the corneal refraction or corneal astigmatic condition making allowance for a possible change in the corneal shape. 
Thus, it has been common practice to make automatic measurements of the corneal condition by installing a light source section having a built-in fluorescent lamp and stroboscopic lamp under an existing operating microscope, causing the light from said light source section to strike on the patient's eye, adjusting the vertical position of the microscope while observing the reflected image of the cornea with the eyepiece through the objective lens of the microscope and a beam splitter, and, upon completion of the alignment, indicating the result of the measurement on a display or printing it out. 
In the microscope described above, however, the vertical working distance below said microscope is as short as about 175 mm, accounting for the fact that installing a measuring light source such as a ring light source below the microscope has entailed the danger of causing trouble to surgical operation.  For this reason, there has been a desire for maximizing the working region below the microscope and above the cornea. 
In the case of an operation on the cornea, it has been necessary to install an assistant microscope to allow an assistant to observe the corneal condition in conjunction with the operator.  However, since the space below the microscope is limited, it has been sometimes impossible to attach the assistant microscope to the operating microscope.  Even if the assistant microscope can be attached thereto, the light source for the auto-keratometer forms an obstacle which limits the attachment of the assistant microscope to a position located laterally of the microscope.  As a result, the viewing angle of the objective lens of the assistant microscope relative to the cornea is increased, making it impossible to obtain the same field of vision as that for the operator, thus posing a problem in operation.