Slit lamp having replaceable objective lens unit for observation of cornea

Slit lamp including a slit illumination system for projecting a slit luminous flux to a patient's eye, a body provided with a mount, objective lens means adapted to be mounted through said mount on said body so that it can be easily replaced, a binocular microscopic system including a pair of optical paths for observing an illuminated portion of the patient's eye through said objective lens means, a pair of variable power lenses for varying the magnification of the image observed, said pair of variable power lenses being placed between said objective lens and said observing optical paths, a photographing optical system for taking photographs of said illuminated portion of the patient's eye, said photographing system having at least one optical path which is at least partially in common with said binocular optical system, and an alternative lens means for observing the ocular anterior of the patient's eye in high magnification, said alternative lens means being replaceably mountable through said mount on said body in lieu of said objective lens means, said alternative lens means including alternative objective lens means for focusing a beam of light at an image point, relay lens means for relaying said beam of light from said image point and optical means for directing the beam of light to one of the variable power lenses in the binocular microscopic system.