Slit lamp attachment

An attachment for a slit lamp that permits the operator to view the superimposition of an image of a patient's eye and a second image that may comprise a fluorescein angiogram or other photographic image of the patient's eye, or an image formed by a CRT or other display system. The slit lamp includes an objective for forming the first image directed along a first optical path, an eyepiece, being attachable to the objective such that the eyepiece is positioned along the first optical path. The attachment includes a body, a beamsplitter, and an image forming system. The body includes an attachment for attaching the body between the objective and viewing means, and also includes a passage through which the first image can pass along the first optical path to the eyepiece. The beamsplitter is mounted in the body, and positioned in the first optical path. The image forming system projects the second image onto the beamsplitter, such that a portion of the second image is reflected along the first optical path. The image forming system may include a zoom lens system for adjusting the size of the second image. The zoom lens system may comprise a pair of lenses and positioning means including an inner tube having a pair of helical slots and a pair of outer tubes having a pair of longitudinal slots. A beamsplitter positioning device is also provided for permitting the operator to precisely position the first and second images with respect to one another.