Optical sectioning of the cornea with a new confocal in vivo slit-scanning videomicroscope

The purpose of this article is to introduce a newly developed confocal in vivo slit-scanning microscope for continuous recording and real-time imaging of the various corneal subsegments of the patient's eye with high microscopical resolution and adequate contrast.

One-dimensional confocal slit-scanning videomicroscopy of the human cornea was performed with an instrument mainly consisting of a scanning module, an image-intensifier video camera, a video monitor, and a synchronization unit for matching optical scan and video cycle with respect to frequency and phase. Light intensity or fluorescence intensity profiles through the cornea could be obtained by microphotometric recording of part of the imaging light. An immersion contact technique using an isotonic tear replacement liquid with thixotropic properties avoids any mechanical contact between the front lens of the microscope objective and the corneal surface.

In normal human eyes, the corneal micromorphology could be made visible with satisfactory lateral and axial resolution and with good contrast. The separately focussed sections of the cornea showed the endothelial cells, the superficial, intermediary, and basal cells of the epithelium, as well as stromal keratocytes and nerves. Even in eyes with significant corneal opacities resulting from corneal edema, the endothelial pathology could be imaged with sufficient contrast.

The in vivo slit-scanning videomicroscopy offers real-time noninvasive and noncontact serial imaging of corneal subsegments with resolution and imaging contrast. Thus, an important step toward using confocal scanning microscopy for corneal diagnosis seems to be done.