Technology

The Heidelberg Retina Tomograph (HRT) is a confocal scanning laser ophthalmoscope.  The instrument can be converted into a confocal corneal microscope using an optional add-on kit.  The kit is composed of an additional microscope lens which attaches to the standard lens.  Along with corneal analysis software, the HRT is able to image cells and cell layers within the cornea.

To create an image, a beam of light scans the cornea, creating a 384 x 384 point image in a 400 micron square at a magnification of 63X.  Because the system is confocal, it has two unique properties: the first is that the instrument can be focused at varying depths through the full thickness of the cornea, and second, stray light is blocked, enabling crisp, clear images not available from specular microscopes using white light sources.

Laser scanning with confocal imaging represents one of the most significant advances in ophthalmic imaging because it enables visualization deep within living tissue.   Confocal imaging has several advantages over white light photography including the ability to image within tissue at sequential depths, capturing sharply defined optical sections.  This is accomplished through a “pinhole” concept, which only allows light from the targeted focal plane to reach the sensor.