On-line 3-dimensional confocal imaging in vivo

PURPOSE. In vivo confocal microscopy through focusing (CMTF) can provide a 3-D stack of high-resolution corneal images and allows objective measuremen ts of corneal sublayer thickness and backscattering. However, current syste ms require time-consuming off-line image processing and analysis on multipl e software platforms. Furthermore, there is a trade off between the CMTF sp eed and measurement precision. The purpose of this study was to develop a n ovel on-line system for in vivo corneal imaging and analysis that overcomes these limitations. METHODS. A tandem scanning confocal microscope (TSCM) was used for corneal imaging. The TSCM video camera was interfaced directly to a PC image acquis ition board to implement real-time digitization. Software was developed to allow in vivo 2-D imaging, CMTF image acquisition, interactive 3-D reconstr uction, and analysis of CMTF data to be performed on line in a single user- friendly environment. A procedure was also incorporated to separate the odd /even video fields, thereby doubling the CMTF sampling rate and theoretical ly improving the precision of CMTF thickness measurements by a factor of tw o. RESULTS. In vivo corneal examinations of a normal human and a photorefracti ve keratectomy patient are presented to demonstrate the capabilities of the new system. Improvements in the convenience, speed, and functionality of i n vivo CMTF image acquisition, display, and analysis are demonstrated. CONCLUSIONS. This is the first full-featured software package designed for in vivo TSCM imaging of the cornea, which performs both 2-D and 3-D image a cquisition, display, and processing as well as CMTF analysis. The use of a PC platform and incorporation of easy to use, on line, and interactive feat ures should help to improve the clinical utility of this technology.