[Comparison of the measurement values of the laser tomography scanner and optic nerve head analyzer. A clinical study].

INTRODUCTION

With the Laser Tomographic Scanner (LTS) and the Optic Nerve Head Analyzer (ONHA) a quantifying investigation of the optic disc is possible. Both work with different principles: The LTS receives the information about the three dimensional structure with 32 transversal cuts, taken with the confocal principle, the ONHA with simultan stereopictures, taken from a different point of view.

PATIENTS AND METHODS

We examined 36 eyes (18 patients) with the LTS and the ONHA. The aim of the study is to examine, whether there are differences in the measurement values taken with the LTS and the ONHA investigating the same optic disc.

RESULTS

1. There are no significant differences in the measurement value of the area of the total disc and the horizontal and vertical diameter of the optic disc. 2. The measurement values of the area of the excavation and the quotient of the area of excavation to the area of the total disc are systematically greater in investigation with the LTS than in investigation with the ONHA. This is explained by the different definition of the boundary of the excavation. 3. There are significant differences in the measurement values of the volume of the excavation, the upper volume of the optic disc, and the maximum depth of the excavation. The measurement value of the volume of the excavation is systematically greater in investigation with the ONHA than in investigation with the LTS.

CONCLUSION

Measurement values of the parameters of the optic disc, which have the same definition in the LTS and the ONHA--such as the area of the total disc and the horizontal and vertical diameter of the optic disc--show no significant differences. Thus these parameters are comparable in the LTS and the ONHA.