[A new method for measuring exophthalmos. The slit lamp exophthalmometer].

We compared the most commonly used exophthalmometer according to Hertel (HE), which is criticized in the literature because of its low reliability, with the prototype of a new slitlamp exophthalmometer (SE). The apex of the eye and an index mark, which is in a fixed relation to the orbit, can be observed simultaneously, using a system of two mirrows. The advantages are a more accurate scale (up to 5/100 mm) and the independence of measurements. Exophthalmometry was performed in two experiments. First, we measured an artificial eye to determine the intra- and interobserver variation. The values of HE were 0.18 mm and 0.27 mm, respectively, those of SLE less than 0.08 mm. Second, we measured ten healthy volunteers to determine the interobserver variation. The value of SLE was significantly smaller (P < 0.01) than the value of HE. In conclusion, the SE is more reliable than the HE concerning the intra- and interobserver variation and can be recommended for research purposes as a useful alternative to the HE.