Exophthalmometry: a comparative study of the Naugle and Hertel instruments

Exophthalmometry is frequently used as a tool in the evaluation of proptosis. The purpose of this study was to compare the clinical usefulness of the newly developed Naugle superior and inferior orbital rim-based exophthalmometer with that of the Hertel exophthalmometer, as well as to obtain normal values and analysis of possible race and sex differences. In the first part of this study, we measured 135 patients in a double-blind study in order to evaluate the repeatability of serial measurements using each instrument. Comfort was also evaluated in this series of patients. In the second part, a single observer measured 205 patients in order to obtain information for a multifaceted analysis. In the first part of the study, we found the Hertel measurement to be more variable in terms of coefficients of variation. We further found the Hertel base measurements to vary more between observers than those of the Naugle instrument. In the second part, we found that the mean values of globe position were not statistically different (mean Naugle, 17.23; mean Hertel, 18.61; p = 0.909). A significant difference was noted between black and white patients when using the Naugle instrument. A difference between white and black women was noted with the Hertel instrument. The results of this analysis strongly suggest that the values obtained from the Naugle exophthalmometer are more repeatable in serial measurements compared with the Hertel values. However, single measurements of globe position from all patients were statistically similar. We conclude that the Naugle instrument is comparable in accuracy to the Hertel instrument for measuring ocular position, as well as being more comfortable for the patient. The Naugle instrument has the advantage of measuring hyperophthalmos and hypoophthalmos with a vertical gradient scale.