A Comparative Study of Clinical vs. Digital Exophthalmometry Measurement Methods

Abstract

Background. A number of orbital diseases may be evaluated based on the degree of exophthalmos, but there is still no gold standard method for the measurement of this parameter. In this study we compare two exophthalmometry measurement methods (digital photography and clinical) with regard to reproducibility and the level of correlation and agreement with measurements obtained with Computerized Tomography (CT) measurements. Methods. Seventeen patients with bilateral proptosis and 15 patients with normal orbits diseases were enrolled. Patients underwent orbital CT, Hertel exophthalmometry (HE) and standardized frontal and side facial photographs by a single trained photographer. Exophthalmometry measurements with HE, the digital photographs and axial CT scans were obtained twice by the same examiner and once by another examiner. Pearson correlation coefficient (PCC) was used to assess correlations between methods. Validity between methods was assessed by mean differences, interintraclass correlation coefficients (ICC’s), and Bland–Altman plots. Results. Mean values were significantly higher in the proptosis group (34 orbits) than in the normal group (30 orbits), regardless of the method. Within each group, mean digital exophthalmometry measurements (24.32 ± 5.17 mm and 18.62 ± 3.87 mm) were significantly greater than HE measurements (20.87 ± 2.53 mm and 17.52 ± 2.67 mm) with broader range of standard deviation. Inter-/intraclass correlation coefficients were 0.95/0.93 for clinical, 0.92/0.74 for digital, and 0.91/0.95 for CT measurements. Correlation coefficients between HE and CT scan measurements in both groups of subjects (r = 0.84 and r = 0.91, p<0.05) were greater than those between digital and CT scan measurements (r = 0.61 and r = 0.75, p<0.05). On the Bland–Altman plots, HE showed better agreement to CT measurements compared to the digital photograph method in both groups studied. Conclusions. Although photographic digital exophthalmometry showed strong correlation and agreement with CT scan measurements, it still performs worse than and is not as accurate as clinical Hertel exophthalmometry. This trail is registered with NCT01999790.

A novel method of measuring proptosis with computed tomography

“…Proptosis is a significant way of diagnosing some orbital diseases and evaluating their severity and surgical indications. As mentioned above, the HE method of measuring proptosis is still the most common method used in clinic due to the popularization of equipment, simplicity of use, and being radiation-free, but the HE method has individual difference and poor repeatability, reducing the accuracy and credibility of the value (13).…”

“…However, professional software often means high cost. Digital photography is a simple and non-invasive alternative method that has been used to assess proptosis; however, a study has demonstrated that compared to clinical HE exophthalmometry, this method has greater variance and lower correlation with the radiological tool (13). Conversely, many different methods have been applied to evaluate the radiology method based on 3D CT images, and almost all studies have arrived at a similar conclusion: that the radiology method is accurate and reproducible to measure proptosis and exhibited a high correlation with the HE method.…”

A new radiological measurement method used to evaluate the modified transconjunctival orbital fat decompression surgery

“…In recent years of research, some scholars measured the eyeball protrusion of TAO patients on the images obtained by CT scan, and they determined the most forward measurement position of the eyeballs by the the thickest position of the lens [ 9 , 10 ]. For TAO patients without myopathy, the CT slice of the thickest lens corresponds to the apex of the cornea, which is the most protruding position of the eyeball.…”

Evaluation of Proptosis: A Primer

“…Errors in measurement are caused by thickness of subcutaneous tissue over the bone, facial asymmetry, parallax and examiner skills. 6,31 Apart from Hertel's exophthalmometer, a simple plastic scale at the lateral orbital margin, or a Luedde exophthalmometer, can be used. The latter is a thick plastic ruler with a notch to fit in the lateral orbital margin and markings in millimetres on both sides of the scale to avoid parallax.…”