Comparing slit lamp exophthalmometry with Hertel's exophthalmometry and computed tomography imaging in quantification of axial proptosis – A prospective analytical study

Aim: To compare the accuracy and precision of measurement of axial proptosis using novel slit-lamp exophthalmometry [SLE] and compare it with gold standard methods of Hertel's exophthalmometry and computed tomography (CT)-based methods. Methods: Patients with axial proptosis were assessed with novel slit-lamp exophthalmometry and compared with Hertel's exophthalmometry and CT measurements [3 CT methods]. Results: Correlational analysis between slit-lamp exophthalmometry and CT exophthalmometry demonstrated an ICC value of 0.912 indicates 'excellent' agreement, and 95% CI indicated non-significant change between the techniques. Intracorrelation coefficient examined strength of agreement. Values >0.75 showed 'excellent reliability'. Bland–Altman plots charted for comparison of SLE with Hertels', and CT exophthalmometry showed all differences to lie within the 2 SD boundaries suggestive of excellent agreement between the methods. Discussion and Conclusion: Advantages include stability to examiner and patients. Instrument errors are eliminated. Three CT methods and Hertel had statistically significant relationships with SLE. Exophthalmometry values are important for diagnoses, follow-up and treatment decision-making. Hence, a simple, objective examination method like SLE is needed to measure exophthalmos.