Evaluation of Strabocheck® as an objective measurement method of comitant horizontal strabismus in children undergoing surgery

The gold standard of angle measurement is the prism alternating cover test (PCT). This method requires cooperation from the child, experience, and presents a significant inter-observer variability. Strabocheck®(SK) is a new simple tool for objective and semi-automated angle measurement. Our purpose is to evaluate Strabocheck® in children undergoing surgery for comitant horizontal strabismus. The study population was divided into 3 groups: infantile esotropia, partially accommodative esotropia and intermittent exotropia. The primary endpoint was the agreement between Strabocheck®and the PCT. A total of 44 children were included prospectively. The correlation between the angle measured by the PCT and the angle measured by SK was strong (R = 0.87). The mean absolute difference in the angle measured by the two methods was Δ = 11.9+/- 9.8 diopters. The Bland-Altman plot shows a 95% interval limit between -30.0 [-34.4; -25.6] and 31.0 [26.7; 35.4] diopters. SK is an interesting tool to evaluate the angle of strabismus in children. However, the residual discordance between PCT and SK leads us to question the real value of the angle, which can only be approximated. A better clinical experience of this new tool in relation to the clinical condition and the PCT will allow to have a more accurate idea on the true angle and will probably help the surgeon to adapt this procedure.