The subjectivity of objective evaluation of torsion on fundus photographs by practicing strabismologists

PURPOSE: To assess the variability of assessing the ocular torsion on fundus photographs among strabismus surgeons. METHODS: This was a prospective, noninterventional, clinical trial involving 16 trained and experienced squint surgeons participated in the study. Two videos were prepared of a total of 10 fundus pictures with or without lines for disc foveal angle. The first video had a 4 s viewing time for each fundus image. The second video had the disc foveal lines drawn and a similar 4 s viewing time for each image. The participants were asked to grade the torsion. The primary outcome measure was to assess the agreement between the raters for ocular torsion measurement. Difference in the response of observers from the standard response was the secondary outcome measure. RESULTS: A 4 s viewing time was given to mimic the exposure time in the clinic while assessing torsion in a patient. Large variability was found among the responses. The kappa test was done for comparing the agreement between various observers which ranged from slight to fair (<0.40). There was no difference in torsion grading in 30.6% and 26.3% responses in the first and second video from the standard response, respectively. When a limit of ±1 grade was taken as acceptable for the responses, 66.2% for the first and 68.7% for the second video respectively were similar to standard response. CONCLUSION: There is wide variability in assessing ocular torsion by fundus photography. The level of accuracy does increase with marking the line on photographs but still remains unreliable.