Clinical measurements of normative subjective cyclotorsion and cyclofusion in a healthy adult population

Purpose To investigate normative subjective cyclotorsion values and cyclofusion ranges in a healthy adult population. Methods A cross-sectional investigation was performed in 120 healthy, non-strabismic adults, 60 men and 60 women in the age range of 18-69 years. All subjects were assessed for cyclotorsion using the synoptophore and the single Maddox rod (SMR) methods. Cyclofusion was investigated with the synoptophore in 60 of the subjects. Results All age groups showed low values of subjective torsion, mainly excyclotorsion with mean values of -1 degree for both methods. Reference ranges of cyclotorsion were between -0.7 and -1.5 degrees for the SMR method and between -0.7 and -1.4 degrees using the synoptophore method. There were no significant differences between gender (p = 0.48), but the effect of age was significant for both methods (p = 0.026) demonstrating a slight increase in excyclotorsion with age. Cyclofusion showed a total mean amplitude of 16 degrees, the fusion range was +7 degrees of incyclotorsion to -9 degrees of excyclotorsion. Conclusions Subjective reference ranges for cyclotorsion and cyclofusion reveal that low values of torsion are to be expected upon clinical investigation in non-strabismic adult individuals. Values outside of the reference range may be indicators of possible binocular abnormalities or physiological variations. The cyclotorsional measurements and prevalence in this adult population group can be regarded as normative data in clinical settings.