Forced duction test is to find out

(Refer: AK Khurana Comprehensive Ophthalmology, 6th edition, pg no. 353 - 354) Forced duction testIt is performed to differentiate between the incomitant squint due to paralysis of extraocular muscle and that due to the mechanical restriction of the ocular movements.FDT is positive (resistance encountered during passive rotation) in cases of incomitant squint due to mechanical restriction and negative in cases of extraocular muscle palsy.