The forced duction test
was free of restriction, and a smooth porous polyethylene implant was used to repair the orbital floor defect.
If a preoperative forced duction test was positive, antagonist muscle weakening surgery was performed, and then augmented partial rectus muscle transposition (APRMT) + partial horizontal rectus recession-resection was performed 2 months later.
A forced duction test was performed before surgery to determine if the antagonist muscles of the paralytic muscle had any restrictive factors such as contracture.
Patients 1 and 2 had positive results in the forced duction test and they underwent weakening surgery of the antagonistic muscles first and combined APRMT and partial horizontal rectus recession-resection 2 months later.
Diplopia occurs due to many factors which can be differentiated clinically or by forced duction test.
Mechanical entrapment of the orbital content most commonly the inferior rectus muscle followed by the inferior oblique muscle causes diplopia in up gaze and down gaze and the forced duction test in this case is positive.
Strabismus surgery was performed according to the results of forced duction test (FDT).
The forced duction test was positive for inferior rectus (IR) of the involved eye in 20 of the 36 eyes (55.55%).
Forced duction test
preoperatively showed restriction in all directions and maximum in abduction.
Dutton (1991) mentioned that a positive forced duction test
may be misleading as it does not always correlate with entrapment.8 Indication for early operation is symptomatic diplopia with posi- tive forced duction test
and CT evidence of entrapment of orbital fat or septae with no improvement over one to two weeks.
In the absence of IR restriction, (forced duction test
negative) surgical treatment comprises of the KNAPP PROCEDURE 8, 9.
High myopia should be considered in the differential diagnosis such as the 6th nerve palsy excluded by Positive forced duction test
, Thyroid eye disease excluded by Normal muscles on CT, Myasthenia Gravis excluded by a Normal tensilon test.