Purpose: To evaluate the subjective and objective cyclodeviational changes following different weakening procedures on superior and inferior oblique muscles.
Design: Comparative case series.
Materials and methods: In a prospective institution based study, 16 cases of A pattern horizontal strabismus having superior oblique overaction were randomized to superior oblique weakening procedures: either silicon expander or translational-recession. Similarly, 20 cases of V pattern horizontal strabismus with inferior oblique overaction were randomized for inferior oblique weakening procedures: either 10 mm Fink's recession or modified Elliot and Nankin's anteropositioning. Cyclodeviation was assessed subjectively with the synoptophore and objectively using the fundus photograph before surgery and 3 months postoperatively. Change in cyclodeviation was measured by subjective and objective methods. The index of surgical effect (ISE) was defined as the net torsional change postoperatively.
Results: The difference between the extorsional change induced by the two superior oblique procedures, silicone expander (-6 degrees ) and translational recession (-11.3 degrees), was statistically significant (P=0.001). Translational recession caused more extorsional change (ISE=296%) than silicone expander surgery (ISE=107%). The two inferior oblique weakening procedures, Fink's recession (+2.5 degrees) and modified Elliot and Nankin's anteropositioning (+4.7 degrees) produced equitable amount of intorsional shift with no statistical difference (P=0.93). Objective measurements were significantly more than the subjective measurements.
Conclusions: Different weakening procedures on oblique muscles produce different changes in cyclodeviation, which persists even up to 3 months. Subjective cyclodeviation is less than the objective measurements indicating partial compensation by sensorial adaptations.