Some clinical characteristics of V-pattern exotropia and surgical outcome after bilateral recession of the inferior oblique muscle: a retrospective study of 22 consecutive patients and a comparison with V-pattern esotropia.

BACKGROUND AND PURPOSE: A V-pattern exotropia (XT) with bilateral overaction of the inferior obliques (IO) and/or underaction of the superior obliques (SO) is a common finding. The clinical characteristics of this condition in a large series are not available in the scientific literature. Also, data is lacking about the surgical outcome of graded bilateral IO recession. Lastly, a comparison of the pre- and postoperative findings of a V-pattern exotropia population with those of a V-pattern esotropia population is also lacking in the literature.

SUBJECTS AND METHODS: Twenty-two consecutive patients without complicating factors were fully evaluated and submitted to bilateral graded recessions of the IO; 19 were also operated for a horizontal binocular alignment imbalance.

RESULTS: Preoperative findings: The distribution of V patterns showed 77.2% in the range of 15 to 25 prism diopters (PD) and 22.8% in the range 26 to 35 PD. An overaction of the IO was present bilaterally in 86.4% of the patients and unilaterally in 4.5%. Bilateral underaction of the SO was observed in 4.5% and unilateral in 13.6%. Bilateral overaction of the SO was seen in 18.2% and unilateral in 31.8%. Elevation in adduction was observed bilaterally in 13.6% and unilaterally in 31.8%. A vertical deviation was seen in 50.0% and a marked tendency of it to vanish or diminish in the up- and down positions, as well as at near, was observed. After surgery, 72.7% had less than 15 PD of V pattern or less than 10 PD of A pattern; 36.4% had the V pattern fully corrected. Surgery eliminated a vertical imbalance in 72.7% of the patients, reduced in 9.1%, left unchanged in 9.1% and increased in 9.1% Of the 11 patients devoid of vertical deviation, 72.7% remained so and in 27.3% a vertical deviation was created. Binocularity: There was an improvement of the fusional status with surgery, (ascertained with the Worth Four Dot Test and the major amblyoscope measurement).

CONCLUSION: All cases were in the range of 15-35 PD preop'. Overaction of the IO was a prominent finding. Underaction of the SO was less prevalent as compared with a V-ET population. Overaction of the SO was observed bilaterally in 18.2% and unilaterally in 31.8%, a finding never detected in a V-ET population. A vertical imbalance was observed in one-half of the cases. A good outcome (collapse of the V pattern) was obtained with bilateral graded recession of the IO, This procedure is relatively safe concerning the vertical alignment.