To evaluate diagnostic the usefulness of blind spot mapping in measuring ocular torsion changes and to investigate the correlations of inferior oblique muscle overaction (IOOA) and excyclotorsion measurements using fundus photographs and blind spot mapping in patients with secondary IOOA.

Eleven patients (12 eyes; IOOA group) diagnosed with secondary IOOA were evaluated for ocular movement, fundus photograph and Humphrey standard automated perimetry, and 10 patients (20 eyes; control group) were subjected to the same tests. An ocular movement examination was performed to evaluate IOOA, and fundus photograph and Humphrey standard automated perimetry were used to measure the ocular torsion. Inferior oblique myectomy or recession was performed along with horizontal strabismus surgery, and preoperative and postoperative IOOA and ocular torsion measurements were compared between the groups.

In the IOOA group after surgery, the IOOA decreased from +2.42 ± 0.63 to +0.50 ± 0.52, the ocular torsion decreased from +14.15 ± 3.60° to +7.47 ± 1.65° ( p < 0.001) on fundus photographs, and from +12.19 ± 1.62° to +9.69 ± 1.75° ( p = 0.061) in Humphrey standard automated perimetry. The control group showed a mean ocular torsion of 7.44 ± 1.62° on fundus photographs and +7.24 ± 1.28° on Humphrey standard automated perimetry.

The usefulness of blind spot mapping when the ocular torsion was measured in IOOA patients was considered low, due to the weak correlation between IOOA and extorsion; preoperative and postoperative ocular torsion amount values were not significantly different.