Dramatic Decrease in Ocular Deviation 1 Day before Surgery in Patients with Intermittent Exotropia

PURPOSE: To evaluate the clinical characteristics of patients with intermittent exotropia who exhibited a dramatic decrease in ocular deviation 1 day before surgery. METHODS: This study retrospectively enrolled patients with intermittent exotropia who underwent surgery between December 2013 and December 2019. Those who exhibited a decrease in ocular alignment ≥10 prism diopters (PD) at the last examination (1 day before surgery) compared with the largest previous angle of deviation were included. A monocular occlusion test was performed to re-confirm the largest angle of ocular deviation. RESULTS: Among 547 patients with intermittent exotropia, 10 (six females; mean age, 8.6 years) exhibited a dramatic decrease in ocular deviation before impending surgery. The mean largest angle of deviation was 31.0 PD (range, 20 to 50 PD) at distance and 34.5 PD (range, 20 to 55 PD) at near. The mean control scores using the LACTOSE (Look and Cover then Ten Seconds of Observation Scale for Exotropia) scoring system were 2.5 at distance, 1.8 at near, and 4.3 when combined. Mean ocular deviation prior to the impending surgery decreased to 7.4 PD (range, 0 to 10 PD) at distance and 6.2 PD (range, -10 to 10 PD) at near. The largest angle of ocular deviation was re-confirmed using the monocular occlusion test in all patients. All patients underwent surgery as planned, and none exhibited postoperative overcorrection. CONCLUSIONS: A relatively small number of patients with intermittent exotropia exhibited a dramatic decrease in ocular alignment 1 day before surgery but demonstrated a relatively better level of control. The monocular occlusion test was helpful in re-confirming the largest angle of ocular deviation.