Binocular Summation with qCSF: A Novel Method to Evaluate Binocular Function in Intermittent Exotropia after Strabismus Surgery

Abstract

Purpose : Strabismus surgery can potential improve functional vision and quality of life for Intermittent Exotropia (IXT) patients. We plan to evaluate changes of binocular summation (BiS) at different spatial frequencies using the qCSF method and quality of life as well as their relationships in IXT patients before and after surgery to demonstrate surgical benefits to binocularity.

Methods : From July 1, 2021 to May 31, 2022, 63 patients with IXT and 41 healthy individuals were enrolled in a case-control study conducted at Zhongshan Ophthalmic Center. 48 of the IXT patients were included in a prospective study after successful corrective surgery to compare pre- and post-operative measures of CSF metrics and HRQOL scores. The primary outcome was BiS, the difference between metrics of binocular CSF and monocular CSF of the better eye. The secondary outcome was health-related quality of life (HRQOL) scores measured with Intermittent Exotropia Questionnaire (IXTQ) and Adult Strabismus (AS-20) Questionnaire. All participants underwent these measurements and IXT patients repeated the tests 1 month before and 2 months after surgery.

Results : 63 patients with IXT(33 females and 30 males, median [IQR] age, 9.0 [7.0-21.0] years) had similar monocular CSF metrics (all P > 0.05) and lower BiS based on all CSF metrics compared with the normal controls (all P < 0.05). 48 patients were included in post-operative analysis. There were significant improvements in AULCSF BiS, Cut-off BiS, and BiS at 6.0 cpd, 12.0 cpd and 18.0 cpd (P = 0.012, 0.007, 0.030, 0.003 and 0.004, respectively), while there was no improvement in BiS at 1.0 cpd, 1.5 cpd and 3.0 cpd (P = 0.786, P = 0.257 and P = 0.106, respectively). In addition, better BiS was associated with better stereoacuity and fusion ability, parts of HRQOL improved significantly after surgery, and the improvement correlated with BiS based on CSF Cut-off in children.

Conclusions : Using qCSF and strabismus questionnaires, this study provides a more comprehensive and detailed description of binocular visual function before and after surgery for IXT patients. qCSF provides a novel method for characterizing binocular function and prognosis in patients with IXT.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.