Evaluation of the effect of strabi̇smus surgery on retinal vascular density

Aim: The evaluation of the impact of horizontal muscle surgery on retinal vessel density. Materials and Methods: In the study, 30 patients who underwent surgery for strabismus in one eye at the Department of Ophthalmology, Dicle University Medical School, were included. The eye that underwent surgery and the healthy eye of 30 matched controls were analyzed. Detailed eye examinations were performed before and after the surgery. Best-corrected visual acuity was measured, and Hirschberg test and prism cover test were conducted. Optical coherence tomography (OCT) and OCT angiography (OCTA) scans were performed for all patients included in the study. Results: Twenty-three patients (74.2%) underwent surgery for exotropia, and 8 patients (25.8%) underwent surgery for esotropia. The average age of the patients was 16.6 ± 5.1 years. The average angle of deviation was measured at 25.9 ± 8.2 prism diopters, and the average follow-up period was 3.6 ± 1.9 months. No significant differences were found between the operated eye and the control eye in terms of YKP VD, DKP VD, and FAZ in all surgical groups. Additionally, no correlation was found between YKP VD and DKP VD values with age, angle of deviation, follow-up period, or the amount of horizontal muscle recession and resection. A significant positive correlation was observed between FAZ area and MR resection amount (p=0.018). FAZ PERİM XT values were similar between the operated and control eyes in horizontal surgery groups. In the ET surgical group, FAZ PERİM was higher in the operated eye compared to the healthy eye (p=0.023). A strong positive correlation was found between FAZ PERİM and MR resection amount (p=0.01). In XT surgery cases, parafoveal VD, parafoveal inferior VD, parafoveal nasal VD, and parafoveal superior hemi VD values were lower in the late period compared to control eyes (p=0.022, p=0.044, p=0.019, p=0.015, respectively). Correlation and regression analyses showed that this decrease was not affected by age, follow-up period, angle of deviation, or the amount of horizontal muscle recession/resection. In the ET surgical group, fovea VD value was lower, while parafoveal inferior VD and parafoveal nasal VD values were higher in the late period (p=0.008, p=0.039, p=0.039, respectively). Correlation and regression analyses indicated that these changes were not influenced by age, follow-up period, angle of deviation, or the amount of horizontal muscle recession/resection. In the horizontal surgery group, only the superior hemi retinal thickness value decreased, while no changes were observed in other regions (p=0.046). In the XT and ET groups, no changes were detected in retinal thickness values in the late period. Conclusion: Changes in VD were observed between the operated and healthy eyes of patients who underwent strabismus surgery in the late period. However, these changes did not have an effect on retinal thickness in the late period. Further studies with larger sample sizes are needed to fully explain the reasons for the changes in vascular density. Keywords: Strabismus surgery, optical coherence tomography angiography, vascular density, retinal thickness, one eye