Evaluation of optical coherence tomography angiography data based on axial length in myopic patients

Objective: The aim is to comparatively assess the macular microvasculature in myopic patients based on axial lengths using Optical Coherence Tomography Angiography (OCTA) and to analyze the effects of increased axial length on macular microvascular circulation. Materials and Methods: The study included healthy volunteers with an axial length of 22 millimeters or more who visited the Ophthalmology Clinic at Karadeniz Technical University between August 2022 and April 2024 for a refractive error examination and had no other eye pathology. Participants were grouped by axial length: those with 22-24 millimeters (mm) (Group 1), 24-26 mm (Group 2), and 26 mm or more (Group 3). All participants underwent radial scanning macular SD-OCT and 6x6 mm OCT-Angiography imaging using the Solix OCT/OCTA device (Optovue Inc, Fremont, CA, USA). Superficial and deep capillary plexus vessel densities, FAZ (foveal avascular zone) area, and central foveal thickness in the 6x6 mm foveal and parafoveal regions were automatically calculated. Vessel density (%) measurements in the superficial and deep capillary networks were performed in macular areas corresponding to the 1mm and 3mm ETDRS grid model in the fovea and parafovea. The device automatically calculated central foveal thickness (CFT) as the average thickness within the central 1mm circular area. Additionally, vessel densities in the parafoveal and perifoveal regions in the superior, temporal, nasal, and inferior quadrants were automatically calculated by the device. Results: The study included 78 eyes from 49 participants (35 women and 14 men) with an average age of 35.5 years. Superficial Capillary Plexus (SCP) and Deep Capillary Plexus (DCP) vessel densities were significantly lower in Group 3 than in Groups 1 and 2, with no significant difference between Groups 1 and 2 (p=0.000, p=0.005, p=0.885, p=0.000, p=0.020, p=0.415, respectively). Parafoveal and perifoveal vessel densities in both DCP and SCP were significantly lower in Group 3 than in Groups 1 and 2 (p=0.016, p=0.001, p=0.024, p=0.002, respectively), with no significant difference between Groups 1 and 2 (p=0.113, p=0.477, p=0.346, p=0.840, respectively). Subfoveal choroidal thickness was highest in Group 1 and lowest in Group 3, showing a statistically significant difference (p=0.047, p=0.000, respectively). The FAZ area and FAZ perimeter circularity index were significantly higher in Group 3 than in Groups 1 and 2 (p=0.017, p=0.000, p=0.020, p=0.000, respectively), with no significant difference between Groups 1 and 2 (p=0.052, p=0.062, respectively). Foveal vessel density did not show a significant correlation with axial length across groups in either SCP or DCP (p=0.005, p=0.036, p=0.138, p=0.111, respectively). Foveal, parafoveal, and perifoveal retinal thicknesses were significantly lower in Group 3 than in Groups 1 and 2 (p=0.015, p=0.000, p=0.000, p=0.000, p=0.000, p=0.000, respectively), with no significant difference between Groups 1 and 2 (p=0.120, p=0.976, p=0.109, respectively). Conclusion: A decrease in SCP and DCP vessel density was observed with increasing axial length in myopic individuals, especially in patients with an axial length of 26 mm or more. FAZ area, retinal thickness, and subfoveal choroidal thickness were also found to be associated with axial length.