Abstract: Objective To observe and compare choroidal thickness in highly myopic eyes with dome-shaped macula (DSM) versus those without DSM. Design  Retrospective case series. Participants  A total of 747 patients (1224 eyes) with high myopia who visited the Third Medical Center of PLA General Hospital between February 2024 and February 2025 were included. Among them, 111 eyes had DSM and 1113 eyes did not have DSM. Methods  To control for the potential confounding effect of axial length, 111 eyes without DSM were matched (1:1) to the DSM group based on axial length (difference≤0.2 mm) from the pool of 1113 non-DSM eyes. All patients underwent examination using the radial scanning mode of optical coherence tomography (OCT). In the DSM group, a tangent line was drawn to the posterior pole on the OCT image, intersecting the retinal pigment epithelium (RPE) at two tangent points. Choroidal thickness was measured at these tangent points in each scanning direction (superior, inferior, nasal, temporal, superonasal, inferonasal, superotemporal, inferotemporal). In the non-DSM group, a line was first drawn connecting the fovea to the corresponding outer border of the RPE, and a perpendicular line was dropped from this line. The intersection point of this perpendicular line with the RPE was taken as the center. A circle was drawn using this center point, with a diameter equal to the average baseline width of the matched DSM group. The intersection points of this circle with the RPE served as the tangent points for the non-DSM group, where choroidal thickness was measured in each direction. Main Outcome Measures  Choroidal thickness in each scanning direction. Results  The choroidal thickness at the fovea in the DSM group was (131.17±51.72) μm, significantly higher than that in the non-DSM group (96.28±55.86)μm (P<0.001). The choroidal thickness in the superior, inferior, nasal, temporal, superonasal, inferonasal, superotemporal, and inferotemporal quadrants in the DSM group were (122.71±51.20) μm, (105.07±41.16) μm, (94.32±46.34)μm, (123.25±46.03) μm, (103.18±41.30) μm, (99.38±40.24) μm, (124.06±46.00) μm, and (107.73±42.02) μm, respectively, which were not significantly different from those in the non-DSM group, (133.63±85.81) μm (P=0.910), (115.44±59.87) m (P=0.489), (103.75±50.68) μm (P=0.442), (112.44±75.81) μm (P=0.404), (105.72±55.36) μm (P=0.737), (95.72±41.74) μm (P=0.781), (119.84±65.55) μm (P=0.567), and (114.78±61.72) μm (P=0.583), respectively. Conclusion Changes in choroidal thickness in highly myopic eyes with DSM may be region-specific, characterized by significant thickening in the foveal region but no significant changes in the peripheral choroid.

Key words: High myopia, Dome-shaped macula, Choroidal thickness