Interocular asymmetry in choroidal thickness in healthy Indian population using swept-source optical coherence tomography

Interocular asymmetry of choroidal thickness and vascularity index measurements in normal eyes assessed by swept-source optical coherence tomography

BACKGROUND

To investigate the symmetry of interocular choroidal thickness and vascularity index measurements in normal eyes using swept-source optical coherence tomography (SS-OCT). Cross-sectional and observational study. This study included 244 eyes of 122 normal adults with ages uniformly distributed from 19 to 89 years.

METHODS

SS-OCT imaging was performed using a scanning pattern of 12×12 mm. Mean choroidal thickness (MCT) and choroidal vascularity index (CVI) measurements in the entire scanning region were obtained using a validated and published automatic method. The correlation and differences (including signed and absolute differences) between bilateral MCT and CVI measurements were analyzed at the following 6 regions: 3 concentric circles centered on the fovea with diameters of 2.5, 5, and 11 mm; the inner rim from 2.5 to 5 mm circle; the outer rim from 5 to 11 mm circle; and the entire 12×12-mm scan region, respectively. Comparison of interocular MCT and CVI measurements.

RESULTS

MCT measurements in right and left eyes were strongly correlated in all regions [all intraclass correlation (ICC) >0.73], but MCT measurements in right eyes were significantly thicker than in left eyes. CVI measurements in right and left eyes were moderately correlated in all regions (all ICC >0.46), but CVI measurements in right eyes were significantly smaller than that in left eyes in the macular subregions (2.5 mm circle, 5 mm circle, and the inner rim). Neither signed nor absolute interocular differences in MCT were correlated with corresponding CVI interocular differences.

CONCLUSIONS

Choroidal differences exist between normal fellow eyes in adults in the absence of obvious pathology. This study is useful in assisting clinicians and researchers in distinguishing asymmetric changes that are to be expected in normal eyes versus changes that could be associated with diseases.

Wide-Field Swept-Source Optical Coherence Tomography Analysis of Interocular Symmetry of Choroidal Thickness in Healthy Young Individuals

Purpose

The purpose of this paper was to study the bilateral choroidal thickness (CT) symmetry and differences in healthy individuals using wide-field swept-source optical coherence tomography (SS-OCT).

Methods

All participants underwent a wide-field 16-mm 1-line scan using SS-OCT. CTs were measured at the following 12 points: 3 points at 900 µm, 1800 µm, and 2700 µm away from the nasal optic disc margin (nasal peripapillary area), 1 point at the subfovea, 6 points at 900 µm, 1800 µm, and 2700 µm away from the subfovea to the nasal and temporal areas (macular area), and 2 peripheral points at 2700 and 5400 µm from temporal point 3 (peripheral area). Bilateral CTs were measured; their correlations and differences in the corresponding regions were analyzed.

Results

There were no statistically significant differences in CTs between the right and left eyes in all corresponding areas (all P > 0.05); they all showed significant positive correlation coefficients (r) (all P < 0.001). However, the nasal peripapillary and peripheral areas had relatively low correlation coefficients, compared to the macular areas. In addition, the bilateral CT differences were 32.60 ± 25.80 µm in the macular area, 40.67 ± 30.58 µm in the nasal peripapillary area, and 56.03 ± 45.73 µm in the peripheral area (all P < 0.001).

Conclusions

Overall, the CTs of each region were bilaterally symmetrical. However, the differences in CTs increased from the center to the periphery, which indicated that the anatomic variation of the nasal peripapillary and peripheral choroid was greater than that of the macula.