Report: Choroidal Thickness of Wide-Field Regions ‘Bilaterally Symmetrical’

Analysis of interocular symmetry of choroidal thickness using wide-field swept-source optical coherence tomography (SS-OCT) found that the choroidal thicknesses (CTs) of each region were bilaterally symmetrical in young healthy individuals, but CT differences increased from the center of the periphery, according to a study in Investigative Ophthalmology & Visual Science.

This difference “indicated that the anatomic variation of the nasal peripapillary and peripheral choroid was greater than that of the macula,” according to investigators. 

In the study, each of the 32 participants (19 men and 13 women, average age of 27.75 ± 2.32 years) had a wide-field 16 mm 1-line scan on SS-OCT. Twelve points were used to measure CTs: 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 μm and 5400 μm from temporal point 3 (peripheral area). 

Investigators measured bilateral CTs and analyzed the correlations and differences in the corresponding regions.

They found no statistically significant differences in CTs between the right and left eyes in all corresponding areas (P >.05). All patients had significant positive correlation coefficients (P <.001). However, the study shows nasal peripapillary and peripheral areas had relatively low correlation coefficients, compared with macular areas. “In addition, the bilateral CT differences were 32.60 μm ± 25.80 μm in the macular area, 40.67 μm ± 30.58 μm in the nasal peripapillary area, and 56.03 μm ± 45.73 μm in the peripheral area (P < 0.001),” the study says.

“Interocular CTs generally showed significant symmetries, although there were differences in degree depending on the area,” the report adds. “In addition, analysis of the association between interocular CT differences and other clinical factors revealed that only interocular CT and AL differences in the macular area showed meaningful results. This suggests that the interocular CT difference in the nasal peripapillary and peripheral areas is due to anatomic variation alone, rather than other clinical factors.”

“Physicians should be aware of the possibility of interocular CT differences depending on the area; when a patient exhibits a CT difference beyond the normal limit, it is important to perform detailed examinations to identify any factors or other ophthalmic diseases that might affect CT,” they state.

The study’s limitations include that CTs were measured manually, which might have caused some inaccurate measurements. In addition, investigators didn’t consider differences in retinal image magnification caused by differences in axial length. And, nonindependency of the measured values could have potentially affected statistical power. Also, vertical SS-OCT scans, including superior and inferior areas, were not included. Finally, they didn’t analyze other factors that might impact CT.

Reference

Kim MS, Lim HB, Lee WH, et al. Wide-field swept-source optical coherence tomography analysis of interocular symmetry of choroidal thickness in healthy young individuals. Invest Ophthalmol Vis Sci. 2021;62(3):5. doi: 10.1167/iovs.62.3.5