Interocular Symmetry of Choroidal Thickness and Volume in Healthy Eyes on Optical Coherence Tomography

Abstract

Background: We aimed to determine the physiological symmetry, with spectral-domain optical coherence tomography, of choroidal measurements in a healthy population in all the areas defined in the Early Treatment Diabetic Retinopathy Study (ETDRS). Methods: One hundred and fifty-four eyes of 77 healthy young adults between the ages of 19 and 32 years were enrolled. Differences in choroidal thickness (CT) and volume (CV) between the left and right eyes were calculated. Normal ranges of absolute interocular differences were established as the 95th percentile. Results: The mean ± SD subfoveal CT (SFCT) and total CV values in the right and left eyes were 342.03 ± 77.38 versus 361.64 ± 76.45 µm (correlation coefficient ρ = 0.820; p < 0.001) and 0.27 ± 0.06 versus 0.28 ± 0.06 mm³ (ρ = 0.830; p < 0.001), respectively. Differences in 5 of the 9 areas of the ETDRS map were statistically significant (p < 0.05), but with a strong interocular correlation (ρ > 0.8; p < 0.001). The 95th percentile of interocular tolerance limits for CT in the 1-, 3-, and 6-mm areas were 97, 70, and 57 μm, respectively; the 95th percentile for the volume values were 0.06, 0.51, and 1.73 mm³. Conclusions: CT and CV are highly correlated between eyes, statistically significant differences between them can be found, and absolute interocular differences may reach 97 µm in SFCT, and 1.73 mm³ in total CV.

Choroidal Changes of Long-Term Type 1 Diabetic Patients without Retinopathy

“…Our findings show similar results as previously described in CT; CT was thickest in the subfoveal areas, becoming thinner towards the nasal or temporal areas [11,17,18,23,24].…”

“…There are numerous physiological variables such as AL, refractive error, IOP, diurnal variation, other systemic vascular diseases and various drugs that could affect the CT in addition to the different age ranges of the population groups of each study. In this study, we included patients of similar age to avoid the diminution of the CT with age shown in previous works, and AL was a fundamental factor to be taken into account in the measurement of CT [17][18][19][20][21][22]. We tried to exclude confounding factors by looking for young people with good control, and considerable refractive errors were discarded to avoid bias.…”

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

“…Despite the various differences in CTs reported in each paper, most studies 13,[29][30][31][32] indicated that interocular CTs measured in the foveal and parafoveal areas showed overall high correlation coefficients or ICC values (r > 0.8, ICC >0.9). In our study, CTs showed relatively high agreement (r > 0.8, ICC >0.9) at the subfoveal, nasal 5, nasal 6, temporal 1, and temporal 2 points, corresponding to the center and inner ring (3-mm diameter centered on the fovea) of the Early Treatment Diabetic Retinopathy Study (ETDRS) map.…”

“…Conversely, a few reports found the CT of the macula was thicker in left eyes than in right eyes. 13,31 The discrepancies among these studies are presumably related to various factors that can influence CT, such as inaccurate measurement, patient demographics (e.g. sex, age, AL, and SE), diurnal variation, and IOP.…”

“…There have been several reports regarding the interocular symmetry of CT. [29][30][31][32][33][34] However, most studies have focused on CT around the macula. To the best of our knowledge, no study has compared the interocular symmetry of CT in the peripheral area using wide-field SS-OCT.…”