Choroidal Biomarkers: A Repeatability and Topographical Comparison of Choroidal Thickness and Choroidal Vascularity Index in Healthy Eyes

Abstract

Purpose Choroidal thickness (ChT) and choroidal vascularity index (CVI) represent two important metrics in health-, disease-, and myopia-related studies. Wide-field swept-source optical coherence tomography (OCT) provides improved and extended imaging and extraction of choroidal variables. This study characterizes the topography and repeatability of these parameters in healthy eyes. Methods Swept-source OCT volume scans were obtained on 14 young adult patients on three separate days. ChT and CVI were automatically corrected for image magnification and extracted for different enface regions within an extended ETDRS grid of 10 mm diameter. Topographical distribution, correlation to ocular length, and intersession repeatability of both choroidal parameters were assessed. Results CVI showed little fluctuation between subfields, unlike ChT, which demonstrated thinning toward the peripheral choroid (coefficients of variation 5.92 vs. 0.89). ChT showed a consistent negative correlation with axial length (ρ = −0.05 to −0.61), although this was only statistically significant in the inner superior subfield ( P = 0.02). There was no consistent or significant relationship between CVI and axial length or between CVI and ChT. The repeatability of CVI measurements (3.90%–5.51%) was more consistent between scan regions than ChT measurements (10.37–20.33 µm). Conclusions CVI values were consistent across the central 10 mm of the retina, while ChT reduced with eccentricity. The repeatability of both parameters is similar to the effect size reported in many studies using the choroid as a biomarker, which should be considered in the interpretation of findings. Translational Relevance This study provided normative as well as metrological information for the clinical interpretation of ChT and CVI in health and disease.

Peripapillary Choroidal Vascularity Outside the Macula in Patients With Central Serous Chorioretinopathy

“…Many studies have shown variations in subfoveal CVI. Breher et al 22 reported that CVI showed little fluctuation between early treatment diabetic retinopathy study subfields in normal subjects, unlike CT, which demonstrated thinning toward the peripheral choroid. However, Singh et al 42 reported that CVI showed significant regional variation, with the macular segment showing the lowest CVI and nasal segments the highest CVI in both CSC and fellow eyes.…”

“…In addition, they suggested that the CVI is a more robust marker of choroidal diseases. Breher et al 22 showed that CVI had little fluctuation between subfields, unlike CT. In recent studies, 4,[23][24][25] increased CVI has been noted in acute and chronic CSC; however, further studies are required to clarify the relationship between these two biomarkers obtained from OCT imaging, CT, and CVI, and their roles in pathophysiology.…”

Comparison of choroidal hyperreflective spots on optical coherence tomography images between both eyes of normal subjects

“…Agrawal et al (24) reported that in healthy subjects, CVI was less affected by demographic factors such as age and axial length than choroidal thickness. Breher et al (27) showed little variation in the CVI across the 10-mm center of the posterior pole, whereas choroidal thickness decreased with increasing eccentricity. Most studies reported decreased luminal and total choroidal areas with increasing age in normal subjects (28)(29)(30)(31).…”

“…Recent advances in optical coherence tomography (OCT) technology have allowed for better in vivo visualization of the choroidal architecture. Recent OCT studies have used image binarization methods to determine the relative ratios between the vascular or stromal components of the choroid, such as the choroidal vascular index (CVI) (24)(25)(26)(27)(28). Agrawal et al (24) reported that in healthy subjects, CVI was less affected by demographic factors such as age and axial length than choroidal thickness.…”

“…However, most studies have reported that the CVI decreases with increasing axial length. (24,27,28) The ratio of stroma to vessels has been suggested as a key component influencing the choriocapillaris flow and is also involved in the pathogenesis of various chorioretinal diseases (11,(33)(34)(35)(36)(37). However, few studies have focused on the choroidal stroma and analyzed their characteristics in en face OCT images of normal subjects.…”