Choroidal vascularity index changes during the Valsalva manoeuvre in healthy volunteers

Abstract

To evaluate the effects of the Valsalva manoeuvre (VM) on the choroidal vascularity index (CVI) in healthy volunteers.Methods: This prospective, cross-sectional study included 60 eyes of 30 healthy volunteers. Enhanced depth imaging-optical coherence tomography scans of both eyes involving the fovea were taken, and a 1500 μm subfoveal choroidal area was selected for image binarization with open-access Fiji software. The binarized image was segmented into the stromal area (SA) and luminal area (LA), and CVI was calculated as the ratio (%) of LA to the total choroidal area (TCA). CVI, subfoveal choroidal thickness (SFCT), IOP, systolic and diastolic blood pressure were evaluated at rest and during the VM.Results: During the VM, a mean ± standard deviation increase in LA (0.02 ± 0.05 mm 2 , p < 0.001) and CVI (1.72 ± 2.83%, p < 0.001) was observed, whereas SA (−0.02 ± 0.05 mm 2 , p < 0.001) decreased. There was no significant change in TCA (0.00 ± 0.03 mm 2 , p = 0.55) or SFCT (1.05 ± 10.92 μm, p = 0.46). There was a moderate positive correlation between the spherical equivalent refractive error (SE) and SFCT both at rest and during VM (r 58 = 0.49, p < 0.0005 and r 58 = 0.49, p < 0.0005, respectively). However, there was no significant correlation between SE and CVI either at rest or during VM (p = 0.11 and 0.06, respectively). In a multiple linear regression analysis, CVI was only associated with SFCT; however, SFCT was also associated with SE, both at rest and during VM (p < 0.001). Conclusion: Valsalva manoeuvre increases CVI by choroidal vascular dilation as demonstrated by an increase in LA and a decrease in SA. Researchers should be careful about unintentional VM during examinations. K E Y W O R D S choroidal vascularity index, enhanced depth imaging optical coherence tomography, subfoveal choroidal thickness, Valsalva manoeuvre How to cite this article: Sevik MO, Çam F, Aykut A, Dericioğlu V, Şahin Ö. Choroidal vascularity index changes during the Valsalva manoeuvre in healthy volunteers.

Authors' Reply

“…However, the images captured at different times from different participants may be affected by several other conditions such as uneven illumination, a difference in focusing and even differences in the direction of light, resulting in variations in image contrast and brightness 4 . An example of such variation is seen in Figure 1 of our paper, 1 which also gave rise to the subject matter of this correspondence. Dr. Reda and colleagues suggest that the contrast variation in Figure 1c,d could explain our findings of increased luminal areas during VM (Figure 1a,b).…”

“…We would like to thank Dr. Reda and colleagues for their interest in our recently published study assessing choroidal vascularity index (CVI) changes during the Valsalva manoeuvre (VM). 1 Reda et al stated their concerns as to whether the reflectivity or contrast of the enhanced depth imaging (EDI)-optical coherence tomography (OCT) images captured before and after the VM might have effects on the observed difference in CVI by referring to the blooming effect seen in ultrasonography (USG). 2 Although this concern appears valid, the blooming effect seen in USG occurs when the gain setting, and therefore the resolution, is not standardised while acquiring B-scan images.…”

“…As described in the Method section of the paper, 1 we adopted the binarisation method of Agrawal et al using the open access Fiji software (http://fiji.sc). 4,5 From Otsu's global, Bernsen's local, Phansalkar's local and Niblack's local thresholding techniques, Agrawal et al chose Niblack's autolocal thresholding technique to binarise greyscale EDI‐OCT B‐scan images to overcome the previously mentioned contrast and brightness variations found in different individuals without any brightness adjustment 4,5 .…”

Choroidal vascularity index changes during the Valsalva manoeuvre in healthy volunteers

“…[7][8][9] This artefact is also present with OCT and will influence the binarisation used in the CVI evaluation, thereby increasing the low reflective areas (luminal) when the amplification is low, and reducing them when the amplification is higher. This effect is clearly visible in figure 1c,d of the paper, 1 where the reflectivity is lower in the pictures obtained during the Valsalva manoeuvre, and this could explain the authors' findings of increased luminal areas.…”

“…To the Editor, We read with great interest the article by Sevik et al concerning choroidal vascularity index changes during the Valsalva manoeuvre in healthy volunteers. 1 We congratulate the authors for their very interesting study, but would like to make some comments.…”