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Yanhui Ma, Sunny Kwok, Keyton Clayson, Xueliang Pan, Jun Liu; Morphological changes in Bruch’s membrane opening during intraocular pressure elevation. Invest. Ophthalmol. Vis. Sci. 2019;60(11):PB0181.
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© ARVO (1962-2015); The Authors (2016-present)
To quantify the changes in the location and diameter of Bruch’s membrane opening (BMO) in response to acute intraocular pressure (IOP) elevation by using ultrasound imaging.
Whole globe inflation tests were performed in 7 human donor eyes (age: 31-74 years old) by increasing IOP from 5 to 50mmHg with 0.5mmHg steps below 30mmHg and 2mmHg steps above. The IOP was held constant at each pressure level for 30 seconds. Cross-sectional images of the posterior eye centered on the optic nerve head (ONH) were acquired along the superior-inferior meridian at each pressure step using a 50MHz ultrasound probe (MS700, Vevo2100, VisualSonics). Two Bruch’s membrane termination points were manually delineated in all B-mode images (i.e., at pixel level) (Fig.1). Center and length of the line connecting these two points was tracked at each pressure step to investigate the morphological change of BMO during IOP elevation. Displacements and changes of BMO were calculated relative to the location and diameter of BMO at the baseline pressure (i.e., 5mmHg). Distributive displacement of the posterior eye was calculated by an ultrasound speckle tracking algorithm.
BMO moved posteriorly and the posterior displacement increased with increasing IOP (71.7±51.9µm at 25mmHg and 129.9±82.4µm at 50mmHg) (Fig.2A). Displacement of BMO was larger than the average within ONH at every IOP level (all p<0.001), and highly correlated with the displacement of ONH (R>0.95) (Fig.2B). A negative displacement gradient was observed in the ONH in the through-thickness direction (Fig.2C). The initial BMO at the baseline pressure ranges from 1224.7 to 1609.4µm (1470.2±133.7µm). Change of BMO diameter is minimal in response to IOP elevation (Fig.2D).
We previously reported that there was minimal expansion of the scleral canal (on average about 20 mm) when IOP was raised from 5 to 30mmHg (Ma et al, IOVS, 2019). This study showed minimal change in BMO diameter. BMO moved more posteriorly than the ONH as a whole.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.
Fig.1 Delineation of BMO terminations on ultrasound image
Fig.2 (A) Displacement of BMO and ONH (B) correlation of BMO and ONH displacement (C) color map of posterior displacement for a representative human donor eye (D) change of BMO diameter(n=7)
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