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Michael Dattilo, Brian C Samuels, C Ross Ethier; Tree Shrew Spontaneous Retinal Venous Pulsation Changes Due to Changes in the Translaminar Pressure Difference. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2306.
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© ARVO (1962-2015); The Authors (2016-present)
Spontaneous retinal venous pulsations (SRVPs), pulsations of branches of the central retinal vein (CRV) on the optic disc, are known to be affected by the translaminar pressure difference (TLPD = intraocular pressure (IOP) – intracranial pressure (ICP)). SRVPs occur less frequently and have smaller amplitudes in glaucoma patients, are absent in syndromes of elevated ICP, and are used clinically to qualitatively assess ICP. Although SRVPs are influenced by the TLPD, the exact relationship between SRVPs, IOP, and ICP remains uncertain.
SRVP screening: Live en face optical coherence tomography (OCT) video output of the retinal vasculature of anesthetized adult tree shrews was recorded and analyzed using Matlab to determine SRVP incidence under normal physiologic conditions (+SRVP) and to quantify CRV diameter changes.IOP & ICP manipulation: Under anesthesia, the intracranial cerebrospinal fluid-containing space and the anterior chamber of a +SRVP tree shrew were cannulated. ICP was pressure clamped at 7 mmHg and IOP was incrementally changed from 5 to 30 and back to 5 mmHg. ICP was increased to 30 mmHg and the IOP protocol was repeated. SRVP changes were recorded and analyzed.
SRVPs were detected in 12/16 (75%) tree shrews. In a pilot experiment on a +SRVP tree shrew, an IOP of 10 mmHg was necessary to generate SRVPs at an ICP of 7 mmHg, with multiple veins having SRVPs at IOPs above 15 mmHg. At an ICP of 30 mmHg, the IOP necessary to generate SRVPs increased to 20.5 mmHg, with multiple veins having SRVPs at IOPs above 20.5 mmHg. Increasing ICP also affected SRVP amplitude; SRVP amplitude was smaller at an ICP of 30 mmHg compared to an ICP of 7 mmHg.
Tree shrew SRVP frequency is similar to the reported human SRVP frequency. Tree shrew SRVP characteristics are also affected by TLPD changes in a manner similar to humans. Therefore, tree shrews likely are a good animal system to further study SRVPs. Since there does not appear to be a simple, one-to-one correlation between changes in the TLPD and changes in SRVP characteristics, more studies are necessary to further understand the complex relationship between SRVPs, IOP, and ICP and to give further insights into the clinical utility of monitoring changes in SRVPs in glaucoma and in syndromes of elevated ICP.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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