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Reiko Yamagishi, MEGUMI HONJO, Makoto Aihara; Effect of IOP-lowering drugs on episcleral venous pressure in mouse eye.. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2712.
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Anti-glaucoma drugs are known to lower intraocular pressure due to enhancement of aqueous outflow and suppression of aqueous humor production. Additionally, episcleral venous pressure (EVP) is involved in intraocular pressure (IOP) regulation via trabecular aqueous outflow. In this study, we examined the effect of Rho-kinase inhibitor (ripasudil), α2 receptor agonist (brimonidine) and parasympathomimetic drug (pilocarpine) on the EVP in mice.
A single drop with 3µl of saline, 0.4% ripasudil, 0.1% brimonidine and 1% pilocarpine were topically applied into randomly selected one of two eyes in ddY mouse. At 30 or 60 minutes after instillation, IOP was measured by microneedle method. EVP was measured using modified microneedle methods, at 30 or 60 minutes after instillation. Microneedle was inserted into the anterior chamber, and the height reservoir was lowered at a rate of 0.5 mmHg / min. The pressure in which the blood reflux in the Schlemm’s canal was first observed was recorded as EVP. The measurement was repeated three times for each measurement, and the average was used as data.
EVP (mmHg) of saline, ripasudil, brimonidine, and pilocarpine were 13.68±0.29, 12.52±0.18, 12.83±0.14, and 13.27±0.60 at 30 minutes, and 13.43±1.09, 12.87±0.77, 12.92±0.65, and 13.26±2.53 at 60 minutes after administration, respectively. EVP was significantly lowered with ripasudil and brimonidine compared to saline (p<0.01) at 30 minutes when the peak IOP reduction by ripasudil and brimonidine was observed. However, no significant difference was observed in any group of EVP at 60 minutes after administration.
Ripasudil and brimonidine lowered EVP in mice. This effect may be additional mechanism of actions to reduce IOP in conventional outflow pathway.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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