Measuring Outflow Facility And Ocular Compliance In Ex Vivo Mouse Eyes Using A Syringe-pump System

Summary

Integrating analytical approaches from established pressure-controlled perfusion methods optimized a simple, low-cost syringe-pump system for assessing outflow facility and ocular compliance in mouse eyes.

Abstract

Maintaining intraocular pressure (IOP) at a suitable and stable level is essential for ocular health. The biomechanical properties of the trabecular meshwork (TM), Schlemm’s canal (SC), and the entire corneoscleral shell play a crucial role in IOP homeostasis. Outflow facility (C) is a key parameter for evaluating the effectiveness of TM and SC in draining aqueous humor, while ocular compliance (ϕ) reflects the elasticity of the corneoscleral shell and transient outflow through TM and SC. Previously, a simple, cost-effective syringe-pump system was developed to assess C. However, using simple linear regression for in vivo data analysis has limitations in characterizing TM and SC function. In this study, the syringe-pump system was optimized by applying analytical approaches developed for established pressure-controlled ocular perfusion systems. The measured C and ϕ values in ex vivo eyes were compared with previously published perfusion-system values and were consistent with those reported ranges. In summary, this straightforward, low-cost syringe-pump system facilitates the evaluation of the biomechanical properties of TM and SC.

Introduction

Maintaining a suitable and stable level of intraocular pressure (IOP) is essential for ocular health¹. Sustained elevation in IOP is the primary risk factor for glaucoma^2,3. Long-term IOP fluctuations over months or years also contribute to vision loss^4,5. Recent studies identified another form of IOP fluctuation, transient fluctuations caused by daily activities, which may also accelerate glaucoma progression^6,7. For example, a 46-year-old man with a 20-year history of ....

Protocol

All experiments were conducted in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research and the laboratory animal care and use guidelines of Qingdao University Medical Center (QDU-AEC-2022069).

1. Animal selection and handling

1. Use 5-month-old mice with a 50% C57BL/6 and 50% BALB/c genetic background. Do not consider sex in the experimental design.
2. Maintain mice under a 12 h/12 h light–dark cycle at 23 ± 2 °C and humidity of 50 ± 5%.

2. IOP measurement

1. Anesthetize mice using 2.5% isoflurane with 80% (vo....

Results

The performance of the optimized syringe-pump system was evaluated by comparing C and ϕ in 5-month-old mice with previously published values from pressure-controlled ocular perfusion studies. The normality of datasets in Figure 2F was assessed using the Shapiro–Wilk test, and statistical comparisons were performed using a two-tailed paired Student’s t-test.

As shown in Figure 2A–C, the IOP, C_r,eye,.......

Discussion

This study presents an optimized syringe-pump system for estimating outflow facility and ocular compliance in mouse eyes, yielding values consistent with those reported using pressure-controlled ocular perfusion systems. The present approach improves the accuracy of syringe-based measurements while maintaining a simple and accessible experimental setup. This combination of methodological refinement and accessibility may facilitate broader adoption in laboratories where more advanced systems are not readily available.

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Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Reagent	1× PBS Buffer	Thermo Fisher Scientific	10010023
Isoflurane	Shenzhen Rewoode Life Sciences Co., Ltd., China	R640
Material	100 μL High Precision Syringe	Hamilton	1710
Borosilicate Glass	Sutter, Novato, CA	BF100-50-10
Disposable sterile syringe	Fenglin Medical Devices Co., Ltd. Jiangxi, China	10 ml
Pressure Sensor	IcuMedical	PX26-015G
Silicone tube	Runze Fluid Co., Ltd, Nanjing, China	N/A
Transparent PTFE tube	Runze Fluid Co., Ltd, Nanjing, China	N/A
Equipment	Flaming/Brown pipette puller	Sutter, Novato, CA	P-97
Manual Micromanipulator	World Precision Instruments (WPI)	M3301
Metal bath	Beaver Biology, Suzhou, China	2016C
MicroForge	Narishige Scientific Instrument Lab., Tokyo, Japan	MF830
Micropipette Grinder	MPInstrument Co., Ltd., Wuhan, China	KDG-02
PZMIII Stereo Zoom Binocular Microscope	World Precision Instruments (WPI)	PZMIII
Syringe-Pump	World Precision Instruments (WPI)	AL-1000