Measurement of Ocular Compliance Using iPerfusion

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Physiology

Background:

• The pressure-volume relationship of the eye, crucial for understanding ocular health, is determined by corneoscleral shell biomechanics.
• Ocular compliance (OC), defined as the change in volume per unit pressure change (dV/dP), is vital for evaluating ocular conditions involving volume or pressure fluctuations.
• Accurate measurement of OC, particularly in rodent models, presents a significant challenge in ophthalmic research.

Purpose of the Study:

• To establish and validate reliable methods for measuring ocular compliance (OC) in enucleated mouse eyes.
• To assess the impact of a cross-linking agent, genipin, on ocular compliance in mice.
• To demonstrate the utility of OC measurement as a tool for evaluating corneoscleral biomechanics.

Main Methods:

• Ocular compliance (OC) was measured in 24 enucleated C57BL/6 mouse eyes using the iPerfusion system.
• Controlled pressure steps were applied, and time-varying flow rates were recorded.
• Data were analyzed using "Discrete Volume" and "Step Response" methods for comparison.

Main Results:

• Both "Discrete Volume" and "Step Response" methods yielded similar OC values at 13 mmHg (41-42 nl/mmHg).
• The "Step Response" method provided tighter confidence intervals for individual eye measurements.
• Genipin treatment significantly decreased ocular compliance by 40% (p=0.0001), indicating altered biomechanical properties.

Conclusions:

• The "Step Response" method offers a robust approach for measuring ocular compliance (OC) in mouse eyes.
• OC measurement is a valuable tool for assessing corneoscleral biomechanics in preclinical research.
• This study validates OC measurement as a sensitive indicator of changes in ocular tissue properties.