Effect of variations of corneal physiology on novel non-invasive intraocular pressure monitoring soft contact lens.

Glaucoma is the leading cause of irreversible blindness around the world. With its slow asymptomatic progression, there is an emphasis on early detection and frequent monitoring. A novel microfluidic contact lens has been established as a potential way to track the fluctuations of the intraocular pressure (IOP) which is a key indicator for diagnosing and monitoring glaucoma progression. The purpose of this article is to determine the effect of physiological variations of the eye on the performance of the microfluidic contact lens. Ultrasound biomicroscopy (UBM) was used to measure the central corneal thickness (CCT) and radius of corneal curvature (RCC) for a series of 16 fresh enucleated porcine eyes. The effect of these corneal anatomic features on device performance was then assessed by systematically adjusting intraocular pressure from 10 to 34 mmHg and monitoring the device indicator response. The performance of the microfluidic contact lens was determined by finding the amount the indicator fluid shifted in position as a result of 1 mmHg IOP increase. The relationship between IOP and indicator fluid was found to be linear for all eyes. The slope of the indicator fluid movement as a result of the IOP was evaluated against the CCT and RCC of each porcine eye. This yielded low correlation coefficients, 0.057 for CCT and 0.024 for RCC, meaning that these physiological differences showed no systematic impact on the measurements made with the contact lens.

Correlation between corneal and contact lens deformation with changes in intraocular pressure for wearable monitoring systems.

OBJECTIVE: The aim of this work is to evaluate the extent to which the eye's curvature deformation, due to changes in the intraocular pressure (IOP), can be directly tracked by an overlying contact lens. METHOD: In this experimental study, using 12 cadaveric eyes, the IOP was increased from 10 to 36 mmHg, while video imaging was used to capture the three experimental variations. The deformation of the bare eye was used as a control, while the deformation of an overlying silicone grided contact lens and an overlying microfluidic IOP-sensing contact lens were examined and compared. RESULTS: The relation between the slope of the radius of corneal curvature versus the IOP for both the bare eye and the marker contact lens yielded a linear relationship with a R2 value of 0.83. The microfluidic contact lens resulted in an average performance of 0.40 mm indicator movement/mmHg (SD 0.006). Comparing the slope of the marker contact lens deformation, to the performance of the microfluidic contact lens resulted in a R2 value of 0.78. The strain map of the overlaying grided contact lens showed most deformation occurring along the outer edge of the lens with increased deformation as increase IOP occurs; as well as with some negative, compressive movement near the central points. CONCLUSION: The deformation from the curvature of the eye is significant enough from 10 to 36 mmHg that a silicone contact lens can capture and mimic those changes. The results show promise for optimization in contact lens-based IOP monitoring.

Non-invasive Intraocular pressure monitoring with contact lens.

BACKGROUND: Glaucoma is the second leading cause of blindness in the world and the first leading cause of irreversible vision loss. Currently, the primary methodology of testing for the intraocular pressure (IOP) is during clinical office hours, which only provide a limited amount of information on the trends and fluctuations of the IOP. Therefore, a continuous monitoring system is required to properly determine the peaks of pressure and to negate any false results obtained by sparse, clinic hour testing. The objective of this study is to determine the ability of a newly designed contact lens with an embedded microchannel, to accurately measure the fluctuations in the IOP. METHODS: Experimentation was completed on fresh enucleated porcine eyes. The contact lens was placed on the porcine eye and utilising a camera the fluid movement, within the microchannel in the contact lens, was recorded. A micro-pressure catheter, threaded into the centre of the vitreous chamber, recorded the true IOP and was compared with the displacement of the indicator fluid within the microchannel. RESULTS: The contact lenses showed a consistent linear responsiveness to changes in IOP and robust to the effects of anatomical differences among eyes. The indicator fluid had an average fluid movement of 28 um/mm Hg between all the trials. Additionally, the devices showed the ability to measure both increases and decreases in IOP during cyclical fluctuations. CONCLUSION: The described inexpensive and non-invasive sensor is able to reliably monitor the IOP changes based on porcine eye model.