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Little is known about dynamic IOP differences in the anterior and posterior chambers of the eye
Seo et al. developed minimally-invasive probes with pressure-sensitive transistors and used these to obtain continuous measurements of local IOP values in the anterior chamber and vitreous chamber of living rabbits. They then induced glaucoma in their animal models and compared the local IOP distribution between normal and glaucomatous eyes. They also used rebound tonometry for comparing these measurements.
They found that glaucoma induced higher IOP in the vitreous chamber than in the anterior chamber (+3.8 mmHg on average), a difference that was maintained throughout the measured range of 7-60 mmHg. Of note, the absolute difference in IOP between the vitreous chamber and the anterior chamber increased slightly in the high IOP condition (after the injection of hyaluronic acid into AC until the IOP saturation to the normal range). This absolute difference was less than 3 mmHg in the normal IOP range, but it was more than 3 mmHg in 36% of the points detected at high levels of IOP.
Glaucoma induced higher IOP in the vitreous chamber than in the anterior chamber
Their experimental set-up is solid and maximum care was taken not to influence real IOP through the introduction of the needle-shaped sensors. Their in-vivo findings are also consistent with previous findings in enucleated porcine eyes. Few human studies exist that provide an insight to real-life IOP differences in human eyes. One such approach are IOP measurements with the EyeMate-SC sensor, a device which is placed within suprachoroidal space and measures IOP in the posterior chamber.
Seo et al.'s findings indicate that obtaining IOP measurements closer to the optic nerve may be more relevant for the diagnosis and management of glaucoma patients. It is hoped that more efforts will be invested in improving IOP measurements in the future.