Pressure difference between the anterior chamber and the vitreous cavity in eyes with pupillary block

Real-time in vivo monitoring of intraocular pressure distribution in the anterior chamber and vitreous chamber for diagnosis of glaucoma

Glaucoma causes irreversible vision loss due to optic nerve damage and retinal cell degeneration. Since high intraocular pressure (IOP) is a major risk factor for glaucoma development, accurate IOP measurement is crucial, especially intravitreal IOP affecting the optical nerve and cells. However, conventional methods have limits in selectively and directly detecting local retina pressure. Here, we present continuous measurements of local IOP values in the anterior chamber and vitreous chamber of living animals using minimally invasive probes with pressure-sensitive transistors. After inducing glaucoma in animal models, we compared the local IOP distribution between normal and glaucomatous eyes. We also compared IOP values detected in the cornea using tonometry measurements. Our findings revealed that glaucoma induced higher IOP in the vitreous chamber than in the anterior chamber, indicating that measuring IOP in the vitreous chamber is key to the glaucoma model. This progress offers future directions for diagnosis and treatment of glaucoma.

Investigation of intraocular pressure of the anterior chamber and vitreous cavity of porcine eyes via a novel method

To evaluate a new method of measuring the intraocular pressure (IOP) in the vitreous cavity. IOPs in the anterior chamber and vitreous cavities of 24 porcine eyes (12 eyes with lenses and 12 eyes without lenses) were measured directly, continuously, and simultaneously. We used a needle as a part of the pressure sensor to measure the anterior chamber IOP and a disk-shaped sensor to measure the vitreous cavity IOP. A significant group-by-condition interaction on the vitreous cavity IOP between the two groups (phakia and aphakia) and four conditions of anterior chamber IOP were observed (F[3,258] = 5.8564, p < 0.001). A positive correlation was observed between the vitreous cavity IOP and anterior chamber IOP in both the phakia group (R = 0.96, p < 0.001) and the aphakia group (R = 0.97, p < 0.001). No significant correlation was observed between the ΔIOPv-a (vitreous cavity IOP - anterior chamber IOP) and anterior chamber IOP in either group (phakia group: R =  - 0.18, p = 0.034; aphakia group: R =  - 0.029, p = 0.73). The vitreous cavity IOP measured with the new sensor was well-correlated with the anterior chamber IOP in the physiological range tested.

Time Course Changes of the Mechanical Properties of the Iris Pigment Epithelium in a Rat Chronic Ocular Hypertension Model

BACKGROUND

The flow field of aqueous humor correlates to the stiffness of iris pigment epithelium (IPE) which acts as a wall of posterior chamber. We focus on the variations of IPE stiffness in a rat ocular hypertension (OHT) model, so as to prepare for exploring the mechanism of duration of OHT.

METHODS

Episcleral venous cauterization (EVC) was applied on one eye of male adult Sprague-Dawley rats to induce chronic high intraocular pressure. According to the duration of OHT (0, 1, 2, 4, and 8 weeks), rats were randomly divided into Gw0, Gw1, Gw2, Gw4, and Gw8. Atomic force microscope (AFM) analysis was applied to test IPE stiffness in three regions: iris root, mid-periphery, and pupillary-margin in each group. Histological changes of IPE were also examined in Gw4 and Gw8.

RESULTS

There was an overall growing tendency of IPE stiffness in EVC eye. IPE in EVC eye was significantly stiffer than fellow eye in Gw2, Gw4, and Gw8 (in iris root, mid-periphery, and pupillary-margin, p<0.05). IPE in EVC eye in pupillary-margin was significantly stiffer than iris root in Gw4 and Gw8 (p<0.05). In EVC eye, IPE becomes thinner and IPE cell density decreases.

CONCLUSION

IPE stiffness increases gradually with the duration of chronic high intraocular pressure.