Pressure Difference between the Anterior Chamber and the Vitreous Cavity in Eyes with Pupillary Block

Abstract

 

Purpose

 

The primary aim of this study was to measure the pressure difference between the anterior chamber and the vitreous cavity, which had been predicted with studies with mathematical models, in real eyes.

 

Methods

 

This study was conducted using vitrectomized porcine eyes. Infusion pressures of 10 to 80 mmHg were generated with vented gas forced infusion system. Measurement of pressure were obtained with digital manometry connected with 25-gauge catheters from the anterior chamber and vitreous cavity, simultaneously. After increasing the pressure of the anterior chamber to each target pressure, pressure change in the vitreous cavity were recorded, and vice versa.

 

Results

 

The obtained intravitreal pressure was similar to the increased intracameral pressure in all cases. The obtained intracameral pressure was similar to the increased intravitreal pressure, under 50 mmHg. When increasing the intravitreal pressure to 60, 70 and 80mmHg, the obtained intracameral pressure were 57.6 ± 1.0, 64.0 ± 0.8, and 69.6 ± 2.4 mmHg, respectively. The obtained intravitreal pressures were 1.5, 5.9 and 9.1 mmHg higher than that of the obtained intracameral pressure with target pressures of 60, 70, and 80mmHg, respectively (P = 0.027, 0.001, 0.001). Pupillary block was observed in case of increasing the intravitreal pressure over 50 mmHg.

 

Conclusions

 

The intracameral pressure could be significantly lower than intravitreal pressure in some eyes with pupillary block. When we use the non-invasive tonometer, the possibility of underestimation of operative pressure at the optic nerve head should be considered in eyes with pupillary block.

 

 

Figure 1. Obtained pressure from vitreous cavity (VC) or anterior chamber (AC) with various pressure setting of the anterior chamber or vitreous cavity.

 

 

Figure 2. Pressure transmission from the vitreous cavity to the anterior chamber in normal eye (left) and eye with pupillary block (right). Aqueous humor can freely flows to the anterior chamber and the vitreous cavity in normal eye (arrows). In the eyes with pupillary block, lens and iris act as a flexible physical barrier for aqueous flow. Higher pressure in vitreous cavity is partially transmitted to anterior chamber not directly through the fluid molecule itself, but only indirectly through the bulging of the iris (dotted arrows).

 

Keywords: 568 intraocular pressure • 427 aqueous • 667 pupil