High infusion pressure in conjunction with vitreous surgery alters the morphology and function of the retina of rabbits

Abstract

ABSTRACT.Purpose: To investigate the effects of high infusion pressure in conjunction with pars plana vitrectomy (PPV) on retinal morphology and function in rabbits. Methods: Pars plana vitrectomy was performed under urethane (0.8 mg ⁄ kg) anaesthesia in the right eye of albino rabbits following phacoemulsification and aspiration (PEA). The left eyes were not touched. After PEA, the animals were divided into two groups. In six eyes, intraocular pressure (IOP) was increased to 80 mmHg for 30 mins (high-pressure group) and in five eyes IOP was maintained at 40 mmHg for 30 mins (low-pressure group). The IOPs were regulated by the height of the bottle of balanced salt solution (BSS) and monitored with a pressure transducer. After the pressure elevation, vitreous fluid was collected to measure the glutamate concentration. Then, PPV was performed for 15 mins in both groups under an infusion pressure of 40 mmHg. In five additional rabbits, PEA alone was performed in the right eye, and vitreous fluid was collected (PEA group). Functional alterations were assessed by recording visual evoked potentials (VEPs) and electroretinograms (ERGs). Ten days after the IOP changes, the animals were killed with intravenous pentobarbital sodium and the eyes were prepared for histological analysis. Damage to retinal ganglion cells (RGCs) was quantified by counting the number of cells in the ganglion cell layer (GCL). The contralateral eyes in the high-pressure group served as controls (n ¼ 6). Results: The mean implicit time (IT) of the VEPs in the high-pressure group was significantly longer than that before the IOP elevation, by 114)124% (p < 0.05, paired t-test), and also than that of control eyes (p < 0.05, ANOVA followed by t-test). No significant changes in the VEPs were detected in either the low-pressure group or the PEA group. There were significantly fewer cells in the GCL in the high-pressure group (24.7 ⁄ mm) than in the control animals (41.4 ⁄ mm; p < 0.05, Dunnett's test). The number of cells in the GCL in the low-pressure and PEA groups did not significantly differ to that in the controls. The amplitudes of the ERG a-and b-waves were not significantly changed (p > 0.05, paired t-test). Conclusions: These results suggest that high infusion pressure in conjunction with PPV leads to morphological and functional changes in the retina. The absence of ERG changes and presence of VEP changes suggest that these changes were due to damage to RGCs, which supports the morphological observations.

Fluid dynamics in three 25‐gauge vitrectomy systems: principles for use in vitreoretinal surgery

“…Figure 3 shows the areas in which aspiration rates were higher than infusion rates, the 'unsafe zone for vitrectomy', which can result in low intraocular pressure (IOP) (Minami et al 2007). …”

Neuroprotective Effects of a Taurine-Containing Irrigation Solution for Vitrectomy

“…2 Furthermore, it has been shown that photochemical in combination with mechanical stress leads to an increase in glutamate levels in the vitreous humor and retinal ganglion cell (RGC) death. 3,4 Elevated glutamate concentration in the extracellular space of RGCs results in RGC death. [5][6][7] This process of lethal or damaging overstimulation of nerve cells by neurotransmitters is called excitotoxicity.…”

Characterization of the Fluidic Properties of a Syringe-Based Portable Vitrectomy Device

“…Further studies are needed to determine if syringe-generated infusion and aspiration can balance to avoid unsafe fluctuations in intraocular pressure. 15 In conclusion, the Intrector vitrectomy device uses manually controlled syringes for aspiration and infusion. Levels of vacuum and flow for a comfortable plunger pull force were comparable with some commercially available vitrectomy instruments.…”