Abstract
Purpose:
To measure the intraocular pressure (IOP) during the manual Perfluorocarbon Liquid (PFCL) injection in a simulated pars plana vitrectomy (PPV) using 23 and 25 Gauge infusion ports in a model of human eye
Methods:
A UV photo-crosslinkable polymer model of the human eye was employed to measure the absolute pressure from three sensors during the manual injection of PFCL in a simulated 23 and 25 Gauge PPV. The IOP has been collected by 3 sensors, both in 23 and 25 G, in three experimental settings: in the controlled Venting Gas Forced Infusion (VGFI) of Balanced Salt Solution (BSS) at 30 mmHg with closed eyeball, in VGFI of F-Decalin at 8 PSI and 12 mmHg of preset BSS infusion, and finally in the manual injection of PFCL at 12 mmHg preset BSS infusion. Two experienced vitreoretinal surgeons have repeated twice the manual injection of PFCL (F-Decalin, Fluoron Gmbh, Ulm, Germany) in order to simulate the real situation during PPV with a Stellaris PC vitrectomy machine (Bausch+Lomb, Rochester, NY, USA)
Results:
In the VGFI of BSS in closed eyeball at 30 mmHg, the IOP resulted higher than the preset, but constant (23G: mean 43.70 ± 0,65 mmHg; 25G: mean 47.89 ± 0.13 mmHg). In the VGFI injection of PFCL at 8 PSI and 12 mmHg of BSS infusion, the IOP shown a little variation (23G: mean 29,03 ± 0,31 mmHg; 25G: mean 27,56 ± 0,20 mmHg) whereas a wide range in IOP values has been detected during the manual F-Decalin injection at 12 mmHg of BSS infusion (23G: min 17.64, max. 120.70, mean 55.25 ± 13.14 mmHg; 25G: min. 22.67, max. 73.31, mean 53.49 ± 13.25 mmHg)
Conclusions:
During a 25 or 23 Gauge PPV, the surgeon must temporally inject a certain amount of PFCL to flatten the retina and perform various maneuvers (laser treatment, membranes peeling, etc.). Since usually the injection is performed manually by a syringe, the pressure at the tip’s is unknown. In our experiments, the IOP measured by the probe in the macular site has been significantly higher than the other two, both in 23 G and in 25 G experiments, suggesting that the direct injection of fluid from the sclerotomy opposite to the macula may add a certain role in a iatrogenic damage. Our study’s outcome has shown very high and unsteady IOP values for manual injection, therefore seems safer to rely on the VFGI control for the PFCL injection
Keywords: 473 computational modeling •
568 intraocular pressure •
764 vitreous substitutes