The Effect of Altitude in the Intraocular Pressure After Pars Plana Vitrectomy and Intraocular Sulfur Hexafluoride (SF6) in Rabbits

Abstract

Abstract: : Purpose: To determine the behavior of intraocular pressure in eyes undergoing pars plana vitrectomy and sulfur hexafluoride at different filled levels of vitreous cavity, modifying the altitude during a ground travel. Methods: Five rabbits eyes undergoing vitrectomy, 3 with a filled % of vitreous cavity of 25%, 50% and 100%, the forth with balanced solution 100% (control) and the fifth with air 100%. A sixth no vitrectomized rabbit with a bubble of 0.35 cc simulated a pneumoretinopexia. A masked investigator determined basal IOP at Mexico city level (2260 mts) and checked it every 300 mts of ascending and descending in the way to Puebla city. Rabbit scleral rigidity with Friedenwald nomogram was calculated. Results: Total ascending from basal: 949mts. (Max. reached altitude: 3209mts), significant differences were noted in those with filled % vitreous cavity of 100%, 50%, 25% gas and 100% air. We could determine for each 100 mts of elevation an IOP rising of 1.53, 1.046, 0.971 and 0.970 respectively. There was no variation of IOP in eyes with solution and pneumoretinopexia. No significant difference in scleral rabbit and human rigidity was found. Conclusions: Altitude strongly influences the IOP in eyes with SF6 filled vitreous cavity at 100%, 50%, 25% and air 100%. Scleral rigidity, the kind of gas and the filled percentage of vitreous cavity are important factors when advicing traveler patients in the immediate postoperative time.

Keywords: retinal detachment • intraocular pressure • vitreous substitutes