Thermodynamics of vitreoretinal surgery.

PURPOSE: To report in vivo the temperature variations occurring continuously inside the human eye during vitreoretinal surgery.
METHODS: Intraocular temperature was monitored during the entire surgical time in 14 eyes of 14 patients undergoing pars plana vitrectomy. A custom made 23-gauge thermoprobe was inserted through a sclerotomy at 3.5 mm from the limbus. Temperature in the anterior chamber and on the retinal surface was measured at one time point, whilst the temperature in the vitreous cavity was monitored throughout the entire surgery. Time points of particular interest in the vitreous cavity were: at baseline (inflow off - outflow off), at the beginning of the vitrectomy (inflow off - outflow on), at the end of vitrectomy (inflow on-outflow on), during the epiretinal procedures (inflow on-outflow off), under air infusion, under oil and under endolaser treatment ongoing.
RESULTS: The mean temperature in the anterior chamber and on the nasal retinal side was 23.6 °C (SD 1.8)and 32.3 °C (SD 1.1), respectively. The mean vitreous temperature at baseline, before opening the infusion, was 33.6 °C (SD 1.4). The mean temperature at the beginning and the end of the vitrectomy was 26.8 °C (SD 1.0) and 24.8 °C (SD 0.8), respectively. During the epiretinal procedures, the mean temperature was 27.4 °C (SD 0.7). Under air infusion, the mean temperature increased to 29.2 °C (SD 1.2). The fluctuations in temperature were statistically different between the time points during the vitrectomy (p < 0.001).
CONCLUSION: Vitreoretinal surgery induces measurable changes in temperature in the human eye, with significant fluctuations. In particular, the temperature in the vitreous cavity decreases when both the inflow and the outflow fluid lines are open, whilst it increases under air infusion.