Advantages:

Modulation of variations in temperature occurring inside the human eye during vitreoretinal surgery and of effects of such variations in temperature on intraocular tamponades.

Methods:

Intraocular temperature was monitored during the entire surgical time in 16 eyes of 16 patients undergoing pars plana vitrectomy. A custom made 25 gauge thermoprobe was inserted through a trocar access at 3.5 mm from the limbus. Temperature in the anterior chamber and on the retinal surface was measured at one time point, while temperature in the vitreous cavity was monitored during the entire surgery. Time points of particular interest were: at baseline (inflow off – outflow off), at the beginning of the vitrectomy, at the end of vitrectomy (inflow on – outflow on), during the epiretinal procedures (inflow on – outflow off) and under air infusion. The effect of the recorded temperature variations on intraocular tamponades (at low and high density) was investigated in vitro using an eye chamber with saccadic simulator.

Effectiveness / Safety:

The Fluctuation in temperature during the vitrectomy induces apoptosis, inflammation and retinal damage. Moreover the variations in temperature determined a significant increase in shear viscosity, emulsion and opalescence of the intraocular tamponade. This is due to a temperature-dependent change in the saturation point.

Results:

The mean temperature in the anterior chamber and the retina was respectively 23.6 (SD 1.4) °C and 28.8 (SD 1.5) °C. (P= 0.002) The average temperature in vitreous cavity during the entire procedure was 27.3 (SD 2.1) °C. The mean vitreous temperature at baseline, before opening the infusion, was 27.1 (SD 1.8) °C. At the beginning and at the end of the vitrectomy, the mean temperature was respectively 28.7 °C (SD 2.8) and 24.7 (SD 1.5) °C (P=0.015). During the epiretinal procedures the mean temperature was 28.1 (SD 2) °C. Under air infusion, the mean temperature increased to 29.50 °C (P=0.03).

Take Home Message:

Vitreoretinal surgery induces measurable changes in temperature in the human eye. In particular, the temperature in the vitreous cavity decreases when both the inflow and the outflow fluid lines are open, and under air infusion. The interactions between PFCL–HSO is temperature dependent and lead to the formation of hyperviscous solutions that could be described as “sticky oil”. The modulation of temperature during the vitreoretinal surgery is helpful to prevent iatrogenic retinal damage and to change the shear viscosity and vapor tension of intraocular tamponade.