Investigating the ocular temperature rise during femtosecond laser lens fragmentation: an in vitro study

Purpose: To investigate the trend of temperature variation during lens fragmentation simulated by a femtosecond laser on an in vitro eye model. Methods: In our experimental study, a convex cylinder of gelatinous material, usually employed in femtosecond laser calibration, was used to simulate both an anterior segment and a crystalline lens during fragmentation performed with the Victus femtosecond laser (Technolas Perfect Vision GmbH, Germany; Bausch + Lomb Incorporated, USA). Two radiated energies (7000 nJ and 9000 nJ) and three cutting patterns (crosses, circles and cross + circle) were applied. Trends of temperature variation as a function of time were obtained using a T-type thermocouple. Results: The maximum value of temperature rise during lens fragmentation ranged from 3.53 to 5.13 degrees; the rise was directly proportional to the intensity of the radiated energy (7000 nJ or 9000 nJ) and the cutting pattern performed. This behavior was experimentally represented by an asymmetric function with a characteristic bell curve shape, whereas it was mathematically described by a transport diffusive model. Conclusions: Since the temperature rise at the fragmentation volume base resulted to be around 5 degrees in our in vitro study, lens fragmentation performed using the Victus femtosecond laser might be considered safe form a thermal point of view.