Cumulative Thermal Accumulation in Transscleral Cyclophotocoagulation: Mathematical Modeling of Controlled Versus Destructive Thermal Effects in Secondary Neovascular Glaucoma

Source abstract

Purpose. To quantitatively characterize the cumulative thermal dynamics of ciliary body tissue during serial transscleral cyclophotocoagulation and to evaluate the potential applicability of the thermal accumulation index (TAI) as a tool for predicting controlled coagulative and potentially destructive thermal effects in secondary neovascular glaucoma. Methods. Stepwise mathematical modeling of serial transscleral cyclophotocoagulation (20 applications of 2 s with 1 s inter-application intervals) was performed. For each cycle, initial tissue temperature (Tstart), maximum temperature (Tmax), temperature rise (ΔT), and inter-application heat loss (HeatLoss) were determined. Total time within coagulative (50–60 °C) and destructive (>60 °C) temperature ranges, as well as the area under the temperature curve within the coagulative range (AUTC), were assessed. The thermal accumulation index (TAI) was calculated as the mean increase of the initial temperature above the baseline level of 37 °C. Additional threshold and scenario analyses were performed by varying laser exposure parameters. Results. Serial laser exposure produced cumulative thermal dynamics characterized by gradual elevation of baseline tissue temperature from 37.0 °C to 42.7 °C. The cumulative temperature increase reached 57.0 °C, corresponding to TAI = 2.85 °C and indicating controlled thermal accumulation without transition to the destructive temperature range. Analysis of thermal profiles demonstrated that shorter inter-application intervals or higher energy delivery enhanced thermal accumulation. Within the mathematical model, TAI values exceeding 4.0 °C were associated with an increased risk of tissue overheating and transition to the destructive temperature range (>60 °C). Under simulated conditions, the continuous-wave 1 W mode corresponded to a profile of controlled low-power coagulation. Conclusions. Cumulative thermal accumulation represents an important component of tissue temperature response during serial TSCPC and is determined by incomplete cooling between consecutive applications. The proposed TAI enables quantitative characterization of inter-application heat accumulation and may be considered an integral indicator of cumulative thermal dynamics under different laser exposure regimes. Under simulated conditions, the low-power continuous-wave 1 W mode provided a controlled coagulative effect without transition to the destructive temperature range, consistent with the low-dose / slow coagulation concept. The obtained findings are model-based and require further experimental and clinical validation.