Vitreoretinal Surgery with Temperature Management: A Preliminary Study in Rabbits.

The present study aimed to evaluate the structure of the rabbit retina after vitreoretinal surgery using prolonged irrigation with solutions of different temperatures. Thirty-six rabbits (72 eyes) were included in this study and randomly divided into 3 equal groups according to the temperature of the intraocular irrigating fluid they received during vitrectomy. Vitreoretinal surgery was performed with a 5°C irrigation solution in group 1 (12 rabbits, 24 eyes), a 22°C irrigation solution in group 2 (12 rabbits, 24 eyes), and a 36°C irrigation solution in group 3 (12 rabbits, 24 eyes). In each group of animals, the mean irrigation/aspiration time was 30 minutes for left eyes and 60 minutes for right eyes. Histological examination of the retina was performed 1, 7, and 30 days after surgery. During surgery, the temperature in the vitreous cavity of the eyes of rabbits of groups 1, 2, and 3 dropped by 26.0°C, 11.2°C (deep hypothermia), and 1.0°C (mild hypothermia), respectively. The highest rewarming rate was detected in group 1 (0.9°C/min) compared with group 2 (0.7°C/min) and group 3 (0.2°C/min). After 60 minutes of irrigation, retinal structural changes were detected in the animals of groups 1 and 2 (in contrast to the animals of group 3). After surgery with irrigation lasting 30 minutes, no retinal structural changes were observed. This study showed that temperature management, avoidance of intraoperative deep hypothermia, and prevention of rapid uncontrolled rewarming may protect the retinal morphology and increase the safety of prolonged vitreoretinal surgery.

Device Development for Ocular Surface Temperature and Heat Flux Density Measurement.

PURPOSE: Currently, much attention is paid to measuring the temperature of the ocular surface in various ophthalmic diseases. However, for a comprehensive assessment of heat transfer of the eye, it is advisable to measure both the ocular surface temperature and the heat flux (HF) density. This will expand our knowledge of the physiology of the eye and create new possibilities for diagnosing ocular pathology. The present study aimed to develop a thermoelectric device to study rabbits' ocular surface temperature and HF density. METHODS: The multichannel thermoelectric device was developed to measure the ocular surface temperature and HF density. This study included ten rabbits (20 eyes). In all animals, the temperature and the HF density were measured on the surface of the central cornea of both eyes. The measurement was repeated after pupils' dilation. RESULTS: The corneal surface temperature of rabbits was 33.1 ± 0.8 °C, and the HF density of the surface of the cornea was 8.3 ± 0.6 mW/cm2. Our results revealed a high degree of interocular symmetry in the surface HF density in healthy rabbits. After pupil dilation, an increase in the HF density on the surface of the rabbit cornea compared with the initial data and control eye was noted. CONCLUSIONS: The application of the developed device showed that it is safe and allows for the measurement of the ocular surface temperature and the HF density. We believe that further studies on the ocular surface HF density measurement in various eye diseases will allow us to evaluate the possibilities of this device and technique for diagnostic purposes.

Prospects of Temperature Management in Vitreoretinal Surgery.

Currently, there are no clear recommendations about the safety of certain temperature conditions for intraocular structures during vitreoretinal surgery; instructions on the safe rate of rewarming of the vitreous cavity; and the advisability of monitoring ocular temperature in the postoperative period. The purpose was to study the dynamics of epibulbar and intraocular temperature during vitreoretinal surgery. This study included 20 patients with rhegmatogenous retinal detachment (10 eyes) and retinal detachment associated with proliferative diabetic retinopathy (10 eyes). All patients underwent vitreoretinal surgery. In all cases, the ambient temperature, the patient's body temperature, the temperature of the irrigating solution, and temperature in the anterior, mid-, and posterior vitreous were recorded during surgery. Pre- and postoperative thermometry was also performed on the outer ocular surface. During vitreoretinal surgery with room temperature irrigation solution, a decrease in temperature (p < 0.001) versus the initial one was found in all segments of the vitreous cavity. In the absence of continuous irrigation, a rapid rewarming of the vitreous cavity was noted (an average of 0.18°C/min). Our study also demonstrated the presence of regional hyperthermia of the operated eye in a number of patients (25%) in the postoperative period. Current research shows that vitreoretinal surgery is performed under conditions of uncontrolled local ocular hypothermia and is characterized by a rapid uncontrolled rewarming of the vitreous cavity after cessation of cooling, and in the postoperative period local hyperthermia of the operated eye is observed in a number of patients.