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Purpose: Manual, individual adjustment of the laser power in retinal laser therapies is time-consuming, is inaccurate with respect to uniform effects, and can only prevent over- or undertreatment to a limited extent. Automatic closed-loop temperature control allows for similar temperatures at each irradiated spot despite varying absorption. This is of crucial importance for subdamaging hyperthermal treatments with no visible effects and the safety of photocoagulation with short irradiation times. The aim of this work is to perform extensive experiments on porcine eye explants to demonstrate the benefits of automatic control in retinal laser treatments., Methods: To ensure a safe and reliable temperature rise, we utilize a model predictive controller. For model predictive control, the current state and the spot-dependent absorption coefficients are estimated by an extended Kalman filter (EKF). Therein, optoacoustic measurements are used to determine the temperature rise at the irradiated areas in real time. We use fluorescence vitality stains to measure the lesion size and validate the proposed control strategy., Results: By comparing the lesion size with temperature values for cell death, we found that the EKF accurately estimates the peak temperature. Furthermore, the proposed closed-loop control scheme works reliably with regard to similar lesion sizes despite varying absorption with a smaller spread in lesion size compared to open-loop control., Conclusions: Our closed-loop control approach enables a safe subdamaging treatment and lowers the risk for over- and undertreatment for mild coagulations in retinal laser therapies., Translational Relevance: We demonstrate that modern control strategies have the potential to improve retinal laser treatments for several diseases.

Purpose: Subdamaging thermal retinal laser therapy has the potential to induce regenerative stimuli in retinal diseases, but validated dosimetry is missing. Real-time optoacoustic temperature determination and control could close this gap. This study investigates a first in vivo application., Methods: Two iterations of a control module that were optically coupled in between a continuous-wave commercial laser source and a commercial slit lamp were evaluated on chinchilla rabbits. The module allows extraction of the temperature rise in real time and can control the power of the therapy laser such that a predefined temperature rise at the retina is quickly achieved and held constant. Irradiations with aim temperatures from 45°C to 69°C were performed on a diameter of 200 µm and a heating time of 100 ms., Results: We analyzed 424 temperature-guided irradiations in nine eyes of five rabbits. The mean difference between the measured and aim temperature was -0.04°C ± 0.98°C. The following ED50 values for visibility thresholds could be determined: 58.6°C for funduscopic visibility, 57.7°C for fluorescein angiography, and 57.0°C for OCT. In all measurements, the correlation of tissue effect was higher to the temperature than to the average heating laser power used., Conclusions: The system was able to reliably perform temperature-guided irradiations, which allowed for better tissue effect control than simple power control. This approach could enhance the accuracy, safety, and reproducibility of thermal stimulating laser therapy., Translational Relevance: This study is a bridge between preclinical ex vivo experiments and a pilot clinical study.

New procedure of vowel acoustic space (VAS) (of vowel acoustic triangles) transformation for the purpose of characterization of vowel production in individuals with long-term hearing loss (HL) was developed., Objective: To characterize VAS of adult Russian speakers with long-term HL using newly developed acoustic indicators., Material and Methods: Recordings of sustained Russian cardinal vowels /a/, /i/, /u/ of 10 women and 10 men with long-term HL were acoustically analyzed. For each participant, two first formants of each vowel were measured and log-transformed (logF 1 , logF 2 ). VAS was transformed into right triangles, their /u/ corners were moved to the origin, and their legs were aligned with axes. VAS was almost symmetrical, equal and have a maximum size in the control group consisted of subjects without hearing impairment while these of long-term HL group VAS size tended to have reduced and VAS stretched along one axis., Results: Our study showed that a new VAS normalization approach can distinguish at least three groups of people with long-term HL., Conclusion: There are those with vowel triangles stretched along logF 1 -axis, with vowel triangles stretched along logF 2 -axis, and with symmetrical vowel triangles. Causes of the VAS differences require further investigation.