University of Lübeck, Institute of Biomedical Optics, Lübeck, Germany.
J Biomed Opt. 2012 Jun;17(6):061219. doi: 10.1117/1.JBO.17.6.061219.
The induced thermal damage in retinal photocoagulation depends on the temperature increase and the time of irradiation. The temperature rise is unknown due to intraocular variations in light transmission, scattering and grade of absorption in the retinal pigment epithelium (RPE) and the choroid. Thus, in clinical practice, often stronger and deeper coagulations are applied than therapeutically needed, which can lead to extended neuroretinal damage and strong pain perception. This work focuses on an optoacoustic (OA) method to determine the temperature rise in real-time during photocoagulation by repetitively exciting thermoelastic pressure transients with nanosecond probe laser pulses, which are simultaneously applied to the treatment radiation. The temperature-dependent pressure amplitudes are non-invasively detected at the cornea with an ultrasonic transducer embedded in the contact lens. During clinical treatment, temperature courses as predicted by heat diffusion theory are observed in most cases. For laser spot diameters of 100 and 300 μm, and irradiation times of 100 and 200 ms, respectively, peak temperatures range between 70°C and 85°C for mild coagulations. The obtained data look very promising for the realization of a feedback-controlled treatment, which automatically generates preselected and reproducible coagulation strengths, unburdens the ophthalmologist from manual laser dosage, and minimizes adverse effects and pain for the patient.
视网膜光凝术引起的热损伤取决于温度升高和辐照时间。由于眼内光传输、散射和视网膜色素上皮 (RPE) 和脉络膜的吸收程度的变化，温度升高是未知的。因此，在临床实践中，经常应用比治疗所需更强和更深的凝固，这可能导致神经视网膜损伤和强烈的疼痛感知。这项工作侧重于光声 (OA) 方法，通过重复用纳秒探测激光脉冲激发热弹压力瞬变来实时确定光凝过程中的温升，同时将这些激光脉冲应用于治疗辐射。在角膜处用嵌入接触镜中的超声换能器非侵入性地检测与温度相关的压力幅度。在临床治疗中，在大多数情况下观察到热扩散理论预测的温度曲线。对于直径为 100 和 300 μm 的激光光斑，以及分别为 100 和 200 ms 的辐照时间，温和凝固的峰值温度范围在 70°C 至 85°C 之间。所获得的数据对于实现反馈控制治疗非常有前景，该治疗可以自动生成预选的和可重复的凝固强度，使眼科医生无需手动进行激光剂量控制，并最大程度地减少患者的不良反应和疼痛。
