Comprehensive Detection, Grading, and Growth Behavior Evaluation of Subthreshold and Low Intensity Photocoagulation Lesions by Optical Coherence Tomographic and Infrared Image Analysis

Abstract

Purpose. To correlate the long-term clinical effect of photocoagulation lesions after 6 months, as measured by their retinal damage size, to exposure parameters. We used optical coherence tomographic (OCT)-based lesion classes in order to detect and assess clinically invisible and mild lesions. Methods. In this prospective study, 488 photocoagulation lesions were imaged in 20 patients. We varied irradiation diameters (100/300 µm), exposure-times (20–200 ms), and power. Intensities were classified in OCT images after one hour, and we evaluated OCT and infrared (IR) images over six months after exposure. Results. For six consecutive OCT-based lesion classes, the following parameters increased with the class: ophthalmoscopic, OCT and IR visibility rate, fundus and OCT diameter, and IR area, but not irradiation power. OCT diameters correlated with exposure-time, irradiation diameter, and OCT class. OCT classes discriminated the largest bandwidth of OCT diameters. Conclusion. OCT classes represent objective and valid endpoints of photocoagulation intensity even for “subthreshold” intensities. They are suitable to calculate the treated retinal area. As the area is critical for treatment efficacy, OCT classes are useful to define treatment intensity, calculate necessary lesion numbers, and universally categorize lesions in clinical studies.

Lesion strength control by automatic temperature guided retinal photocoagulation

“…The classes can also be used to improve the characteristic damage threshold algorithms and enable subvisible thermal laser treatment of the retina with a temperature based and, thus, objectively defined dosage. 27,28 Clinical studies are necessary in . This is an aberration from the goal to achieve lesions of uniform size.…”

In vivo early retinal structural alterations following laser photocoagulation using three-dimensional spectral domain optical coherence tomography

“…These changes, however, may show a temporal delay. The retinal structural changes may not be visible on early OCT images, but are visible on the follow-up images 9. Koinzer et al have documented an OCT-based classification of laser-induced retinal morphological changes.…”

Retinal Laser Lesion Visibility in Simultaneous Ultra-High Axial Resolution Optical Coherence Tomography

“…In their recent study, Koinzer at al. [2] reported first detectable changes 2h after treatment with an increased scattering to be located in the neuronal retina. However, when applying lasers for retinal treatment, the melanin in the RPE acts as the main absorber of commonly used treatment lasers emitting in the green and yellow spectral range [5], [6].…”

“…Thus, an ophthalmoscopic assessment of the laser coagulation effects in deeper retinal layers is not possible. Recent studies by Koinzer et al [2] have shown that ophthalmoscopic analysis of laser coagulation burns may be misleading regarding effective laser lesion size and total affected tissue area.…”