Online optical coherence tomography during subthreshold laser irradiation.

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Laser Medicine

Background:

• Subthreshold laser treatments aim to avoid visible tissue damage.
• Detecting subthreshold lesions is crucial for optimizing treatment efficacy and safety.
• Current methods may not reliably identify minimal laser-induced changes.

Purpose of the Study:

• To evaluate the capability of real-time optical coherence tomography (OCT) in detecting standard and nonvisible subthreshold laser irradiation.
• To assess OCT's utility in identifying laser-induced changes below the threshold of ophthalmoscopic visibility.

Main Methods:

• An integrated system combining a slit-lamp, digital camera, OCT, and a 532-nm laser photocoagulator was utilized.
• Real-time tomographic imaging of the irradiated area was achieved by aligning the laser aiming beam and OCT scan.
• Experiments were conducted on artificial samples (laser testing cards) and biological samples (pig irises).

Main Results:

• Online OCT detected reflectivity profile changes in artificial samples at 200 mW without visible lesions.
• In pig irises, OCT identified changes in optical properties at 860 mW, even without a visible endpoint.
• These findings demonstrate OCT's sensitivity in detecting subthreshold laser effects.

Conclusions:

• Real-time OCT effectively identifies non-ophthalmoscopically visible lesions during subthreshold laser irradiation.
• The study confirms OCT's role in characterizing subtle laser-tissue interactions.
• This technology holds promise for precise monitoring and control of laser therapies.