Micropulse and continuous wave diode retinal photocoagulation: visible and subvisible lesion parameters

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Laser Medicine

Background:

• Subvisible micropulse diode laser photocoagulation limits heat conduction for precise retinal damage localization.
• Treatment power is often based on continuous wave lesion thresholds.
• Understanding power requirements for visible micropulse vs. continuous wave lesions is key.

Purpose of the Study:

• To measure and compare the clinical laser powers needed for visible endpoint micropulse and continuous wave diode laser retinal photocoagulation.
• To evaluate the safety margins of these laser modalities in retinal treatments.

Main Methods:

• Diode laser (810 nm) burns were created in the peripheral retina of diabetic retinopathy patients.
• Minimal powers for visible continuous wave and micropulse lesions were determined.
• Fluorescein angiography and fundus photography assessed lesion appearance; MPE levels were calculated.

Main Results:

• Visible micropulse lesions required 1800 mW (54 mJ), while continuous wave lesions needed 300 mW (60 mJ).
• Lesions exceeded maximal permissible exposure (MPE) levels by 133x (micropulse) and 36x (continuous wave).
• Laser energies were comparable between continuous wave and micropulse visible lesions.

Conclusions:

• Visible micropulse lesions necessitate 6x more power but similar energy compared to continuous wave lesions.
• No significant difference in minimal power for angiographically apparent micropulse lesions was found.
• The safety margin was 3.7x greater for micropulse diode laser photocoagulation than for continuous wave.