Experimental ab interno sclerotomies using a pulsed-dye laser

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Laser Surgery

Background:

• Scleral ablation with visible light lasers is challenging due to low optical absorption, requiring high energies and causing thermal damage.
• Ab interno sclerotomies aim to reduce complications associated with traditional glaucoma surgery by avoiding conjunctival dissection.

Purpose of the Study:

• To evaluate the efficacy and safety of a short-pulse, visible light laser system enhanced with methylene blue dye for creating ab interno sclerotomies.
• To assess thermal damage and complications associated with this novel laser technique in a primate model.

Main Methods:

• A fiberoptic delivery system was used with a flashlamp-pumped dye laser (666 nm) to create ab interno sclerotomies in cynomolgus monkeys.
• Methylene blue dye was applied iontophoretically to enhance scleral optical absorption.
• Postoperative assessment included evaluation of filtration bleb duration and complications.

Main Results:

• Patent sclerotomies were achieved in all 10 monkey eyes using low pulse energies (15-50 mJ/pulse).
• Thermal damage to adjacent sclera was limited to 300 microns.
• Mild hyphema and iridodialysis were observed complications; filtration blebs typically failed within 7 days but were prolonged with 5-fluorouracil treatment.

Conclusions:

• Visible light laser ablation of sclera, enhanced with methylene blue, is effective for creating ab interno sclerotomies with minimal thermal damage.
• This technique offers a less invasive approach to glaucoma surgery, potentially avoiding conjunctival wound issues.
• Further modifications may allow for noninvasive, transcorneal delivery of laser radiation.