A Comparative study of retinal effects from continuous wave and femtosecond mode-locked lasers

✍ Scribed by Robert J. Thomas; Gary D. Noojin; David J. Stolarski; Rebecca T. Hall; Clarence P. Cain; Cynthia A. Toth; Benjamin A. Rockwell

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 367 KB
• Volume: 31
• Category: Article
• ISSN: 0196-8092
• DOI: 10.1002/lsm.10067

✦ Synopsis

Abstract

Background and Objectives

In order to provide a direct comparison of the effects of mode‐locked systems to those with continuous‐wave (CW) or nonpulsed output, we have performed an experiment with lasers possessing otherwise identical output characteristics. This in vivo minimum visible lesion study compares retinal effects of mode‐locked and CW lasers complete with histopathology of the treated areas.

Study Design/Materials and Methods

Titanium:Sapphire lasers produced 800‐nm output for either mode‐locked (76 MHz repetition rate, 120 femtoseconds) or CW exposures. Alternating CW and mode‐locked laser exposures were delivered to the paramacular retinal region of rhesus subjects. Laser exposure duration was set to one‐quarter second for both types of exposures. Through ophthalmoscopic examination of the fundus, a minimal visible lesion (MVL) threshold for damage was established.

Results

Approximately 75 test sites for each type of exposure were examined. The laser dosage thresholds and 95% confidence intervals for minimal visible damage at 24 hours postexposure were found to be 5.9 mJ (5.23–6.6 mJ) and 5.84 mJ (5.23–6.58 mJ) for mode‐locked and CW exposures, respectively.

Conclusions

Results are compared with published studies conducted at similar exposures. These nearly identical damage thresholds indicate a primarily thermal tissue damage mechanism. Comparative histopathology of acute and chronic lesions of both exposure types is also presented. Lasers Surg. Med. 31:9–17, 2002. © 2002 Wiley‐Liss, Inc.