Research Papers: Therapeutic

Improving the therapeutic window of retinal photocoagulation by spatial and temporal modulation of the laser beam

[+] Author Affiliations
Christopher Sramek

Stanford University, Hansen Experimental Physics Laboratory, 452 Lomita Mall, Stanford, California 94305

Loh-Shan Leung

Stanford University, Department of Ophthalmology, 452 Lomita Mall, Stanford, California 94305

Theodore Leng, Yannis M. Paulus

Eye Institute at Stanford, 2452 Watson Court, Palo Alto, California 94303

Jefferson Brown

Stanford University, Department of Physics, Stanford, California

Georg Schuele

OptiMedica Corp., 3130 Coronado Drive, Santa Clara, California 95054

Daniel Palanker

Stanford University, Hansen Experimental Physics Laboratory, 452 Lomita Mall, Stanford, California 94305

Stanford University, Department of Ophthalmology, 452 Lomita Mall, Stanford, California 94305

J. Biomed. Opt. 16(2), 028004 (February 24, 2011). doi:10.1117/1.3542045
History: Received April 22, 2010; Revised December 21, 2010; Accepted December 27, 2010; Published February 24, 2011; Online February 24, 2011
Text Size: A A A

Decreasing the pulse duration helps confine damage, shorten treatment time, and minimize pain during retinal photocoagulation. However, the safe therapeutic window (TW), the ratio of threshold powers for thermomechanical rupture of Bruch's membrane and mild coagulation, also decreases with shorter exposures. Two potential approaches toward increasing TW are investigated: (a) decreasing the central irradiance of the laser beam and (b) temporally modulating the pulse. An annular beam with adjustable central irradiance was created by coupling a 532-nm laser into a 200-μm core multimode optical fiber at a 4–7 deg angle to normal incidence. Pulse shapes were optimized using a computational model, and a waveform generator was used to drive a PASCAL photocoagulator (532 nm), producing modulated laser pulses. Acute thresholds for mild coagulation and rupture were measured in Dutch-Belted rabbit in vivo with an annular beam (154–163 μm retinal diameter) and modulated pulse (132 μm, uniform irradiance “flat-top” beam) with 2–50 ms pulse durations. Thresholds with conventional constant-power pulse and a flat-top beam were also determined. Both annular beam and modulated pulse provided a 28% increase in TW at 10-ms duration, affording the same TW as 20-ms pulses with conventional parameters.

Figures in this Article
© 2011 Society of Photo-Optical Instrumentation Engineers (SPIE)

Citation

Christopher Sramek ; Loh-Shan Leung ; Theodore Leng ; Jefferson Brown ; Yannis M. Paulus, et al.
"Improving the therapeutic window of retinal photocoagulation by spatial and temporal modulation of the laser beam", J. Biomed. Opt. 16(2), 028004 (February 24, 2011). ; http://dx.doi.org/10.1117/1.3542045


Access This Article
Sign in or Create a personal account to Buy this article ($20 for members, $25 for non-members).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging & repositioning the boxes below.

Related Book Chapters

Topic Collections

Advertisement
  • Don't have an account?
  • Subscribe to the SPIE Digital Library
  • Create a FREE account to sign up for Digital Library content alerts and gain access to institutional subscriptions remotely.
Access This Article
Sign in or Create a personal account to Buy this article ($20 for members, $25 for non-members).
Access This Proceeding
Sign in or Create a personal account to Buy this article ($15 for members, $18 for non-members).
Access This Chapter

Access to SPIE eBooks is limited to subscribing institutions and is not available as part of a personal subscription. Print or electronic versions of individual SPIE books may be purchased via SPIE.org.