In-vitro Retinal Model Reveals a Sharp Transition between Laser Damage Mechanisms
Abstract
We determined laser damage thresholds at 413 nm using a novel environmentally controlled enclosure and a previously described artificially pigmented RPE cell model. Exposure duration ranged from 0.1 to 200 s for a 0.3-mm beam, and 100 to 200 s for a 2.5-mm beam. We found substantial differences between the thresholds for the two beam sizes, which we attribute to a continuing thermal contribution with the larger beam. To better understand the transition from photothermal to photochemical mechanisms, damage from the 0.3-mm beam was assessed with greater temporal resolution between 20 to 100 s. The thresholds for all exposures between 0.1 and 60 s followed the same power function, indicating the same damage rate regardless of mechanism. However, the transition to pure photochemical damage (irradiance reciprocity) was characterized by a sudden 2-fold reduction in threshold value between the exposure durations of 60 and 100 s. Predicted temperature rise data from our thermal model support the theory of a significant thermal component in the damage generated by 60-s exposure. The thermal simulations also support the notion that laser beam diameter, in addition to wavelength and exposure duration, can influence when cells are damaged by purely photochemical means.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 07, 2010
- Accession Number
- ADA523201
Entities
People
- C. D. Clark Iii
- Gary D. Noojin
- Kurt J. Schuster
- Larry E. Estlack
- Michael L. Denton
- Michael S. Foltz
- Robert J. Thomas
Organizations
- Northrop Grumman