Corneal Damage from Mid-Infrared Laser Radiation
Abstract
Corneal epithelial damage thresholds for exposures to sequences of pulses of 1.55 jim infrared radiation produced by an Er fiber laser were investigated. Thresholds were determined for sequences of 8 to 128 pulses at a repetition frequency of 10 Hz and 8 to 256 pulses at 20 Hz. The duration of the individual pulses was 0.025 sec and the 1/e diameter of the laser beam was 0.1 cm. Threshold damage is correlated by an empirical power law of the form H(sub th) = CN(exp -a), in which H(sub th) is the threshold radiant exposure per pulse, and N is the number of pulses. The value of the exponent a is 0.32 for the 10 Hz exposures and 0.34 for the 20 Hz exposures. The constant C is 7.60 for the 10 Hz exposures and 5.99 for the 20 Hz exposures. Both values are greater than the estimated threshold for a single 0.025 sec pulse (4.90 J/sq cm). Thus the empirical power law breaks down for small numbers of pulses (viz., N < 8) where it overestimates the damage thresholds. An empirical critical temperature model also correlates the multiple-pulse injury thresholds.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2004
- Accession Number
- ADA426132
Entities
People
- Russell L. Mccally
Organizations
- Johns Hopkins University