Concepedia

Microphotocoagulation: selective effects of repetitive short laser pulses.

J. Roider, Franz Hillenkamp, Thomas J. Flotte, Reginald Birngruber

Proceedings of the National Academy of Sciences · 1993 · 216 citations · 16 references

Open access

TL;DR

Repetitive exposure to short laser pulses selectively damages absorbing structures at energies below the single‑pulse threshold. The study discusses histological results and the basic mechanism underlying this selective damage. A melanin granule model was developed and applied to explain the observed effects. The findings show additive subthreshold damage that spares adjacent tissues in vivo and selectively damages the retinal pigment epithelium while preserving the neural retina under 514 nm, 5 µs pulses at 500 Hz with 2–10 µJ energy.

Abstract

Repetitive exposure to short laser pulses is shown to cause selective damage to absorbing structures (cells, organelles, or enzymes) with pulse energies below the threshold energy for single-pulse damage. Directly adjacent structures are spared in vivo. Additivity of (presumably nonphotochemical) subthreshold effects is demonstrated. Selective damage to the retinal pigment epithelium with sparing of the neural retina is shown (514 nm, 5 microseconds, 1-500 pulses at 500 Hz, 2- to 10-microJ pulse energy). A melanin granule model has been developed and applied to the experimental situation. Histological results as well as the basic mechanism for these effects are discussed.