Sliney, David H.; (1991) Interaction mechanism of short-pulse laser radiation with ocular tissues and their clinical implications. Doctoral thesis (Ph.D.), University College London.

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Abstract

Traditional laser photocoagulation of the retina requires CW exposures of the order of 0.1 s. An extensive literature exists on thermal damage mechanisms and biological sequellae of coagulation. By contrast, the biophysical mechanisms of pulsed laser interactions are poorly uiiderstood. The use of photodisruption and photoablation by submicrosecond laser pulses to cut tissue has recently gained considerable clinical attention. In addition, selective photocoagulation of localized target tissue would also require short-duration pulses. The biophysical mechanisms of short-pulse laser interaction with tissue will influence the surgical outcome. Without a full understanding of these mechanisms, the new and the potential ophthalmic applications of pulsed lasers cannot be optimised, nor can one accurately predict potential delayed effects. The aim of the research reported in this thesis has been first to study the biophysical mechanisms in a series of experiments and then to consider how to optimise laser exposure parameters in relation to the desired surgical effect while minimizing undesirable collateral effects. Focal laser interaction with target tissue may produce adverse effects to non-target tissues from photochemical, thermal and acoustical phenomena. Acoustical, mechanical impulse, and other phenomena which differ between mode-locked and Q-switched exposures were investigated. Optical breakdown, thermo-acoustic effects, photochemical ablation, thermal vaporization and selective photothermal coagulation are all considered.

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