Spraul C. W.

Department of Ophthalmology, University of ULM, Germany

Background: Clinical therapeutic use of photocoagulation began with the pioneering work of Meyer-Schwickerath at the University of Hamburg. It was not until 1960 that Theodore Maiman built the first successful laser with a ruby crystal medium. Since that time laser technology has a unprecedented success story in ophthalmology.
Methods: Laser-tissue-interaction can be classified into at least four categories, i.e. thermal effects (photocoagulation), photochemical effects (photoablation), mechanical effects (photodisruption), and evaporation effects.
Results: Histologic examination of effects of argon laser coagulation display varying structural changes depending on the laser energy and pigmentation of the retinal pigment epithelium, i.e. the density of melanin and melanolipofuscin pigments in these cells. Histologic studies of corneas following excimer laser treatment have shown no significant zone of thermal necrosis. This has been termed "ablative photodecomposition"; i.e. molecules on the irradiated surface are broken into small volatile fragments. With photodisruption microplasma temperature reaches 15000 °C focally. Vaporisation and melting of liquids and solids occur in a small volume near the focal point and clinically photocoagulation is not important.
Conclusion: Ophthalmic laser therapeutics are continuously expanding through the synergy of advances in the scientific discipline of photobiology, photohistology including ultrastructural examination, developing laser technology, and increasingly precise delineation of clinical requirements by ophthalmic laser surgeons.

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