Effects of the CW YAG Laser on the Human Iris and Retina

Lasers in ophthalmology

This article reviews the principle uses of ophthalmic lasers, providing historical background with an emphasis on new applications and areas of investigation. Ophthalmic photocoagulation was the first medical laser application and has restored or maintained vision in millions of people. More recently, photodisruption and, increasingly, ablation have gained prominence for treating a wide range of ocular pathology. The unique properties of lasers have also been harnessed for diagnostic purposes, with optical coherence tomography representing a significant improvement over existing imaging methods. Many ophthalmic applications of lasers have been developed, but the field is a dynamic one which continues to evolve along with laser technology itself.

A study of the mechanism of ocular irritation following YAG laser capsulotomy in rabbits

The irritative response to Nd:YAG laser capsulotomy was studied in unanaesthetized rabbits. Posterior lens capsulotomy with a total energy of 100 mJ had no effect on the pupil size but increased the intraocular pressure by 5-10 mmHg and caused a breakdown of the blood-aqueous barrier. Anterior lens capsulotomy with a total energy of 20, 60 or 100 mJ caused constriction of the pupil, and an increase in intraocular pressure in a dose-dependent manner, and a breakdown of the blood-aqueous barrier. Indomethacin attenuated all the component parts of the irritative response and (D-arg1, D-pro2, D-trp7,9, leu11)-SP attenuated the miotic response. A combination of indomethacin and the substance P antagonist almost completely abolished the irritative response. This indicates that the acute YAG-laser-induced irritation in the rabbit eye is dependent both on a release of prostaglandins and on substance P, the former probably releasing the latter from sensory nerves.

Wavelength selection in macular photocoagulation. Tissue optics, thermal effects, and laser systems

The therapeutic effects of macular photocoagulation result from focal heating of the retina and choroid. The magnitude, spatial extent, and duration of temperature increases produced by laser exposures are influenced by light scattering in intraocular and intraretinal transit; light absorption by melanin, hemoglobin, and xanthophyll in target tissues; and beam parameters, such as wavelength, spot size, and exposure duration. Tissue optics and thermodynamics provide a useful guide for selecting new laser systems of potential value in macular photocoagulation, but laser-tissue interactions and subsequent chorioretinal responses are poorly understood, and therapeutic efficacy can be established only by controlled clinical trials.

Histology of macular photocoagulation

The histology of macular photocoagulation is reviewed. This information may be helpful in selecting the best available laser for retinal vascular and choroidal disorders in the macular region, as providing an experimental method to better understand the effects of photocoagulation on retinal disease processes.