Preliminary animal model experiments have been performed to test the feasibility of a new treatment for snoring. Current surgical treatments for snoring at the palatal level involve either excision of tissue to shorten the palate, or interstitial ablation of the palate to induce fibrosis and stiffening. Both shortening and stiffening of the palate are believed to be effective in reducing snoring. Mucosal surface damage and delayed tissue sloughing are the cause of considerable pain for the patient. In the new treatment proposed here, palatal stiffening with mucosal preservation is accomplished by combining evaporative cooling at the tissue surface with laser irradiation to heat subsurface tissue layers. The surface is cooled using a timed spray of tetrafluoroethane immediately prior to each pulse from a 1.54 micrometer erbium glass laser. In vivo experiments demonstrate that the technique causes significant shrinkage and decreased elasticity in hamster skin, with no tissue sloughing. In vitro experiments with canine soft palates show that laser-induced thermal damage zones ranged from approximately 0.75 to 1.75 mm below the surface, depending on laser parameters. These results suggest that the noninvasive laser technique may produce palatal stiffening with protection of the mucosal surface, for treatment of snoring with minimal morbidity.
A number of recent studies have demonstrated the efficacy of transscleral Nd:YAG and diode cyclophotocoagulation in the reduction of intraocular pressure. The choice of an appropriate wavelength for this treatment modality has been based on a tradeoff of maximal transmission through the superficial layers of conjunctiva and sclera, and maximal absorption in the ciliary body. A UV-Vis-NIR spectrophotometer was used to determine the optical properties of the conjunctiva, sclera, and the ciliary body. These optical properties were used in a Monte Carlo Model to examine the fluence and the resulting rate of heat generation in each layer for the wavelengths of Nd:YAG (1064 nm), semiconductor diode (850 nm), Ruby (693 nm), Krypton yellow (568 nm), and Argon (514 nm) lasers. The results provided a basis for a theoretical prediction of the extent of thermal damage in the ciliary body as a result of transsclerral cyclophotocoagulation. Key Words: transscleral cyclophotocoagulation, Monte Carlo Model, rate of heat generation, Nd:YAG laser, Argon laser, Krypton laser, Ruby laser, semiconductor diode laser.
A number of studies have supported the efficacy of transscleral cyclophotocoagulation in reducing intraocular pressure in human eyes that are refractory to medical or traditional surgical treatments. Due to its recent history, however, no information has yet been made available on optimal exposure parameters for this treatment modality. An 810 nm diode laser was used to examine lesion formation during transscleral irradiation and compared to those reported for the Nd:YAG laser. A large sector iridectomy was performed on the eye, and a slit lamp delivery system combined with a digital image acquisition system (time resolution of 17 milliseconds) were used to view the ciliary body before, during, and after cyclophotocoagulation. The data obtained provide a basis for an in-vivo examination of lesion morphology as well as the underlying mechanism of ciliary destruction using the two laser sources.
The separation of on-axis scattered and unscattered transmission through turbid media has been a difficult experimental task in recent years. This study suggests the use of a polarimeter to filter out the contribution of scattered light to the net on-axis transmission. Red blood cells (RBC) were used to produce the scattering effect. The scattering level was varied by: (1) altering the distance of the detector from the sample, (2) using erythrocytes from three different species, e.g., the dog, goat, and human, which are know to have different RBC sizes, and (3) allowing the RBCs from each species to shrink and swell osmotically. An He-Ne laser was used as the source of the radiation so that data were obtained at a wavelength in the spectral region used in oximetry and hemoglobinometry. In each case, the difference in the scattering cross sections obtained for each sample, with and without polarization filtering, gave us a measure of the filtered scattered light. The results obtained were in close agreement with the expected contribution of scattered radiation to the net axial transmission. This method may be used effectively for all studies involving measurements of on-axis transmission through turbid media, such as biological tissue.