This invention relates generally to vision protection devices, and more particularly, to a lens system for dentists, surgeons, and other practitioners which system is adapted to provide protection from ultraviolet radiation during surgical and diagnostic procedures.
The retina of the human eye is a thin structure of extreme complexity. The receptors, which may number 125,000,000 in each eye, comprise a large number (about 95%) of rods and a small number (about 5%) of cones. In a rod-free depression of the retina known as the fovea centralis, a small central bouquet of about 2,000 cones are packed together into a hexagonal array having a density of about 150,000 per square millimeter. The cones in this area are capable of dissecting the finest details of the optimal retinal image. The rods and cones are synaptically connected to the bipolar cells, which in turn relate to the ganglion cells, whose axons constitute the optic nerve fibers. There is a high degree of convergence, however, in that the 125,000,000 receptors ultimately feed into only 1,000,000 nerve fibers of the flexible optic nerve, which therefore constitutes the principal bottleneck of information flow in the visual system. The convergence ratio for the fovea is about 1:1, helping to preserve the high detail vision of this region, while in the peripheral region of the retina, the ratio is many thousands to one, leading to high sensitivity at the expense of resolving power.
When the sensory layer of the retina separates from the pigment layer, retinal detachment is said to occur. This may result as a complication of some disease, or may be caused by repeated exposure to ultra violet radiation (light having a wavelength of between 10-380 nm). The detachment is partial at first, but without medical attention, almost always becomes complete, resulting in total and permanent blindness in the affected eye. At first, the patient may "see" flashes of light. Then, the patient may experience the sensation of a curtain gradually moving across the eye. The field of vision becomes progressively cloudy, until vision is lost. The progressive nature of retinal detachment is due to the gradual seepage of fluid from the large vitreous cavity into the space between the two layers of the retina. As more fluid seeps through the original hole in the retina, more of the sensory layer of the retina is separated from the pigment layer, until the detachment is complete.
As indicated above, repeated exposure to ultra-violet radiation can lead to retinal detachment and, if untreated, eventually to blindness. Accordingly, it is important to protect the eyes whenever and wherever exposure to sources of UV radiation is anticipated. Tanning booths, for example, typically provide their patrons with special eye pieces which fit over the eyes and filter out the ultra-violet radiation emitted therein. Because of the intensity of light used in such booths, the eyes of the patron would otherwise be exposed to UV radiation even when closed.
Light sources which emit radiation in the UV range are also utilized in many dental and medical procedures. For example, UV light is typically employed to cure the epoxies or cements used in dental reconstruction or implantation procedures. During surgical or operating room procedures, in which localized, high intensity light is required, a "cold light" source is often employed. Essentially, the cold light source comprises a fiber optic cable which is illuminated by a high intensity high wattage lamp. The light source of the lamp is positioned to illuminate an inlet port of a fiber optic cable, which cable may be a few feet or more in length. The surgeon or dentist uses the fiber optic cable as a light source and he can therefore direct the light emanating from the outlet end of the fiber optic cable to any desired position. Because the amount of light needed for dental as well as surgical procedures is substantial, lamp sources such as halogen, or xenon or other high intensity lamps are employed. Each of these sources emit a sizable power in continuous ultraviolet radiation.
From the foregoing discussion, it can be seen that it in many situations dental or medical practitioners are exposed to significant levels of UV radiation. For this reason, the practitioner must wear glasses or some other visual aid to filter out the harmful radiation. One disadvantage of such visual aids, however, is that they may diminish the clarity or otherwise obscure the practitioner's view of area of the patient under inspection. Accordingly, such aids are often removed when the practitioner desires a clearer view. A further disadvantage of such visual aids is that they do not accommodate the use of magnifying attachments which aid the practitioner in focusing on those areas of particular interest during a given surgical or diagnostic procedure.
Accordingly, it is an object of the present invention to provide a visual aid device for use by dental or medical practitioners which device adequately protects the eyes of the practitioner from the harmful effects of ultraviolet radiation but which also permits the practitioner to obtain an unfiltered view when desired.
It is a further object of the present invention to provide a visual aid which is adapted to incorporate attachments having magnifying or other optical properties so that the device may be employed during typical surgical or diagnostic procedures.