Abstract:
This disclosure relates to the application of a photoluminescent material with a plurality of nanocrystals, such as quantum dots or Cornell dots, each capable of absorbing electromagnetic energy at a first wavelength and emitting the absorbed energy as a desired wavelength in the direction of a human retina. Preferably, the emitted wavelength is chosen for its ability to suppress naturally occurring melatonin, i.e., blue light. The disclosure also contemplates the placement of the photoluminescent material over the entire surface of a lens or on a portion of the lens to optimize the exposure to the desired wavelength while reducing the overall luminescence. Finally, the photoluminescent material can be applied as a coating, as part of a material applied to the lens, either superficially or in/within the lens, as part of eyewear, or even as an optical treatment system.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present patent application claims priority from and the benefit of U.S. Provisional Patent Application No. 61/026,905, filed Feb. 7, 2008, and entitled Light Wavelength Conditioning Optical Device, which prior application is incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates to a retinal melatonin suppressor, eyewear, an optical treatment system capable of suppressing melatonin found in the retina, and a coating capable of giving a lens on which the coating is applied retinal melatonin suppression properties. More specifically, this disclosure relates to the use of photoluminescent material with nanocrystals capable of emitting desirable light at specific wavelengths in the direction of the retina. 
     BACKGROUND 
     Darwinian theory states that humans evolved on Earth and are consequently adapted to interact with their environment. For example, when exposed to sunlight, human skin synthesizes vitamin D, a useful vitamin. The use of blue light (i.e., the color of the sky), when used in conjunction with an aminolevulinic acid treatment, is documented to improve porphyrin response times in skin. 
     The human eye is another organ known to react to environmental factors. Phototherapy, or the science of exposing the body to a spectrum of light for therapeutic purposes, is known or believed to be effective in treating Seasonal Affective Disorder, nonseasonal depressions, and delayed sleep phase syndrome when specific types of light are received by the human eye. 
     The first generation of light therapy devices produced a white light across the spectrum of wavelength, often requiring a source to illuminate at levels of up to 10,000 lux. Such intense light includes ultraviolet and infrared light that can be harmful to the human eye at intense levels. The benefit from these devices is cancelled by these adverse health benefits associated with intense levels of exposure. 
     Modern studies reveal that certain specific wavelengths of light, often in the blue spectrum ranging from 420 to 485 nm, are most effective in the treatment of Seasonal Affective Disorder and other psychiatric conditions. These benefits have been linked with the capacity of blue light to suppress the naturally present melatonin in the human retina, and more specifically, to interact with the melatonin receptor 1B (MT2 subtype). Melatonin is a primary hormone secreted by the pineal gland. Other research has shown a greater proportion of melatonin in the inferior and/or nasal portion of the retina. 
     Existing cosmetic devices that seek to expose individuals to light at wavelengths in the blue spectrum are bulky and difficult to manage. In addition, such devices require a power source and are otherwise difficult or impossible to use in a mainstream consumer application. An example of a prior art device is shown in  FIG. 1 . A selective color filter is placed between a nonportable source of light and a user of the device. Since the effective dose is measured as the incoming flux of radiation multiplied by the exposure time to the radiation, for a constant dose, the time of exposure can only be reduced if the intensity of the light is increased. As a consequence, the benefits of high-intensity light, even in the blue spectrum, is offset by the potential health hazards from intense light exposure. 
     In addition, most existing light therapy devices make use of an electric power source to generate light. Some models of light enhancement devices include eyewear with battery-powered light emitting diodes (LEDs) or other light sources. An example of this prior art device is shown in  FIG. 2 . Glasses equipped with bulky equipment are uncomfortable to wear and require frequent regeneration of the power source. While these devices convey the benefits of light therapy in the strictest sense, they do not address the real challenges inherent with the cosmetic and practicality concerns of the wearer. 
     Yet another type of prior art sunglasses used for light therapy does not use a power source but simply filters and attenuates incoming ambient photons at sunlight spectrum wavelengths. This technology makes use of a filter or a plurality of filters to eliminate or otherwise attenuate part of the incoming light spectrum (often, any non-beneficial wavelengths) from passing through the medium. In short, such technology is subtractive only and does not enhance beneficial wavelengths. 
     Finally, another type of prior art uses chemically fluorescent material to enhance the sensation of certain specific colors in the visible spectrum by use of a fluorescent dye. As a consequence of dyeing the lens, other colors in the visible radiation spectrum decrease in intensity. A contrast is created and some colors that cannot be perceived by color challenged individuals, for example blue, appear brighter. This system does not increase the incoming flux of any single color; it merely segregates a problematic spectrum from the overall spectrum to facilitate differential perception. 
     It would therefore be advantageous to provide a cosmetically acceptable, wearable device that increases the exposure of all or part of the human retina to beneficial wavelengths of light without requiring the use of bulky devices, power sources, or high-intensity fluxes. In particular, it would be advantageous to provide a solution that can be both subtractive and additive-converting nontherapeutic (or possibly even harmful) wavelengths into therapeutic, beneficial, or at the very least, nonharmful wavelengths. 
     SUMMARY 
     This disclosure relates to the application to an optical device of a photoluminescent material with a plurality of nanocrystals, such as quantum dots or other fluorescent nanoparticles, each capable of absorbing photons at a first (potentially undesirable) wavelength and emitting the absorbed energy at a second, desired wavelength. By directing, for example, emitted blue light in the direction of a human retina, naturally occurring melatonin may be suppressed. The disclosure also contemplates the placement of nanocrystals over the entire surface of a lens or a portion of a lens to optimize the melatonin exposition to the desired wavelength while reducing overall luminescence. Finally, nanocrystals can be applied as a coating, as part of a material applied to the lens, either superficially or within the lens, as part of eyewear, or even as an optical treatment system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments are shown in the drawings. However, it is understood that the present disclosure is not limited to the arrangements and instrumentality shown in the attached drawings. 
         FIG. 1  is a figurative illustration of a nonportable light therapy device from the prior art. 
         FIG. 2  is a figurative illustration of a portable light therapy device from the prior art. 
         FIG. 3  is a diagrammatical representation of nanocrystals according to an embodiment of the present disclosure. 
         FIG. 4  is a graphical representation of the absorption and emission profiles of three different examples of nanocrystals as shown in  FIG. 3  according to an embodiment of the present disclosure. 
         FIG. 5A  is a perspective view of eyewear equipped with optical lenses where substantially all of at least one lens includes a photoluminescent material according to an embodiment of the present disclosure. 
         FIG. 5B  is a cross-sectional view along line  5 B-E as shown in  FIG. 5A  where the substrate uniformly includes the photoluminescent material. 
         FIG. 5C  is a cross-sectional view along line  5 B-E as shown in  FIG. 5A  where a layer of photoluminescent material is located on an external surface of the substrate. 
         FIG. 5D  is a cross-sectional view along line  5 B-E as shown in  FIG. 5A  where a layer of photoluminescent material is located on both an internal and external surface of the substrate. 
         FIG. 5E  is a cross-sectional view along line  5 B-E as shown in  FIG. 5A  where two layers of photoluminescent material are sandwiched in the substrate. 
         FIG. 6A  is a perspective view of eyewear equipped with optical lenses where only a portion of at least one lens includes photoluminescent material according to another embodiment of the present disclosure. 
         FIG. 6B  is a cross-sectional view along line  6 B-E as shown in  FIG. 6A  where the portion of the substrate uniformly includes the photoluminescent material. 
         FIG. 6C  is a cross-sectional view along line  6 B-E as shown in  FIG. 6A  where a layer of photoluminescent material is located on an external surface of the substrate. 
         FIG. 6D  is a cross-sectional view along line  6 B-E as shown in  FIG. 6A  where a layer of photoluminescent material is located on both an internal and external surface of the substrate. 
         FIG. 6E  is a cross-sectional view along line  6 B-E as shown in  FIG. 6A  where two layers of photoluminescent material are sandwiched in the substrate. 
         FIG. 7A  is perspective view of eyewear equipped with optical lenses where another portion of at least one lens includes photoluminescent material according to yet another embodiment of the present disclosure. 
         FIG. 7B  is a cross-sectional view along line  7 B-E as shown in  FIG. 7A  where the other portion of the substrate uniformly includes the photoluminescent material. 
         FIG. 7C  is a cross-sectional view along line  7 B -E as shown in  FIG. 7A  where a layer of photoluminescent material is located on an external surface of the substrate. 
         FIG. 7D  is a cross-sectional view along line  7 B -E as shown in  FIG. 7A  where a layer of photoluminescent material is located on both an internal and external surface of the substrate. 
         FIG. 7E  is a cross-sectional view along line  7 B-E as shown in  FIG. 7A  where two layers of photoluminescent material are sandwiched in the substrate. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting and understanding the principles disclosed herein, reference is now made to the preferred embodiments illustrated in the drawings, and specific language is used to describe the same. It is nevertheless understood that no limitation of the scope of the invention is hereby intended. Such alterations and further modifications of the illustrated devices and such further applications of the principles disclosed and illustrated herein are contemplated as would normally occur to one skilled in the art to which this disclosure relates. 
     Certain materials have the property of being able to receive and absorb, at least temporarily, electromagnetic energy at a first profile of wavelengths or bands of wavelengths and to emit the electromagnetic energy at a second, different profile of wavelengths or bands of wavelengths. Dyes having fluorescence properties, such as known organic compounds, emit light close to or about the same wavelength as the light that has been absorbed. The emission profile of the light remains within 20 to 30 nm of the absorption profile. For example, some fluorescent dyes absorb red light and emit light somewhat shifted in the red direction. As a consequence, there can be no significant enhancement of any color of light because the absorbed light corresponds to the emitted light. 
     Nanocrystals differs greatly from fluorescent dyes in their absorption and emission profiles.  FIG. 4  shows the difference between the absorption and emission profiles for three different types of nanocrystals. Absorbed light is stored from significantly lower wavelengths and emitted at very narrow bands—a red-emitting nanocrystal does not absorb red light, and as a consequence, light enhancement at a specific wavelength is possible. 
       FIG. 4  shows three possible photoluminescent materials with nanocrystals, such as so-called quantum dots as shown in  FIG. 3 , having different absorption and emission profiles for the visual spectrum of wavelengths. As known in the art, quantum dots, such as those manufactured by Invitrogen Corporation and shown in  FIG. 3 , may comprise a small core  1  of a semiconductor material such as cadmium with selenium or tellurium within an outer shell  2  also of a semiconductor material such as zinc sulfide coated, that is itself surrounded with a suitable polymer  3  such as polyethylene glycol (PEG). The emission color a quantum dot is a function of its size, which typically ranges from 10 to 20 nm in diameter. In a similar vein, so-called “Cornell Dots” may also be employed. As described in U.S. Patent Application Publication Nos. 2004/0101822 (published May 27, 2004) and 2006/0183246 (published Aug. 17, 2006), the entirety of which are incorporated herein by this reference, Cornell Dots comprise a similar core and shell arrangement as quantum dots on the same dimensional scale, but in which the core comprises a few molecules of fluorescent dye surrounded by a silica shell without the additional polymer coating. 
     In  FIG. 4 , lines  10   a , and  10   b  respectively illustrate the photoluminescent absorption and emission profiles for the black Qdot® nanocrystal from the Invitrogen Corporation, which appears black because it emits light at a wavelength of about 800 nm. Lines  11   a , and  11   b  respectively illustrate the photoluminescent absorption and emission profiles for the orange Qdot® nanocrystal from Invitrogen Corporation, which appears orange because it emits light at a wavelength of about 605 nm. Finally, lines  12   a , and  12   b  respectively illustrate the photoluminescent absorption and emission profiles for the blue Qdot® nanocrystal from Invitrogen Corporation, which appears blue because it emits light at a wavelength of about 525 nm. In a presently preferred embodiment, photoluminescent materials (such as nanocrystals) that emit substantially light tending toward the blue portion of the visible spectrum are employed. 
       FIG. 4  illustrates how shorter wavelengths shown to the left of the figure are absorbed and then emitted at a different, longer wavelength. While one type and model of nanocrystals using quantum dot technology is shown and disclosed, the use of any type of nanocrystals capable of absorption at one portion of the wavelength spectrum and the release of energy at a selected visible wavelength such as, for example, blue, is contemplated. 
     As noted above, blue light at specific wavelengths has been found useful in treating Seasonal Affective Disorder at low-intensity exposure. Light, often quantified as “blue light” having a wavelength ranging between 460 to 485 nm, may be efficient in treating photosensitive pigments with a peak sensitivity of about 479 nm. While a preferred embodiment with the emission of photons as between 420 to 485 nm is disclosed, emission at other wavelengths in the visible, near visible, or invisible spectrum is also contemplated. 
     For example, in one embodiment, invisible ultraviolet (UV) wavelengths are converted into visible blue or green wavelengths. Of course, other wavelength conversion may be possible based on the type and/or capabilities of the particular photoluminescent (or conversion) material used. More particularly, quantum or Cornell dots are added to optical devices, such as lenses, during manufacturing. Such lenses may be incorporated into eyewear, which may in turn be incorporated into a treatment systems, as described below. 
       FIG. 5A  illustrates a retinal melatonin suppressor  100  in the form of eyewear having at least one lens  103 ,  104  and a photoluminescent material including nanocrystals (as shown, for example, in  FIG. 3 ) applied to substantially all of each lens  103 ,  104  to emit photons at a selected wavelength, λ B , in the direction of a retina of a wearer of the suppressor  100  in response to incoming or source light, λ A . Thus, the light provided to the wearer&#39;s retina comprises the emitted light, λ B , plus that portion of the incoming light, λ A , that is not blocked by the lens  103  or absorbed by the nanocrystals. Note that, although both lenses  103 ,  104  are illustrated as having the photoluminescent material applied essentially identically, this is not a requirement and the photoluminescent material may be applied differently to each lens  103 ,  104 . Each lens  103 ,  104  can be any optical device used to pass light on to, or focus light into, the eyes of a wearer including but not limited to a corrective lens, a sunglass lens, a monocular or binocular lens, etc. In the illustrated embodiment, the suppressor  100  includes a wearable frame  105 , with handles  101  connected by a pivot  102  with the frame  105  and at least one optical lens  103  supported by the wearable frame (also as  104 ). As best shown in  FIGS. 5B-5E , each of the at least one lens  103 ,  104  in the illustrated embodiment includes a substrate  107  that is substantially transparent to at least a portion of the visible light spectrum and a photoluminescent material  108 ,  109 ,  208  applied to the substrate  107  that emits electromagnetic energy of at least a selected wavelength, λ B , after being exposed to a source spectrum of electromagnetic energy, λ A . 
     Furthermore,  FIGS. 5B-5E  illustrate different techniques whereby the photoluminescent material may be applied to substrate  107 . In  FIG. 5B , the photoluminescent material  208  is more or less uniformly distributed throughout the substrate, which may be achieved through any suitable process for impregnating or dyeing the substrate material with the photoluminescent material. Alternatively, as shown in  FIGS. 5C and 5D , the photoluminescent material  108  can be applied as a layer to either or both of an external surface (i.e., facing incident light) or an internal surface (i.e., in the direction of the emitted light) of the substrate  107 , although an embodiment applied to only the internal surface is not shown. Further still, as illustrated in  FIG. 5E , the photoluminescent material  109  may be non-uniformly distributed within the transparent substrate  107 . For example, as shown in  FIG. 5E , one or more layers of the photoluminescent material  109  are coated on inner surfaces of the substrate  107  in a sandwich-like structure. The layers illustrated in  FIGS. 5C-5E  may be created using any suitable deposition technique, such as dielectric coating, spray or spin coating, sputtering, diffusion into the substrate, the use of a polymer sheet attached via electrostatic force, the use of a polymer sheet attached via a layer of adhesive, the use of multiple substrate layers each having internal layers that are subsequently laminated together, etc. 
     Although the suppressor  100  illustrated in  FIG. 5A  is illustrated in an eyewear embodiment (i.e., including a the frame  105 , etc.), it will be appreciated that the suppressor  100  may comprise a stand-alone optical device, such as a contact lens or unmounted lens. It is further noted that any of the optical devices described herein (including, for example, the lenses  103 ,  104  as shown in  FIGS. 5A ,  6 A, and  7 A) can be made of any material known to be used in the production of optical devices and to which the photoluminescent material  108 ,  109 ,  208  can be applied, including but not limited to glass, plastic, polycarbonate, polyurethane, and TRIVEX™ lens material. Regardless of the material used, various properties of the substrate material may be exploited according to various embodiments described herein. For example, if the substrate material is glass, and such type of glass has (or is otherwise treated or modified to have) ultraviolet (UV) blocking properties, the emitted light, λ B , would not include UV light (or at least substantially attenuated UV light) because this light must pass through the substrate  107 . Thus, the UV light that would otherwise be blocked by the substrate material can be used beneficially as the source of blue light if the layer of photoluminescent material with nanocrystals is placed on the external surface of the substrate as shown, for example, in  FIG. 5C  and is capable of transforming UV light into visible light that can be transmitted through the substrate material. 
     The human eye is equipped with a natural shutter called the pupil that controls the amount of light coming into the eye and, consequently, incident upon the retina. As intensity of incident light upon the retina increases, the pupillary reflex causes the pupil to constrict thus diminishing the incidence of all light, including beneficial light, incident upon the retina. In the context of the instant disclosure, this reflex could diminish the otherwise beneficial light emitted by the photoluminescent material. Thus, it may be desirable to provide the photoluminescent material on only a portion of an optical device such that the overall perceived irradiance is not increased to the point that the pupillary reflex negates or attenuates any beneficial effect. For example, by selecting certain portions of the lens  103  on which to include photoluminescent material, the effective incoming emitted light on the retina may be improved because the pupil does not constrict. 
     Furthermore, research has shown that melatonin distribution on the retina is not uniform and more therapeutic light may be most beneficial when applied to that portion of the retina with more photoreceptors. As known in the art, the visual field perceived by the brain is actually inverse to the structure of the retina. That is, for example, light entering from above the eye is actually projected onto the inferior portion of the retina, whereas light entering from the temporal side of the eye is actually projected onto the nasal portion of the retina. Thus, in one contemplated embodiment, a portion of the optical device with photoluminescent material is such that light emitted therefrom passes through the pupil to a nasal portion and/or inferior portion of the retina. In other embodiments, other techniques may be used to direct a portion of the emitted light from the optical device onto a specific portion of the retina through the pupil. For example, a portion of the lens  103  can be adapted at a different flat angle or concave angle to specifically direct incoming light. Examples of such embodiments are further illustrated with respect to  FIGS. 6A-6E  and  7 A- 7 E. In particular,  FIG. 6A  shows eyewear  100  where the photolumincscent material is applied only to a first portion of the lenses  103 ,  104 , e.g., to the upper half of the lenses  103 ,  104 . Alternatively,  FIG. 7A  shows eyewear  100  where the photoluminescent material is applied only to a second, smaller portion of the lenses  103 ,  104 , e.g., to the upper temporal quadrant of the lenses  103 ,  104 . Once again, it is noted that the lenses  103 ,  104  in the embodiments shown in  FIGS. 6A and 7A  do not necessarily need to be equivalent in terms of application of the photoluminescent material. 
       FIGS. 6B-6E  and  7 B- 7 E are taken along the cut line shown in  FIGS. 6A and 7A , respectively, and illustrate the lens  103  as mounted in the frame  105 . Note that the embodiments illustrated in  FIGS. 6B-6E  and  7 B- 7 E are essentially the same as those illustrated in  FIGS. 5B-5E , with the exception of the extent (i.e., the area or portion of the substrate) to which the photoluminescent material  108 ,  109 ,  208  is applied to the substrate  107 . As shown in  FIGS. 6B and 7B , the photoluminescent material with nanocrystals  208  is uniformly distributed throughout the substrate, whereas in  FIGS. 6C and 7C , the photoluminescent material with nanocrystals is placed as a coated outer layer  108  on an upper external surface of the transparent substrate  107 . In another embodiment (not shown), the layer is only placed as a internal layer on an upper internal surface of the transparent substrate  107 .  FIGS. 6D and 7D  illustrate two upper layers  108  with nanocrystals placed as both an external layer and an internal layer  108  on both the external and internal surfaces of the substrate  107 . As shown in  FIGS. 6E and 7E , one or more layers having photoluminescent material  109  are sandwiched within the transparent substrate  107 , as described previously. Once again, the deposition techniques described above may be employed when applying the photoluminescent material to the lenses  103 ,  104  as shown in any of the embodiments illustrated in  FIGS. 6B-6E  and  7 B- 7 E. 
     While various different configurations are shown as  FIGS. 5A-5E ,  6 A- 6 E and  7 A- 7 E, other possible configurations are contemplated. By way of a nonlimiting example, the use of clip-on lenses, the treatment by an incoming light exposing only part of the lens, and the use of additional light attenuating/blocking coatings in addition to the nanocrystal layer(s) are also contemplated. 
     In another embodiment, an optical treatment system is contemplated with a source such as a lamp, LED(s) or other light source (illustrated for its radiation as λ A ) to emit a source light having a desired spectrum. The system further includes an optical device such as the above-described lens  103  having a photoluminescent material applied to the lens  103  (for example, as described in any of the embodiments discussed above) to emit photons responsive to the source spectrum. In a preferred embodiment, the source spectrum includes invisible and near-visible UV light. 
     Finally, in yet another embodiment, the benefits described above may be provided with a separately-provided, potentially temporary coating for an optical device. For example, such coating may comprise a fixation matrix (such as a fluid, gel or other form having suitable viscosity to allow application of the coating to optical device, or being sufficiently flexible to be applied to a surface) and quantum dots of any desired concentration relatively uniformly suspended within the matrix. For example, in one embodiment, the fixation matrix may comprise a flexible polymer substrate that adheres to the optical device via electrostatic forces or a suitable adhesive. In another embodiment, the fixation matrix may include a transport fluid or gel for adhesion onto an optical device after stabilization on the optical device. For example, the fixation matrix may comprise a liquid form that, when sprayed on an optical device, dries to form a coating on the lens  103 . As with the previously described embodiments, incident light on the coating causes the emission of photons at a desired wavelength range, e.g., 420 to 485 nm in response to invisible or near-visible UV light. 
     It is understood that the preceding is merely a detailed description of some examples and embodiments of the present invention and that numerous changes to the disclosed embodiments can be made in accordance with the disclosure made herein without departing from the spirit or scope of the invention. For example, rather than strictly therapeutic implementations, the techniques and structures described above could be applied to a partially or purely cosmetic application. In such an application, the photoluminescent material could be applied in a manner to enhance the appearance of a wearer of, for example, eyewear configured as described above. The preceding description, therefore, is not meant to limit the scope of the invention but to provide sufficient disclosure to one of ordinary skill in the art to practice the invention without undue burden.