Wraparound type frames have increased in popularity, especially as sports and fashion sunglasses. Conventional glasses protect the eyes from dust, ambient light, UV rays, direct light, and glare from the front only. Wraparound glasses have the advantage of multiple angle eye protection from these elements, and preventing UV rays from entering around the frame. Therefore, spectacle frames of the wraparound type (“wraparounds”) are especially useful in applications in the athletic fields for safety, general eye protection, and fashion.
Moreover, demand for wraparounds extends beyond athletic and safety fields. Incorporation of corrective lens elements into the wraparound lens allows for more general use of wraparounds in daily life; thus, enabling a wearer to smoothly transition from athletic scenarios requiring the multiple protections afforded by the wraparound design to mundane living scenarios, but also benefiting the wearer in athletic scenarios with enhanced vision thanks to prescription corrective lens elements.
It is known in prior art to manufacture non-corrective eyeglasses with wrap-around segments to shield the eye from elemental interference in the temporal visual field of the wearer.
It is also known in prior art to manufacture sunglasses or protective eyeglasses with spectacle lenses with refractive power.
Previous attempts to attach sunglass or sunshield elements to corrective eyeglasses or to wear sunglasses or sunshields over, in front of, or behind corrective eyeglasses are cosmetically unappealing, uncomfortable to the wearer, and impractical for use in casual, athletic, or safety-necessitated settings. Many conventional Prescription lenses have relatively flat base curves and thus limit the field of view due to physical size limitations and/or peripheral distortion.
It is accordingly an object of the present invention to overcome the difficulties and deficiencies related to prior art.
Under the present situation, the prescriptive corrective lens elements are embedded into the viewing region of either eye of a non-corrective lens for mounting in a wraparound frame to provide wider fields of view and greater eye protection yet offering corrective lens capabilities.
In early ophthalmic research, steeply curved prescription lenses were used at the detriment of eye protection and larger visual field. Tscherning's ellipse was found to be the relationship between curvature and through power, and identifies lens curvature and lens power combinations which minimize aberrations. Tscherning's ellipse assumes normal values for the index of refraction, lens thickness, and vertex distance parameters of a lens. Furthermore, Tscherning's ellipse retains values of ellipsoid shape and inclined orientation for certain lens parameters while the exact ellipse points may change.
The lower portion of the ellipse is the Ostwalt section, which describes flat front surfaces for ophthalmic prescription lenses. The upper part of the curve is the Wollaston section, which is a more steeply curved lens and has been unpopular historically. Such lenses were cosmetically unappealing and limiting in view.
Modern lenses have been manufactured with steeply curved spherical surfaces to serve various needs, such as natural lens replacement in the eye. Presently, most conventional prescription lenses are relatively flat, Ostwalt section, single vision miniscus lenses glazed into flat spectacle frames. Ostwalt sections are often treated with various processes to gain anti-reflective and/or reflective properties.
Corrective lenses are typically prescribed in various quarter-diopter strengths. Each power specification includes a spherical correction in diopters. Convergent powers condense light to correct for hyperopia, while divergent powers spread out light to correct for myopia.
For persons with astigmatism, two different correction powers in two different meridians are required which is described by the difference between cylinder and sphere power.
The axis component defines the location of sphere and cylinder powers, as the sphere is normally 90 degrees from the cylinder.
Hyperopia may be corrected with magnifying lenses. Presbyopia may be corrected with specific prism and base curve values.
Corrective lens elements can be produced in many different shapes, and the most common is ophthalmic or convex-concave. In the convex-concave lens, both front and back surfaces have a positive radius. This results in a positive convergent front surface and a negative divergent back surface. The corrective power of the convex-concave lens derives from the curvature difference between the front and rear surfaces.
The base curve, determined from the shape of the front surface of an ophthalmic lens, may be changed to suit optic and cosmetic characteristics across the entire lens surface.
Lenses are classified according to a refractive index; higher indexes conferring the advantage of thinner and lighter lenses, minimal edge thickness, and reduced internal reflections but at the cost of increased chromatic aberration, poorer light transmission, increased back and inner surface reflections, and degrading off-axis optical quality.
Optical quality of a lens is measured by dispersion, where lower dispersion measurement results in chromatic aberration. Dispersion is measured by an Abbe number (ABBE). In practice, ABBE's effect on chromatic aberration changes about 1:1, such that a small change in ABBE of about two units will not likely be noticed or beneficial but a change of about 17 unites may be beneficial for users with strong prescriptions that move their eyes and look away from the optical center of the lens. Since the human eye moves to keep the visual axis close to its achromatic axis, which is free of dispersion, and is insensitive to color in the periphery, the eye's ABBE number is independent of importance of the ABBE of the corrective lens. As the eye shifts its gaze, it moves to look through different parts of a corrective lens, which can be short distances away from the optical center. Thus, wearers who are sensitive to chromatic aberrations and have stronger corrective lens prescriptions and also look off the lens's optical center often should use lens material with the highest possible ABBE value at an acceptable thickness.
Power error is the change in lens optical power as the eye looks through different points on the lens area. It is least present at the optic center and worsens towards the lens edges. Power error is dependent on prescription strength and optimal spherical and aspherical form of the lens.
As the eye shifts from looking through the optical center of the corrective lens, the measured lens-induced astigmatism increases. Such increases impact visual peripheral clarity especially in spherical lenses with strong correction and legs-spherical base curve.
Distortion normally increases as corrective power increases. To combat lens induced power error, the best spherical form is selected for the lens.
Materials used in the manufacture of the corrective lens may consist of optical crown glass, plastic (CR-39), Trivex trivex, polycarbonate, and polyurethanes (high-index plastics), each possessing different values for refractive index, Abbe values, density, and UV cutoff.
The lens may be coated for antireflective, ultraviolet protective, and scratch resistant properties. Anti-reflective coatings make the eye behind the lens more visible, lessen back reflections of the white of the eyes, and bright objects behind the wearer, thus increasing the contrast of environmental surroundings as well as reducing light glare in night vision. UV coating may be used to reduce ultraviolet spectrum light wave transmission, thus decreasing retinal damage and the likelihood of cataracts during wear.
The above considerations are taken and applied to the present invention, thus creating a highly improved, cosmetically-appealing, and functional piece of eyewear for a multitude of activities and range of uses.