Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
1998-12-16
2003-04-01
Schwartz, Jordan M. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C623S006240, C606S005000
Reexamination Certificate
active
06540353
ABSTRACT:
TECHNICAL FIELD
This invention relates to a contact lens that restores the ability to focus on objects within a range of distances near to the user (referred to as “natural accommodation”), while retaining the ability to see distant objects. More specifically, this invention relates to a contact lens with a conventional spherical concave surface conforming to the curvature of the eye (base curve) and having a non-conventional convex surface (optic curve) combining spherical and non constant aspherical curvature resulting in an optical system that provides true monocular presbyopic correction (correction of presbyopia in each eye independently, instead of partial or full distance correction in one eye and partial or full near correction in the other) and restores the phenomenon of “natural accommodation.” Additionally, the invention affords a methodology of fitting that substantially reduces the skill and experience required by the contact lens fitter to a very basic level while affording a high degree of clinical success and patient satisfaction.
Normally between the ages of 40 and 45, presbyopia or old sightlessness is brought about by loss of elasticity of the crystalline lens of the eye, causing blurred vision at near points due to the reduction of the ability of the eye's natural lens to accommodate the changes in curvature necessary to focus on both near and distant objects.
When a person is free of presbyopia, the eye retains its full range of natural accommodation. This type of person's vision can be corrected by eyeglasses or contact lenses providing only the correction required for distance vision, and natural accommodation would automatically provide correction for near and intermediate distance vision.
BACKGROUND ART
For the contact lens wearer who requires presbyopic (or near vision) correction, in addition to distance correction, a variety of options have been available. These individuals may be fitted with single vision contact lenses corrected for distance, and wear reading glasses for near correction. Another alternative is to provide a contact lens for one eye that is corrected for distance vision and to provide a contact lens for the other eye that is corrected for near vision (this practice is referred to as monovision because only one eye is corrected for near vision), or the fitting of bifocal or multifocal contact lenses.
During the 1950's, a variety of contact lenses were designed for the correction of presbyopia. Theme contact lenses, although very innovative in design, met with only limited success because the only readily available material was Poly Methyl Methacrylate (Plexiglass), also known as PMMA which does not transmit oxygen. As bifocal and multifocal designs of the period were quite thick and heavy compared to conventional distance correction contact lenses, these presbyopic contact lenses were uncomfortable to wear for substantial periods of time. Additionally, the fitting of these bifocal and multifocal contact lenses required considerable time and skill on the part of the contact lens fitter.
During the 1970's, both soft contact lenses and rigid gas permeable (RGP) contact lenses were introduced with the availability of these new materials, renewed enthusiasm brought about several new designs for contact lenses for the correction of presbyopia.
RGP materials provide oxygen transmission through the lens material itself, and afforded new hope for the earlier designs developed in PMMA material. However, lens thickness and resultant patient discomfort continued to be a problem.
One of the early benefits recognized with soft contact lenses was the comfort and ease of fitting and, for this reason, by 1995 approximately 85% of new contact lens wearers are being fitted with soft contact lenses. As soft contact lenses command such a large share of the contact lens market, it is natural that considerable effort would be made to develop bifocal and multifocal contact lens designs in soft contact lens material.
There are two types of contact lens designs for the correction of presbyopia—Alternating (or Translating) and Simultaneous.
(1) In the alternating (or translating) vision technique, the lenses are very similar in design to bifocal eyeglass lenses in that the wearer sees through the distance segment in the upper portion of the lens when looking straight ahead and sees through a lower near vision segment when the eye (moves) to look down. Alternating vision lenses have proven to be successful in RGP designs, but have met with little success when designed in soft contact lenses.
Perhaps the reason that alternating vision soft contact lens designs were not as successful as the same design concept in RGP materials was because lens translation is necessary for this design to be successful. The translation from distance to near is achieved through the mechanical action of the lens resting on the lower eyelid and, when the eye looks down, the lens remains stable on the lower eyelid causing the pupil of the eye to translate from the distant vision portion of the lens to the near vision portion of the lens. Soft lens material by its nature caused this modality to fail as there was insufficient rigidity in the soft lens to remain properly positioned on the lower eyelid and often the lens would slip underneath the lower eyelid during translation.
(2) Simultaneous vision bifocal or multifocal contact lenses are either concentric or aspheric in design with focal power changing through different areas of the lens. Lenses are fitted so that distance, intermediate and near zones focus images simultaneously on the retina of the eye and the brain then separates out the image desired.
Theoretically, with adaptation, the ability to change focus naturally from near to far with no blurring in between can be achieved with simultaneous vision lenses in both RGP and soft contact lenses.
As alternating presbyopic designs proved to be unsuccessful in soft contact lens designs, most of the development work with soft contact lenses was done in the area of simultaneous presbyopic correction with concentric designs or aspheric designs.
During the 1980's, several designs of concentric and aspheric soft contact lenses were introduced. Soft aspheric multifocal contact lenses typically provided relatively weak reading addition power and therefore worked beat in early presbyopia.
Reading addition powers are referred to by eye care professionals as “add” power, and represent the difference between the distance correction and near correction prescribed by an eye care professional for eyeglasses or contact lenses. Accordingly, a prescription of “−3 with a +2 add” (which would be typical for moderate presbyopia) would mean that distance vision requires −3 diopters of correction, and near vision requires an additional 2 diopters of plus correction, resulting in −1 diopters of near vision correction. In conventional monovision, the dominant eye would be fitted with a −3 distance correction lens, and the other eye would be fitted with a −1 near correction lens.
This type of solution is often satisfactory in early presbyopia because the user still has some remaining visual accommodation and the needed add power is usually between +0.75 and +1.25, which is usually low enough for the brain to comfortably select the desired image in most people. However, conventional monovision becomes less satisfactory as, presbyopia becomes more advanced because the needed add power increases and visual accommodation has deteriorated further, so that the visual imbalance exceeds the brain's ability to select the desired image from the appropriate eye.
Typically, early presbyopes, would be between the age of 40 and 45, and would require add power of between +1.00 and +1.50 diopters. Moderate presbyopes would usually be between 45 and 55 years and would require add power of between +1.50 and +2.00 diopters. Mature presbyopes would usually be older than age 55 and require an add power of between +2.00 and &plus
Neuner George W.
Polyvue Technologies, Inc.
Schwartz Jordan M.
LandOfFree
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