Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
  • G02C7/04—Contact lenses for the eyes

Definitions

• the apical radius of curvature and apical eccentricity of said novel surface are those of the coaxial osculating conicoid of revolution which osculates the novel surface at its apex, said apex being an umbilical point at which the derivative of curvature vanishes, the instantaneous eccentricity at any given point on said novel surface being quantitatively the same as that of the coaxial conicoid of revolution which osculates said novel surface at the given point and wherein the novel surface and the coaxial osculating conicoid of revolution have, at the given point, a common tangent plane, a common normal to said tangent plane, and identical principal curvatures and principal directions about said common normal.
• said novel surface When said novel surface is used as the posterior concave surface of a contact lens, its apical radius of curvature may lie within the range of from 6.0 to 9.2 mm, and its apical eccentricity may lie within the range of from 0.0 to 2.5, and along a meridian section of said novel surface, from its apex to its peripheral edge the change in instantaneous eccentricity resulting from the derivatives of eccentricity may lie within the range of from 0.00 to 2.00 eccentricity units.
• the apical radius of curvature of the front convex surface of the contact lens of this invention may lie within the range of from 4.5 mm to 15.0 mm and its apical eccentricity may lie within the range of from 0.0 to 2.5 and along a meridian section of said novel surface from its apex to its peripheral edge, the change in instantaneous eccentricity resulting from preselected derivatives of eccentricity may lie within the range of from 0.00 to 2.0 eccentricity units.
• the novel aspheric lens of this invention is designed to provide a concave posterior aspheric surface of revolution which is substantially of the shape of the front surface of a cornea to which the lens is applied, said back surface of the lens combined with the front surface of the lens provides correction for the refractive error of the eye and correction of presbyopia when it exists.
• the novel surface of the contact lens of this invention is the posterior surface of the lens of this invention
• the front convex surface may be spherical, toric, conicoid of revolution, general ellipsoid, or the novel surface.
• the general ellipsoid has a major, a mean, and a minor axis, each of which may be used as the axis of the front surface, which axis is generally coaxial with the axis of the novel surface, but may be tilted for the purpose of introducing prism into the lens.
• the novel surface of the contact lens of this invention is the anterior convex surface
• the posterior concave surface may be spherical, toric, conicoid of revolution, or general ellipsoid about its major axis, or the novel surface.
• the two surfaces may be coaxial or tilted with respect to each other to induce prism into the lens.
• This invention describes a corneal lens in which the concave posterior surface is toroidal, in which the concavity has a given radius in the horizontal meridian and a different radius, generally smaller, in the vertical meridian.
• the posterior concavity is provided with one or more discrete areas which extend out from the generally concave contour.
• the facets or protuberances constitute the only portion of the lens which actually contacts the cornea.
• eccentricity may be expressed in the form of a Taylor series. Using MacLaurin's formula, the eccentricity of modified ellipsoid can be written: where e x given by (3) is defined as the generalized or effective eccentricity.”
• Patent No. 3,227,507 Corneal Contact Lens Having
• the inner concave surface of the contact lenses of the Feinbloom patent has an optic zone area an inscribed sphere of radius r o .
• the spherical optic zone usually varies from 6 to 7.50 mm in diameter.
• the zone of inner surface beyond the central spherical optic zone may be an elliptical torus, or toric ellipsoid, or general ellipsoid, or some variation thereof, depending upon grinding and polishing procedures used.
• Aspheric Corneal Contact Lens Series defines the posterior corneal surfaces of the contact lenses of the lens series disclosed as conicoids of revolution including prolate ellipsoids, paraboloids and hyperboloids of two sheets, and shows the domain of the two parameters which define each lens in the series, apical radius of curvature and eccentricity.
• the aspheric surface of the contact lens of the invention is a conicoid of revolutionas determined by two parameters within a two dimensional domain; apical radii of curvature ranging from 6.50 to 8.50 mm and eccentricity ranging from 0.4 to 1.6, see Figure 1.
• the novel surface of the contact lens of this invention distinguishes from the prior art and in particular from the aforedescribed Volk invention of United States Patent No. 3,482,906 by defining the aspheric surface of the lens of the present invention by at least three predetermined parameters: apical radius of curvature; apical eccentricity; and derivatives of eccentricity, i.e. one or more of the first, second, third, etc.
• the apex of the novel surface may be considered a circle of latitude reduced to a point and can be numbered 0.
• the coaxial conicoid of revolution which osculates the novel surface at its apex can then be considered as part of the continuum of coaxial osculating conicoids of revolution whose osculations at the successive circles of latitude delineate the novel surface.
• n 1
• the parameters and associated dimensions of the coaxial osculating conicoid of revolution which osculates the novel surface at its apex are utilized as though they are of the preceding circle of latitude.
• ⁇ x n from the apex A n of the nth coaxial osculating conicoid of revolution to the plane of the nth circle of latitude of the novel surface.
• s n the distance from the plane of the nth circle of latitude to C n .
• d n the distance from A o to C n .
• Equation 16 Applying the actual values to Equation 16, r m(1) is calculated to be 7.5000001200 mm.
• h n f ap(n) - ⁇ x n . (22)
• h 1 is calculated to be 6.2499969167 mm.
• d 1 is calculated to be 7.5000000000 mm.
• the distance g n Of the focus F n of the coaxial osculating conicoid of revolution which osculates the novel surface at the nth circle of latitude, from the apex A o of the novel surface, is determined by the following equation:
• Equation 26 g 1 is calculated to be 6.2499979167 mm.
• FIGURE 5 is an exaggerated schematic representation of a meridian section of the novel surface of increasing eccentricity of the lens of this invention, and includes the meridian sections of three of the coaxial osculating conicoids of revolution which osculate the novel surface at three circles of latitude.
• XX' is the axis of revolution of the novel surface AAA, and of the coaxial osculating conicoids of revolution BBB, CCC, and DDD, which conicoids of revolution osculate the novel surface at circles of latitude 1-1, 2-2, and 3-3 respectively.
• FIGURE 6 drawn to scale, demonstrates the difference in contour between a meridian section of the novel aspheric surface of revolution of the contact lens of this invention of increasing eccentricity whose parameters and coordinates are presented in Table 1, and a meridian section of the coaxial osculating conicoid of revolution which osculates the novel aspheric surface of revolution at its apex, and whose parameters are identical to the r apex and e apex of the novel surface.
• Table 1 a meridian section of the coaxial osculating conicoid of revolution which osculates the novel aspheric surface of revolution at its apex, and whose parameters are identical to the r apex and e apex of the novel surface.
• XX' is the common axis of revolution of the novel surface whose meridian section is AAA and of the coaxial osculating conicoid of revolution which osculates the novel surface at its apex and whose meridian section is EAE.
• the posterior concave surface of the contact lens is the novel surface and the eccentricity decreases along a meridian section from the apex to the periphery.
• the first derivative of eccentricity will be utilized.
• FIGURE 7 is an exaggerated schematic representation of a meridian section of the novel surface of decreasing eccentricity of the lens of this invention, and includes the meridian sections of three of the coaxial osculating conicoids of revolution which osculate the novel surface at three circles of latitude.
• XX' is the axis of revolution of the novel surface AAA, and of the coaxial osculating conicoids of revolution BBB, CCC, and DDD, which conicoids of revolution osculate the novel surface at circles of latitude 1-1, 2-2, and 3-3 respectively.
• FIGURE 8 drawn to scale, demonstrates the difference in contour between a meridian section of the novel aspheric surface of revolution of the contact lens of this invention of decreasing eccentricity whose parameters and coordinates are presented in Table 2, and a meridian section of the coaxial osculating conicoid of revolution which osculates the novel aspheric surface of revolution at its apex, and whose parameters are identical to the r apex and e apex of the novel surface.
• XX' is the common axis of revolution of the novel surface whose meridian section is AAA and of the coaxial osculating conicoid of revolution which osculates the novel surface at its apex and whose meridian section is EAE.
• the posterior concave surface of the contact lens is the novel surface .
• dx 0.000001 mm.
• this third example is depicted graphically in FIGURE 9.
• the novel surface it is desirable for the novel surface to have a small rate of change in eccentricity in the vicinity of the apex of the surface and to have an accelerating increase in the rate of change in eccentricity with increasing distance from the apex.
• e is a small value within the range from 0.000 to 2.500, a value of 0.300 for example, it is desirable for e to increase with increasing x, and where e apex is a large value within the range, a value of 1.350 for example, it is desirable for e to decrease with increasing x.
• the usefulness of the novel surface as the posterior surface of the lens of this invention depends upon the fact that substantially. constant eccentricities may be achieved in the apical area of the novel surface while the peripheral area changes relatively rapidly in eccentricity to enable the novel surface to conform to the complimentary part of the cornea.
• the apical eccentricity should be a small value, generally less than 0.300, and should increase slowly to the edge of the central part of the novel surface which is an area of about 3.5 mm in diameter.
• the eccentricity changes more rapidly and the rate of change increases with increasing distance from the apex of the novel surface, so that the contour of the novel back surface of the lens of this invention approximately matches the contour of the cornea to which the lens is applied.
• the apical eccentricity should be a relatively high value, 1.000 or greater, and the eccentricity should change very little from its apical value to the edge of the central area, which is about 3.5 mm in diameter, and should then decrease in an accelerated manner to the periphery of the novel surface so that the contour of the novel surface of the lens of this invention approximately matches the contour of the cornea to which it is applied.
• the novel aspheric surface of revolution of the lens of this invention can be accurately produced by a numerically controlled lathe with a cutting tool having a fine steel or diamond cutting point, the cutting point passing through a series of points having the x and y coordinates calculated for the surface, as the lens rotates about its axis of revolution.
• the cutting tool point may move linearly from point to point on the surface or may move in small arcs from point to point, using circular interpolation to locate the center of curvature for each small arcuate movement of the cutting point of the tool. Since the point to point movements of the cutting tool point may be very small, linear motion of the cutting tool point is quite satisfactory.
• the apparatus consists of a measuring microscope having a lens mount which provides means for tilting the axis of the novel surface about an axis perpendicular to both the microscope optical axis and the optical axis of said novel surface as well as means for translational movement of the lens, to cause said normal to the novel surface to coincide with said microscope optical axis for measurement of the principal normal radii of curvature, r meridian , r m , and r transmeridian , r t , when said optical axis and said novel surface axis are inclined an angle ⁇ with respect to each other.
• the instantaneous eccentricity is then determined by means of the following equation:

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• Health & Medical Sciences (AREA)
• Ophthalmology & Optometry (AREA)
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• Optics & Photonics (AREA)
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• 1985
  • 1985-08-08 WO PCT/US1985/001494 patent/WO1987000936A1/fr not_active Application Discontinuation
  • 1985-08-08 AU AU47213/85A patent/AU594308B2/en not_active Ceased
  • 1985-08-08 JP JP50360185A patent/JPS63500403A/ja active Granted
  • 1985-08-08 EP EP19850904046 patent/EP0231174A4/fr not_active Withdrawn

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