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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to the assembling of spectacle lenses by
eyecare professionals which previously have been ground to order by
wholesale laboratories. This new system allows retailers to give "while
you wait" service and has particular utility when multi-focal segments,
progressive or blended additions, abrasion resistant coatings,
anti-reflection coatings, asphericity, photochromics or other tints,
polaroid filters, or other features are needed in addition to standard
single vision focussing power.
Eyecare professional retailers including opticians, optometrists and
ophthalmologists often carry an inventory of finished single vision
prescription lenses in-house. They are able to deliver about 30% of their
patient's orders from inventory by selecting the appropriate lens and
edging them into the selected frames chosen by individual patients.
The remainder of their orders are sent to wholesale grinding labs for
processing. Wholesale lab grinding is necessary because many prescriptions
require features beyond single vision focussing power that make
inventorying them impractical and too expensive. Because the number of
individual permutations is nearly infinite, wholesale grinding labs carry
an inventory of semi-finished blanks in a sufficient variety to cover most
orders. Each category of semi-finished blank covers a huge variety of
individual prescription possibilities.
The problems with this state of the art are varied. Individually ground
prescription lenses are subject to variations in power, thickness and
optical center location because of the complex process needed. The state
of the art does not allow all lenses to be finished with exact or often
tolerable specifications. This same complex process is expensive, cost
inefficient and creates delays in delivery usually from 3 days to 2 weeks.
In addition patient pressure for delivery often forces retailers to
dispense eyeglasses that are less than optimum with respect to their
specifications. This often causes eye strain, headaches, and partial loss
of visual function.
Typical prior art patents include U.S. Pat. Nos. 993,812; 1,267,014;
1,304,421; 1,948,636; 2,033,101; 2,330,663; 2,611,294; 3,248,460;
3,617,116; 3,628,854; 3,702,218; 3,771,858; 3,904,281; and 3,917,766.
It would, therefore, be highly desirable to provide the spectacle retailer
with lens covers which carry the particular bifocal, trifocal, special
vocational or aspheric correction required by that particular patient.
Prior art necessitated the use of a grinding laboratory because it would
be impossible to carry in stock all the possible combinations of
prescriptions, in addition to all the possible bifocal, trifocal, special
vocational or aspheric locations resulting from each patient's particular
facial and ocular measurements.
Attempts have been made to respond to this problem by providing composite
lenses as represented by the following patents: U.S. Pat. No. 4,547,049;
U.S. Pat. No. 4,576,623; U.S. Pat. No. 4,645,317; U.S. Pat. No. 3,877,798;
and Japan 552-10742. However, these have not been entirely successful for
a variety of reasons including the difficulty of forming the composites
use of expensive equipment, inconvenience, high cost and the limited
efficacy thereof.
Accordingly, it is a principal object of the present invention to provide
eyecare professionals with a new system which allows the simple,
convenient and expeditious assembly of spectacle lenses previously ground
to order.
It is a still further object of the present invention to provide a
combination eyeglass lenses as aforesaid which will allow eyeglass
retailers to readily provide "while you wait" service for a wide variety
of prescriptions, including multi-focal segments, progressive or blended
additions, abrasion resistant coatings, anti-reflection coatings,
asphericity, photochromics or other tints, polaroid filters, or other
features needed in addition to standard, single vision focussing power.
A further object of the present invention is to provide the eyeglass
retailer with very inexpensive lens over-lays which can be combined with
his own in-house stock single vision lenses to create a simply prepared,
large inventory of spectacle lenses at a reasonable cost.
A further object of this invention is to provide the patient with prompt
delivery and fitting of their prescription eyeglasses even when complex
additions are involved, and at a substantially reduced cost because all
the fabrication can be done on the premises of the eyeglass retailer.
Further objects and advantages of the present invention will appear
hereinbelow.
SUMMARY OF THE INVENTION
Accordingly, in view of the present invention it has now been found that
the foregoing objects and advantages of the present invention may be
readily obtained.
The eyeglass lens of the present invention comprises in combination a first
inner single vision prescription lens component with a selected diopter
correction and having a curved anterior surface and a curved posterior
surface, a second outer lens component having a range of diopter values
from -0.25 to -2.0 and from +0.50 to +2.0 diopters and having a curved
anterior surface and a curved posterior surface, preferably with the
curved anterior surface of the first lens being +0.07 to +0.12 diopters
steeper than the curved posterior surface of the second lens, a minus
ophthalmic adhesive optically and physically bonding together the anterior
surface of the first lens with the posterior surface of the second lens,
whereby upon pre-selecting the first and the second lens components, the
two can be optically and physically joined from a modular supply of both
types of lenses. The thickness of the edge and center of the second lens
component differ by a factor of at least 1.5 and preferably at least two,
which lends stability to the second outer lens component. It is preferred
that the second lens component have a diopter value of about -0.50. The
second lens component can include a bifocal or multi-focal addition in a
portion of its area as well as many other types of desired additive
features.
The foregoing construction readily and conveniently achieves the foregoing
objectives. It is simple and inexpensive to construct by a retailer on an
"as you wait" basis. The minus lens adhesive configuration is especially
advantageous as it allows the adhesive to flow evenly out to the edges
without assistance. This creates an optically inert lamination which
avoids problems with the optics of a laminated sandwich.
The construction of the present invention avoids the problems encountered
with a plano cover lens. The cover lens of the present invention is easy
to handle and does not create wavy surfaces. The flexibility of a thin,
plano cover lens often creates wavy and distorted optics. Thus, for
example, a -0.50 D. cover lens, having a diameter of 75 mm has an edge
thickness of 1.7 mm as compared to 1.0 mm in the center. This gives the
lens the needed stability and also makes it easier for semi-skilled or
even non-skilled retailers to accurately handle during lamination.
Further advantages of the present invention will appear herein.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more readily apparent from a consideration of
the following description and accompanying drawings which represent
illustrative embodiments wherein:
FIG. 1 is a cross-sectional view of a exemplificative eyeglass lens
combination of the present invention; and FIGS. 2 and 3 are alternate
embodiments of eyeglass lens combinations in accordance with the present
invention.
DETAILED DESCRIPTION
The present invention involves the lamination of a cover lens having a
defined diopter value range, and preferably a -0.50 diopter cover lens, as
the vehicle to deliver the extra features beyond single vision focusing
power to the final prescription. The cover lens is laminated to the
anterior surface of the single vision lens using a quick curing
ultra-violet adhesive which can be readily done by the retailer or a
wholesale lab. The -0.50 cover lens can, for example, be used to deliver:
1. Bifocals having any shape or style.
2. Trifocals having any shape or style.
3. Vocational segments having any shape or style.
4. Abrasion resistant coatings.
5. Anti-reflection coatings.
6. Polaroid filters.
7. Photochromic and other tints.
8. Asphericity for high powered prescriptions.
9. Progressive and blended additions.
The ultra-violet adhesives are preferred. These have a similar index of
refraction as the lens material so that it becomes optically inert with
respect to the finished laminate lens. Known materials can be readily
utilized for this purpose and include those adhesives which will both
suitably transmit light and provide the desired adhesive properties to
maintain the lenses in a laminated condition. Typical materials include
one or two-part curing adhesives, based on epoxy, acrylic, polyurethane or
silicone resins.
The present invention will be more readily understandable from a
consideration of the following illustrative examples.
EXAMPLE 1
Rx=+1.00+0.50.times.90
Add +2.00 Flat top Bifocal
Step #1. Transpose the distance prescription to minus cylinder form, i.e.
+1.50-50.times.180
Step #2. Add +0.50 D. to the spherical power of the Rx to compensate for
the effect of the -0.50 D. cover lens, i.e. +2.00-0.50.times.180
Step #3. Select a +2.00-0.50 single vision lens from stock. Clean the lens
using a low lint paper wipe and wipe with water. The purpose is to
thoroughly remove major dirt marks from the lens and wet the two surfaces.
Then spray another low lint paper wipe with acetone and go over the entire
lens to remove any grease and to dry the surfaces by the action of the
acetone which absorbs the water.
Step #4. Position the single vision lens in the lensometer and spot with
respect to axis and optical center location.
Step #5. Super-impose three dots on the posterior surface of the lens using
the three lensometer-made dots as a reference. Re-clean the anterior
surface using first water and then acetone.
Step #6. Select a +2.00 add -0.50 D. cover lens which is designated for a
distance single vision lens of +1.50 D. This assures that the two lens
components will have compatible mated lamination curves. Clean the -0.50
D. cover lens using the same technique as in Step #3.
Step #7. Position the -0.50 D. cover lens atop a flat low lint wipe on a
work area with the concave or posterior surface up. Drop 10 drops of
adhesive in the center of the lens forming a pool. Inspect the pool to see
that there are no bubbles or unwanted dirt or other foreign object. Bubbles
can be burst with a pin and can be avoided by holding the nozzle of the
adhesive container 2 mm. above the lens surface while forming the pool.
Step #8. Gently place the convex or anterior surface of the single vision
lens atop the adhesive pool with the three layout dots super-imposed over
the 180.degree. meridian of the -0.50 D. cover lens. The adhesive will
take a minute or two to spread out to the edges of the lens. This will
happen automatically and without help because of the described curve
compatability between the two lenses.
Step #9. After the adhesive has reached the lens edges everywhere, the
lenses can be re-aligned. No sticking takes place until the sandwich is
placed under ultra-violet light. Once properly aligned the sandwich can be
lifted for inspection. If there is no dirt or bubbles, it is placed under
ultra-violet light for curing. The cycle times are described earlier. If
the sandwich is not clean, the two lenses can be separated by sliding one
across the face of the other. They can then be re-assembled using the same
steps listed above.
Step #10. After full cure, the finished lens assembly is identical to any
standard surfaced lens with respect to edging, tinting, drilling, grooving
and frame assembly.
The foregoing lens is shown in FIG. 1. R.sub.1 is the raised portion of the
anterior surface of the cover lens. It represents a flat top bifocal having
a diopter value of +2.00 D. with an anterior curvature of +10.34 D. R.sub.1
=51.257 mm. R.sub.2 is the anterior surface of the cover lens having a
diopter value of +8.22 D. R.sub.2 =64.476 mm. R.sub.3 is the posterior
surface of the cover lens having a diopter value of -8.75 D. R.sub.3
=60.57 mm. The combination of R.sub.2 and R.sub.3 gives the cover lens a
power of -0.50 D. Assuming a center thickness of 1.0 mm. the edge
thickness at 75 mm will be approximately 1.7 mm when made from CR-39
plastic. Changes in thickness will occur with variations in center
thickness lens material and diameter, but the ratio of 1.5 to 2 times more
edge thickness than center thickness gives the thin veneer cover the needed
stability. R.sub.4 is the anterior surface of the single vision
prescription lens having a diopter value of +8.82 D. R.sub.4 =60.09 mm.
The significance of R.sub.4 is that it is a 0.7 D. steeper than R.sub.3
creating a minus lens configuration in the adhesive layer allowing the
adhesive to flow uniformly out to the edge from a centrally dropped pool.
This is essential to produce an inert optical contribution during the
lamination process. The optical power of the cover lens combined with the
optical power of the base lens equals the optical power of the combined
sandwich only when the adhesive layer has a slight minus configuration.
The posterior portion of the single vision lens has a toric surface with
the correction for astigmatism when needed. Naturally, the present
invention can readily be used when only corrections for far-sightedness or
near-sightedness are required.
EXAMPLE 2
Rx=-3.00+1.75.times.70
Add +2.50 Progressive Bifocal
Step #1. Transpose the distance prescription to minus cylinder form, i.e.
-1.25-1.75.times.160
Step #2. Add +0.50 D. to the spherical power of the Rx to compensate for
the effect of the -0.50 D. cover lens, i.e. -0.75-1.75.times.160
Step #3. Select a -0.75-1.75 single vision lens from stock and repeat the
steps in Example 1.
In the present example, a progressive powered reading area is furnished on
the anterior surface of a separate stock of -0.50 D. cover lenses. In a
like manner, all the different multi-focal segment shapes and combinations
will be available on the front of -0.50 D. cover lenses.
The foregoing lens is shown in FIG. 2. R.sub.5 is the anterior curvature of
the bifocal segment on the front of the cover lens having a variety of
diopter curvature values in accordance with the state of the art standard
procedures for manufacturing a progressive bifocal addition. The radius
becomes shorter as the progressive area increases in power toward the
bottom of the lens. R.sub.6 is the anterior surface of the cover lens
having a diopter value of +5.72 D. R.sub.6 =92.65 mm R.sub.7 is the
posterior surface of the cover lens having a diopter value of -6.25 D.
R.sub.7 =84.8 mm. This gives the cover lens a power of -0.50 D. and a
bifocal add of +2.50 D. R.sub.8 is the anterior surface of the
prescriptive single vision lens having a diopter value of +6.32 D. R.sub.8
=83.86 mm.
EXAMPLE 3.
Rx=+0.75-1.00.times.80
Single vision lenses with abrasion resistant and/or anti-reflection
coating.
Step #1. The Rx is already in minus cylinder form. No further transposition
is needed.
Step #2. Add +0.50 D. to the spherical power of the prescription to
compensate for the effect of the -0.50 D. cover lens, i.e.
+1.25-1.00.times.80
Step #3. Select a +1.25-1.00 single vision lens from stock and repeat the
steps in Example 1. The -0.50 D. cover lens in this case would also be a
single vision lens, but would have either an abrasion resistant as
anti-reflection coating on the anterior surface.
The foregoing lens is shown in FIG. 3. R.sub.9 is the anterior surface of
the cover lens having a diopter value of +5.72 D. This is the surface
having an abrasion resistance or anti-reflection coating. R.sub.9 = 92.657
mm. R.sub.10 is the posterior surface of the cover lens, having a diopter
value of -6.25 D. R.sub.10 =84.8 mm. This gives the cover lens a total
power of -0.50 D. R.sub.11 is the anterior surface of the single vision
prescriptive lens having a diopter value of +6.32 D. R.sub.11 =83.86 mm.
R.sub.12 is the posterior surface of the prescriptive lens having a
diopter value of -4.99/ -6.05 D. R.sub.12 combined radii are:
106.21/87.603 mm. for the toric surface.
A significant feature of the combination of the present invention is that
the curved anterior surface of the first lens is steeper than the curved
posterior surface of the cover lens, preferably from 0.07 to 0.12 D.
steeper. This creates a minus adhesive layer between the two lenses which
would allow the adhesives to flow easily out to the lenses edges. In
addition, this gives the layer of adhesive a slightly thicker lens at the
edge than the center thickness encouraging the liquid adhesive to run
evenly out the edge of the lens from a centrally dropped pool without help
of any kind from the technician. This simplifies prescriptions of the
eyeglass lens of the combination of the present invention and avoids wavy
optics.
In accordance with the present invention it is contemplated that the cover
lenses will be manufactured, packaged and shipped, unpacked, cleaned by
the laminating technician, marked for assembly, assembled together with
the single vision lens, and often stored under a wide variety of changing
temperature and humidity conditions.
It has been found that a plano powered cover lens is not reliable. For
example, when the posterior and anterior curves are nearly parallel as
must be in all plano powered lenses, and the center thickness is close to
1 mm, wavy optics result from warpage caused by humidity, temperature and
handling. Also, application of the adhesives and the adhesive layer itself
presents more of a problem. The adhesive will not spread evenly.
It has been found in accordance with the present invention that the powered
cover lens, and especially when the covered lens has a distance power of
about -0.50 D., these problems are eliminated. This gives the edge of the
cover lens about 1.5 to two times the thickness of the center in a 75 mm
diameter lens making the cover practical to pick-up, position and manage
throughout the process of handling and lamination. In addition, the plus
powered employments of the present invention are also advantageous to work
with and avoid problems of plano powered cover lenses. Further, the cover
lens of the present invention includes less unwanted magnification which
manifests itself as distortion to the wearer. This is especially important
with positive powered lenses.
Thus, the eyeglass lens combination of the present invention creates a
modular inventory of lens components which can be assembled using a simple
laminating technique and which can provide patients with a "while you wait"
service when desired. The eyeglass lens combination of the present
invention avoids the power, thickness, and optical center location errors
and variations commonly encountered in lenses surfaced by grinding labs.
In addition, the present invention provides consistent quality by using
factory-cast components and provides prescription eyeglasses of all types
with abrasion resistant coatings having the consistency of quality only
available from factory cast lenses. Anti-reflection coatings may be
applied conveniently and easily without lengthy delays and breakage
created by sending them to special coating houses. A wide variety of
features may be readily obtained, including polarized lenses, asphericity,
bi-focals, progressives, tri-focals and the like on a "while you wait"
basis. Further the present invention enables a wide variety of
prescriptions to be obtained on a cost effective basis without time
consuming extra procedures.
It is to be understood that the invention is not limited to the
illustrations described and shown herein, which are deemed to be merely
illustrative of the best modes of carrying out the invention, and which
are susceptible of modification of form, size, arrangement of parts and
details of operation. The invention rather is intended to encompass all
such modifications which are within its spirit and scope as defined by the
claims.
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