This invention relates to ways to improve the capability of contact lenses with respect to user experience, after the lens package is opened, post-shipment and storage.
After manufacturing, a contact lens can interact with its packaging during storage or shipment. Efforts have been made by various entities to reduce these interactions. In general the minimization of lens-to-package interaction should be optimized. In some situations, it is suspected that there may be instances where the lens becomes folded (or at least slightly folded) during storage, even if unfolded when placed on the eye. Depending on the type of lens material, the effect of such folding could range from a handling inconvenience to an effect on the lens optical properties.
After reviewing this condition, the inventors have successfully created a “low head space” condition for the lens in the package, while retaining high manufacturing efficiency in areas related to yield, throughput and capital employed. In other words, it is felt that providing for minimal space (i.e., “low” “head space”) between the lens and the cover of the package would be beneficial to reduce the possibility of lens folding or inverting (that is, the lens flipping over..
The parameters involved in the project to provide “low head space” are:
Conservation of lens design—lens interaction with the packaging post-manufacturing should be minimized.
Customer experience—any negative customer experience should be avoided.
Sterility—the sterility barrier (namely the heat seal between the foil and package) should be considered, both on the manufacturing line and during shipment.
The following terms will be used:
As a result of our efforts, lens package arrangements with reduced head space were generated, using two different techniques:
As will be seen, lens folding during storage and handling post-manufacturing can be reduced using either method. This improvement takes a small amount of time (optimally, less that 30 minutes) to physically implement in manufacturing, costs a very low amount to provide for, and will have practically no effect on manufacturing.
The packages described by this invention all have reduced head space. From input of general parameters provided by users of these type packages, it was chosen to have packages containing dimples that will be geometrically equivalent (or even less intrusive) to the dimples described therein. So, specifically, packages were designed with sag equal to or less than 1.90-mm, or volume displaced equal to or less than 360 μl. Combined with the existing primary packaging, it has been found that such conditions provide for reduction in folded lens rate during shipping and handling. As well, lenses stored or having an extended time in low head space packages in a “foil down” orientation now have characteristics closer lenses stored in a “foil up orientation.”
A specific dimple die is provided herein, as seen in
The packages described by this invention all have reduced head space. The reduced head space is obtained by either a saline solution adjustment, a concave on the foil above the bowl of the primary package, or a combination thereof. It is important to understand that, in particular, managing the proportional size of folded lenses during shipping and handling is linked to the head space and shape of a particular package, regardless of the method used to achieve the low head space. The headspace expressed as a percentage of the total cavity volume desirable to achieve low folding is dependent upon the cavity shape itself. Thus, the examples included in the present specification are not intended to limit to the scope of this invention, but rather to serve as relevant examples.
From general observations provided by users of these type packages, it was chosen to have packages containing dimples that will be geometrically equivalent (or even less intrusive) to the dimples described therein. It was determined that sag would be the most relevant quantity to define the foil deflection for the dimples of a diameter much smaller than the bulb opening (namely the 13-mm diameter size family in the case of subsequent examples). Sag has been found to be a better metric than displacement for a small diameter, because the foil increases the displacement well beyond the calculated geometric displacement of the dimple itself. Calculated displacement, on the other hand, should be the most relevant quantity to define foil deflection for dimples of diameter close in size to the bulb diameter (namely the 20-mm family).
In a first set of experiments, contact lens manufacturing lines were used under experimental conditions to produce packages with varying amount of head space, comprised between 34% of the total volume (950 μl, or typical for lens packages) and 7% (1350 μl, or fill of full bowl). During these experiments, the influence of head space versus fold was assessed.
The graph of
In a second set of experiments, packages with low head space were created, using a dimple die in the foil above the lens bowl, one example of which is seen in
During the first phase of the design, a variety of dimple shapes were evaluated using an offline heat seal unit. The packages were fed in the machine and a heat seal die modified to accommodate a center piece pushing the foil inward as the die approximated the foil. As well, the inventors also reduced head space by a combination of difference dimples and dose volumes. From handling a quantity of approximately 30 lenses for each designs, it appeared that the lenses with any type of chamber dome Bathtubs, chamfered, wedge have been trialed (centered or not centered) had approximately 50% of the lenses stuck between the foil and the bowl (not free floating). It was decided that these options were not viable. As well, the packages made with tapered shape (“wedge”) exhibited a large amount of creasing at the foil, which affects seal quality and the sterility. These shapes were also discarded as options.
After this first screening it was determined that a smoothly transitioned shape was best suited for the application. Examples of such shapes may be, but are not limited to: spherical, parabolic or elliptical shaped dimples.
The graph of
In a third set of experiments, only continuous round dimple shapes were created. They were run on standard manufacturing equipment. The packages were focused on a combination of 13-mm and 20-mm dimples The 20 mm dimples have several types of patterns embossed to make sure the lens does not stick to the foil. The main take-away for this study was to focus on simple embossed patterns versus complex repetitive ones. Indeed, however, it was found that these patterns lift the lens edges away from the main foil surface, thereby eliminating the possibility of suction cupping onto the foil.
An added benefit for the user is that it becomes possible to make the patterns with aesthetically desirable shapes on the package:
1—By making the foil “matte” in the case of a small pattern.
These examples are meant to highlight the principle of the invention and are not limited to these specific patterns.
The packages with a pattern confirm the hypothesis that providing an irregular foil surface to the lens, even when the package is stored in a “foil down” position, avoids suction cupping that may alter slightly the effect of the lenses. The table of
In addition to reducing the lens-to-package interactions, as a result of these tests, some basic functional design considerations were derived for the dimpled packaging. These design considerations highlight further refinements of the dimple process, and are not intended to be limiting the general scope of the invention.
The high sag/high displacement dimples are designed to reduce the head space in the package enough to provide a bubble size reduction to the desired range without changing the current qualified dose volume in the 900 to 1000p1. In order to achieve this, the two dimple die designs used are described in
Evaluation of Dimple Combined with a Dose Volume Increase
Increasing the saline dose volume enough to remove any lens-to-package interaction has a drawback that under some opening techniques, some solution is pushed out of the package at opening. This is not optimal for customer experience. Deforming the foil enough to eliminate lens-package interactions at the same dose volumes also has a perceived drawback. The foil deformation is large enough to increase the risk of foil undulations occurring in the heat seal area. A solution using both techniques, each used to a lesser degree, was evaluated.
In a fourth set of experiments, dimples of lower sag and displacement were designed and paired with dose volumes slightly elevated. As already discussed,
The foregoing is to be understood to be subject to minor modifications, which will not depart from the spirit of the invention, which is to be understood from the attached claims and their equivalents.
This application is a Non-Provisional of U.S. Ser. No. 61/788,952, filed Mar. 15, 2013. The complete disclosure of the aforementioned related U.S. patent application(s) is hereby incorporated herein by reference for all purposes.
Number | Date | Country | |
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61788952 | Mar 2013 | US |
Number | Date | Country | |
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Parent | 14185207 | Feb 2014 | US |
Child | 15234354 | US |