The evolution of a new ophthalmic lens has a development cycle: design, manufacturing, optical evaluation, visual performance. At some point in this cycle a decision must be made to 'go to market.' Often this involves the manufacturing and optical evaluation (quality assurance) more than the design and visual performance aspects, although these latter contribute to the explanation of benefits which can be crucial to a technically innovative design. In this paper the manufacturing aspects of any specific designs will not be considered. However, the inter-relationship between the remaining three items are so strong that it is not possible to treat each one in isolation. In order to cover these relationships this paper will progress through 2.5 cycles starting with the design aspects.
A patented new injection-molding technology, which already has been commercially licensed nonexclusively to leading Rx polycarbonate lensmakers and is now under development with leading contact lensmakers, gives very high moldpacking pressures (needed for maximum microsurface replication) without high birefringence (minimized by reducing constrictiveness during fill), even with high viscosity optical thermoplastic polymers.
Cast molding of contact lenses from a polymerizable monomer composition, encapsulated between two molds, offers a route to a highly reproducible product. Unfortunately, some of the reproducible characteristics are not desirable. In particular, the edge profile is often uneven and causes patient discomfort, or worse. To ensure a good quality edge with current molding processes, it is necessary to polish it. In the polishing steps the final edge profile can vary, but in addition other faults such as scratches and tears, not to mention general handling faults, depress yields and reduce the quality of a perfectly molded lens. This paper describes a process which not only produces a uniform, safe, and comfortable edge but which, by SPC methods, reduces all handling to a minimum and ensures the patient receives a healthy lens of consistently high quality.
This paper describes spectacle lenses which give the wearer greater ability to sense colors at the ends of the visible spectrum (red and blue). Natural visual sensitivity to these colors is substantially less than for those at the mid-spectral range. Because of the mechanism by which human perception of color takes place, design procedures are contrary to those which would be indicated by an instinctive analysis.
Today's corrected curve lenses are being challenged by newer aspheric lens designs. These lenses use flattened aspheric front surfaces to provide lenses that look better and more comfortable. Sola Optical's ASL trademark aspheric lenses in Spectralite trademark and Polycarbonate, have taken this a step further by combining the benefits of high index/low weight materials with the optical performance of Sola's aspheric lens design. This combination provides thinner, lighter, and better looking lenses while maintaining excellent visual performance. Sola engineers have identified the factors critical to understanding and managing the blurring effects of off-center aberrations in lenses. ASL lenses are up to 25% thinner, 30% lighter, and 30% flatter than standard plastic lenses without sacrificing optical performance. In addition, they reduce magnification so images appear more natural in size, as do the wearers' eyes.
The measurement of oblique astigmatism error and its oblique power of ophthalmic lens under identical conditions of the human visual system--such as the distance from the center rotation of the eye to the back vertex surface of the lens--viewing distance, and lens aperture using a Mach Zehnder interferometer is describe.
The resolution of diffractive, bifocal intraocular lenses was studied with regard to pupil displacement and diameter size through computer simulations, bench measurements and patient vision acuity measurements. Good agreement was obtained between these three methods of investigation. In particular we find that pupil displacements of the order of 1 mm reduce the resolution considerably for these lenses.
This paper describes a revolutionary new design for our intraocular lens which possesses two primary focal points and an increased depth of field, thereby providing the implant patient with both distance and near vision. The design incorporates both refractive and diffractive functionalities, with the latter being responsible for providing enhanced near vision for the implanted patient.
During the past fifteen years, Intraocular lens (IOL) haptic preferences have shifted from a variety of multi-piece haptic materials to single-piece PMMA. This is due in part to the research of David Apple, M.D., and other who have suggested that All-PMMA implants result in reduced cell flare and better centration. Consequently, single-piece IOLs now represent 45% of all IOL implants. However, many surgeons regard single-piece IOL designs as nonflexible and more difficult to implant than multipiece IOLs. These handling characteristics have slowed the shift from multi-piece to single-piece IOLs. As a result of these handling characteristics, single-piece lenses experience relatively high breakage rates because of handling before insertion and during insertion. To improve these characteristics, manufacturers have refined single-piece IOL haptic designs by pushing the limits of PMMA's physical properties. Furthermore, IOL manufacturers have begun to alter the material itself to change its physical properties. In particular, two new PMMA materials have emerged in the marketplace: Flexeon trademark, a crosslinked polymer and CM trademark, a material with molecularly realigned PMMA. This paper examines three specific measurements of a haptic's strength and flexibility: tensile strength, plastic memory and material plasticity/elasticity. The paper compares with Flexeon trademark and CM trademark lenses to noncrosslinked one-piece lenses and standard polypropylene multi-piece lenses.
Reactive low voltage ion plating (RLVIP) produces dense and hard coatings even on unheated substrates. These qualities are highly desirable for coating of plastic lenses. However, the thermal expansion coefficient of these dense coatings is much lower than that of plastic substrates. Hence, even a moderate temperature rise during deposition puts the coatings under extreme compressive stress because of the subsequent shrinking of the substrate during cool down. We report our experience and encouraging results with this coating process for the antireflection coating of ophthalmic lenses.
Current estimates of the percentage of anti-reflection coated lenses verses uncoated in the market today range
from 3% in the United States (US.), to 60% in Europe, to 80% in Japan. Currently upwards of 80% of all
prescription eyewear lenses dispensed are resin. Glass lenses lose market share yearly, as scratch resistant
coatings on resin lenses are improved. Photochromic resin materials are also improving and will shortly equal
the performance of glass photockromics. Until recently, the performance characteristics of ophthalmic lenses
were divided into two schools. In Europe, the emphasis was on keeping the reflections to an absolute minimum,
while in the Asian market the emphasis was on producing a lens, which had exceptional scratch resistance. A
typical European lens may average .4% reflection across the visible spectrum (400 to 700 urn.), while the Asian
lenses averaged in the 1.5% range. The growth ofAR coating in the U.S. 80 million pair a year total ophthalmic
market has been lagging foreign markets for several reasons.
An estimated 10 million pairs of photochromic prescription lenses were dispensed in the United States in 1989, essentially all based on a silver halide system suspended in an inorganic glass. A significant trend within the ophthalmic industry has been the growth of light-weight plastic lenses. In the United States market, the percentage of prescription eyewear made of plastic is now greater than 70%. With this increasing market penetration of plastic lenses, the desire for an acceptable plastic photochromic lens has also increased. As with any commercial product, in order to achieve consumer acceptance there exist several technical requirements for a plastic photochromic lens. These include the light transmission and color of the lens in both the unactivated and activated states, the speeds of darkening and fading, and the fatigue resistance or lifetime of the photochromic system. These requirements will be defined along with approaches to achieving them. The properties of the commercially available plastic photochromic lenses will be compared with the defined requirements.
In this paper the design and manufacture of ophthalmic multilayer broadband antireflection coatings with same residual reflective colors on the substrates for different refractive indices have been investigated. Somebody need to dispense spectacles which the two lenses are different optical materials with different refractive indices(e.g. nl.75,nl.52), and the residual reflective colors of the two lenses must remain the same. We designed tripl- layer antireflection coatings on the substrates which have different refractive indices. The residual reflective colors of these coatings have the same color position in the CIE color chart and have almost the same average reflective brightness. Also, we have found that the quartz crystal thickness monitor is the good method for preparing the AR coatings.
The most rapidly growing segment of the ophthalmic lens market is the 'thin and light' segment. A major force for this growth has been the consumer, who wants thinner, lighter and better looking eyewear. In fact, the consumer demand for thin and light lenses increased by over 44% last year. There are essentially three options that allow thinner, lighter and flatter (more cosmetically appealing) lenses. These include: (1) a higher index material (higher than standard CR-39 registered or glass), (2) an aspheric design, or (3) a combination of both. However, current high index materials have certain properties that can affect the optical performance and ease of processing of spectacle lenses. Also, most current aspheric designs benefit only hyperopes, which represent about 30% of the spectacle lens wearers. Sola's ASL aspheric single vision lens in Spectralite combines a patented new high-index material with a specially flattened and aspheric design. This unique combination optimizes the traditional thin, light, and cosmetic benefits of high index while achieving optical performance comparable to CR-39. And, unlike other aspheric lenses, ASL in Spectralite is available in both plus and minus prescriptions, allowing you to meet the needs of more patients than ever before.
Antireflection coated ophthalmic lenses, both glass and plastics, are very popular in Europe and Asia, while in the U.S. the ophthalmic lens manufacturers are just beginning to discover this add-on value. The reasons for the wide acceptance of, particularly, highly efficient broad band antireflection coatings in Europe and Asia are investigated, together with the reasons for their slow acceptance in the United States. Other types of coatings for ophthalmic lenses, for sun protection and laser protection, are also introduced. The discussion leads to deposition processes useful for coatings on plastic lenses. A brief evaluation of coating of prescription lenses vs. stock lenses, and of quality criteria for both types concludes this review paper.