Traditionally, the answer to good optical performance in single-vision lens design has been the use of steep base curves. This, unfortunately, results in a cosmetically poor lens as it is bulky and heavy. These steep base curves place the back of the lens at a considerable distance from the eye, making the eyes appear large (the "gold-fish bowl effect").

At Polycore, we realise that today's enlightened consumer demands more than just good vision - he requires an aesthetically pleasing product as well. We proudly present Polycore's Asphera 3. It is an aspheric lens that provides the wearer with greatly improved performance over the traditional spherical lens.

While maintaining identical visual acuity to the sphetrical lens, cosmetic appearance is greatly improved. In addition the Asphera 3 is light and thin, without the bulk of the traditional lens.

At Polycore, this technical achievement is accomplished with a front curve that is no longer of spherical shape.

The following graphs illustrate the way in which Asphera 3 helps overcome the early optical design barrier of a few years ago. We used a +6.00 Diopter prescription for comparison.

A good lens corrects a person's vision in every direction. For example, in Graph 1, the astigmatism for different directions of vision is kept below 0.2 Diopter spherical lens. Good vision is maintained for all directions up to 35 degrees.

The other factor. Mean Oblique Error or MOE shows us how the prescription power varies over the lens. An MOE of zero over the lens means that the prescription power dies not change over the lens. This idea is approximately achieved in a traditional lens as shown in Graph No. 1.

To achieve this performance, the traditional lens uses deep base curse. Consequently, the lenses are bulky with a plate height of 14.4 mm and a centre thickness of 8.6 mm for a 70 mm diameter lens as shown in Figure No. 1 above.

In designing the Asphera 3, we used a mush shallower base curve. We then compensated for the resultant higher OA and MOE from the center to the edge of the lens by adjusting the shape of the lens surface. The shape of the front curve is no longer spherical, hence the term aspheric.

It is easy to see the improvement in the bulkiness of the lens with nearly identical values of OA and Moe.

For the wearer, the immediate benefit of using the Asphera 3 is the reduction in magnification of his or her eyes. With the Asphera 3, the back of his or her eyes. With the Asphera 3, the back of the lens is placed closer to the wearer's eye. As a result, the magnification is reduced by as much as 30%, allowing the eye to appear more normal in size.

In addition, the Asphera 3 eliminates the distortion of images that are produced in viewing through a traditional spherical lens. to best illustrate this, hold an Asphera 3 and a traditional spherical lens and view a grid pattern at arms length ( see Figure No. 3 )

A unique feature of the Asphera 3 is that the design takes into consideration the physiological properties of the eye in "dynamic seeing". A simulation of exact geometrical movements of the eye was incorporated in the development of Asphera 3 which ensures that the wearer can adapt to the lens immediately.

For more information, write to us or phone anytime.