Seiko Free-Form Lens

Seiko Free-Form Lens Technology & Specifications


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Patented 100% back surface design technology

  • The patient’s entire prescription is three-dimensionally fused onto the back surface of the lens. This eliminates front-curve distortion, provid­ing total control of marginal astigmatism and power error
  • True, customized, Rx-specific aspheric power compensation in the progressive channel results in billions of optically precise prescriptions
  • All visual fields are significantly expanded, with consistently wide near vision


Seiko Succeed Ws and Succeed In­ternal Free-Form progressive addition lenses are made using a patented, technologically advanced design that 3-dimensionally fuses the patient’s entire prescription onto the back surface of the lens. This offers tremendous advantages over conventional front-surface progressive designs.

To begin with, the front surface shape magnification differences between visual areas are eliminated. In conventional progressive lenses, distortion is induced by the shape changes on the pre-molded front curve, and by power changes on the back. The front surface on Seiko Internal Free-Form lenses is a perfect sphere, eliminating distortion due to front surface shape changes (Fig 1).

The wearer experiences a consider­able reduction in overall size and skew distortion, with a virtual elimi­nation of image sway & swim (Fig 2).

A second advantage of internal free­form design is that, by placing the progressive surface on the back of the lens, it is closer to the eye. This considerably expands all the fields of view (distance, intermediate and near). These larger fields of vision in turn provide better image stability, greatly exceeding the limitations of conventional progressives (Fig 3).

Seiko Free-Form Lens

In conventional PAL design, any particular base curve covers a wide range of power. Consequently, each base curve is optimized only for a specific spherical Rx at the center of its range. Therefore, good visual acuity is only effective somewhere in the middle of the entire range for each base curve. This affects the reading area the most, due to the fact that it is “off-center,” meaning that power error and unwanted astigmatism are induced and automatically present. Therefore, optics are compromised by these naturally occurring primary aberrations in all prescriptions that fall outside this narrow band.

Seiko Internal Free-Form lenses fuse toric and progressive surfaces into one complex curve. Aspheric compensation is customized in the progressive channel based on the
patient’s complete Rx. This compen­sation specifically takes into consid­eration each sphere, cylinder, axis, prism and add power combination. This means that Seiko Internal Free-Form lenses can be surfaced into billions of unique Rx combinations (considering each sphere, cylinder, axis, prism and add), all of them ex­act. A conventional progressive lens can have, strictly speaking, only one optically precise Rx per base curve and add combination (generally around 65 total).

Seiko Internal Free-Form lenses pro­vide total control of off-center astig­matism and power error. This gives the lens accurate power throughout the expanded reading area. The design also incorporates aspheric power control in the corridor, along the entire principle meridian. This compensates for changes in vertex distance as well as the degree of vi­sual axis (rotation) as the eye focuses from distance to near. The resulting gradient cylinder control within the corridor vastly improves intermedi­ate vision.

Seiko Free-Form Technology


Quick Facts
Seiko Internal Free-Form lenses are new, innovative progressive lens products that feature Seiko Epson’s patented 100% back surface design technology. They have been avail­able world wide for over a decade, and are now available–with the latest design advancements–in the U.S. marketplace.

Seiko Internal Free-Form lenses are designed for people who appreci­ate wide distance vision and who require the widest reading and in­termediate areas. They are the per­fect first pair of progressive lenses, and ideal for replacement, or for patients sensitive to the distortion in regular progressive lenses.

These lenses owe their success to the exclusive design, which 3-dimensionally fuses the pa­tient’s entire prescription onto the back surface of the lens. This complex surface gives accurate
power throughout the reading area, provides gradient cylinder con‑
trol along the entire intermediate area, and has a significantly wider, distortion-free distance vision area.

Technically, the lens provides for total control of marginal astigma­tism and power error through as­pheric compensation for each Rx. This means for each sphere, cylin­der, axis, prism and add power, the patient receives a truly customized lens with an exact Rx for near, an exact Rx for intermediate, and an exact Rx for distance.

Seiko Internal Free-Form lenses are as easy to fit as a conventional pro­gressive lens using a monocular PD while ensuring proper lens height. Be sure to always verify the lens cut-out on every Rx using the fitting and cutout guide.

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