Benefits of S-Form Technology

• True aspheric optics with a continuous gradient of power that is truly optical from edge to edge. 
• Greater amount of ADD correction with minimal impact on contrast sensitivity.
•  Usable ADD is contained along a shorter radius of the axial center of the lens in a usable optical area. 
• Produce far greater amounts of ADD correction than is possible with any other RGP manufacturing process. 

S-Form manufacturing vs CnC lathing

Oftentimes it is asked why Computer Numerically Controlled, or “CNC” Lathing, cannot reproduce the aspheric curves and optics created with the “S-Form” manufacturing process. This presentation is not intended to slight “CNC” lathing, but to offer and explanation illustrating how “S-Form” manufacturing has overcome limitations of the former. Although not presented as an exhaustive scientific explanation, it is an attempt to explain differences between the two manufacturing concepts.

“S-Form” manufacturing is a proprietary manufacturing process that allows the compression of more “Effective ADD” correction within a usable optical area at the center of the posterior surface of an RGP lens. Aspheric optics generated by the “S-Form” manufacturing process are part of a family of curves defined as agons, which implies they cannot be mathematically defined. “S-Form” manufacturing creates the aspheric optic with a continuous non-segmented curve from center to edge. The power gradient so derived does not have any optical limitations other than what the visual system can interpret with clarity and the actual fit of the lens on the eye. “S-Form” manufacturing allows for an “Effective ADD” of up to +2.75D, while embracing a corneal alignment fitting philosophy.

In comparison, “CNC” Lathing does not create a true aspheric geometry, but rather emulates an aspheric optic with a series of ever flattening or steepening spherical curves from lens center to edge (“steps and risers”, much like that of a staircase). Given a mathematical equation (i.e. “E” value or series of “E” values) the computer will plot a course machined on the surface of the lens. With sub-micron precision the computer guides the diamond through a series of ever flattening (or steepening) spherical cuts (“steps”).

 
The rise is not a spherical cut, but rather a linear movement of the diamond changing radius length making it longer or shorter to flatten or steepen the curve. The “rise” is accomplished by altering the radius length and ultimately the diamond on the surface of the lens with a linear movement, basically a straight line between point A and B, making it possible to cut a flatter or steeper spherical power. This linear movement does not create usable optics, but is rather a cut made to move to the next flatter or steeper spherical power within a succession or series of different spherical powers. Furthermore, the greater the distance from the lens center, the linear progression of the diamond becomes more and more angled, occupying more and more space within the emulated aspheric curve displacing usable optics and degrading contrast. Higher amounts of asphericity imply more frequent and abrupt non-optical risers than lower amounts of asphericity. All in all, the higher the level of asphericity, and the further away from the center of the lens, the more the rise becomes important to the step.

 
In retrospect: Do all of these successive risers, ever so small and precise may they be, have a deleterious effect on usable optics? In our opinion, yes! Depending on the level of asphericity and the overall size of the optic zone being generated, the accumulative effect of all the linear cuts (risers), eventually compound and create a smaller mount of usable optics. Many will argue that today’s “CNC” lathing offers sub-micron precision and that the human eye cannot detect the non-optical “risers”. However, it is also true that the penny, much as the micron, inconsequential when considered alone, has increasing value if considered within the context of a summation of parts. One million pennies is after all $10,000.00. Just like the eye will, we must focus attention on the entire optical surface being created and not a sub-micron section of that surface.

As to the analogy of a staircase, “steps and risers”, we believe the human eye looks at the total linear drop of the staircase, not the individual steps that compose it. As the linear drop becomes more significant (“Effective Add” greater than +1.50D), optics begin to break down and become unusable to the visual system.

Although “CNC” Lathing is utilized within the proprietary “S Form” manufacturing process, we have not been able to produce optical surfaces that compress as much “Effective ADD” within a usable optical area with “CNC” lathing alone.

If one can see the tree within the forest it’s possible to accept the reality that even sub-micron “CNC” lathing has limitations creating usable aspheric optics with an “Effective ADD” greater than +1.50D while embracing a corneal alignment fitting philosophy.