VSP Blog

Conventional ophthalmic lenses might be described in many ways, depending on a person’s point of reference.  Many years ago, while working as a sales representative for a progressive lens company, it was not uncommon to hear people refer to my wares in terms suggesting they were not of the “conventional” variety.  Progressive lens designs, after all, employed sophisticated engineering techniques to create a lens with a gradual increase in plus power so that my lifeblood, the presbyopic population, could enjoy distance to near vision (and everything in between) without lines.  This was still considered cutting edge then, but now generally regarded as “conventional.”

In spite of the fact that progressive addition lenses have been commercially available since the 1950s, with the first patents appearing in the early decades of the 20^th century, they were just gaining noticeable use in the 1980s and 90s.  At this time, the technology used in their design rendered this category of lens a genuine visual benefit versus a mere cosmetic enhancement.  Nevertheless, the model on which progressive designs were created was based on a molded blank containing the aspheric surfaces that induce power change with a back surface traditionally ground to create the actual prescription.  Researchers developed better ways to manipulate the front surfaces through the years through refinements and advancements in engineering technology, but the basic model remained the same.

A more recent development known as “freeform” employs digital surfacing equipment in various ways to create pristine lens surfaces.  Some freeform designs completely customize lens fabrication in accordance with each patient’s individual prescription, facial features, and frame fit.  Others use a traditional blank and produce a perfected digitally fashioned surface on the back.  Freeform lens designs vary in complexity and the degree to which they personalize a lens, but all represent an evolutionary step in the way progressives are fabricated and how they perform.

The foregoing examples have one thing in common, regardless of whether they represent the technology of 1955 or that of 2009, and that is that at any given physical point on the lens, the power is unchanging.  If you gaze through the 90^th meridian, 4 mm below the optical center, the refractive power of your lens, whether digitally surfaced or traditionally surfaced, will always be “x.”  Although progressives are engineered to accommodate natural head and eye movements, some with more precision than others, the optical properties of the lens material is fixed in all cases.

It seems odd to point this fact out, because at one time, I wouldn’t have considered a situation where it wasn’t assumed.  Optics are optics and lens materials were static hunks of glass or plastic.  This paradigm, like so many others that have perished in the wake of progress, is soon to be challenged.  Work is currently underway to produce a lens that is capable of automatically adjusting its optical properties using a combination of electricity, chemistry, and optics.  This lens will change refractive power based on the patient’s gaze, allowing near, intermediate, or distance vision in any lens sector, depending on need.  While not yet released, it feels reminiscent of a science fiction fantasy or clever undercover spy lore.

In no way do I think that “conventional” materials will ever go away.  They work too well and are capable of producing a vast medley of finely crafted optical lenses.  The paradigm that lens materials are static, however, is fading.

File under: Uncategorized, eye health | Tagged: digitally surfaced lenses, dynamic lenses, electric lenses, electro-active lenses, freeform, lenses, progressive lenses, progressives