MAKING A SPECTACLE

March 15, 2005

Free-form technology virtually eliminates unwanted radial astigmatic error, the most common cause of non-adaptation in patients with presbyopia.

These advances have occurred in virtually every lens type, but most noticeably in progressive no-line multifocal lenses, single-vision atoric lenses, and thin films. These modern spectacle lenses have finally delivered exactly what your patients have been wanting and needing. Here's a look at some of the most advanced lenses in the marketplace.

Progress in progressives Free-form technology is the latest topic in the ophthalmic marketplace. Everyone is excited by the new and innovative lens technology.

Free-form technology virtually eliminates unwanted radial astigmatic error, the most common cause of non-adaption in patients with presbyopia. Traditional progressive lenses use one base curve to cover a number of prescriptions, which will correct power errors with a specific prescription, but yields a compromise with adjacent prescriptions within a given range.

The SOLAOne design allows presbyopic patients the ability to see at various distances without residual image jump (base down prismatic effect), restrictive focal lengths, or demarcation lines. SOLAOne employs aspherical curves across the front surface of the lens (below the major reference point), while at the same time a gradual decrease in the radius of curvature is used from the distance portion to the near area. This results in a lens that has multiple centers of curvature, which allows for multiple focus points.

Exactly what is the progressive corridor? Simply put, a corridor (umbilical line), or gradual increase in plus varying conic sections (curves) from the distance portion to the near portion of a progressive lens, creates additional plus power. As the add power increases, positive radial astigmatic dioptric power (plus cylinder) is introduced in the lens. The result is skewed aberration toward the periphery of the lens.

Traditional progressive lenses have increased residual plus cylinder, which creates the boundary or corridor, which is perceived by patients as a "busy" sensation as their angle of gaze rotates toward the periphery of the lens below the major reference point. Free-form technology helps eliminate excessive unwanted radial astigmatism, which results in a wider intermediate and reading area.

The corridor's length is the distance measured from the optical cross (not the major reference point) to the near optical center. The gradual increase in plus power through the corridor will determine the corridor's overall length. SOLAOne Design by Prescription coupled with free-form technology allows for a wide comfortable reading area with the clearest possible optics for distance.

Cutting-edge single-vision lenses When most ophthalmic professionals want the best single-vision lens for their patients, they consider benchmarks such as the substrates' refractive index, abbe value, specific gravity, and spherical versus aspherical lenses.

One lens design that makes the grade over any other single-vision lens is the VIZIO, which is a linear atoric series of finished single-vision customized lenses with a 1.66n refractive index, with a double-sided anti-reflective treatment.

While aspheric lenses only set out to correct power errors in only one single power in a given plane, VIZIO has an atoric design that optimizes the patient's prescription in every meridian, including tangential and sagittal, which results in perfect optics. The design uses atoric curves on the ocular (back) surface of the lens, with aspheric curves on the front surface, which allows the lens to have a flat plate height/profile without compromising optics. This lens allows your patients to have clear, precise vision in every angle of gaze.