contact lens focus

A Clarity Rarity

Lens design and optics satisfy astigmatic patients.

Tom Cunningham, O.D.

If you’ve ever fit a toric contact lens, you’re no stranger to the patient complaints of blurry, hazy and fluctuating vision that can accompany these designs. And you’re also, no doubt, well aware of the two primary causes of these complaints: lens rotation and/or inadequate sphero-cylinder correction. What you may not know, however, is that a new toric lens is available specifically designed to address such complaints. It’s called the PureVision2 HD (High Definition) For Astigmatism lens, from Bausch + Lomb.

Here, I describe the lens’ attributes with regard to addressing these complaints.

Auto Align Design

This is a lens-stabilization system comprised of three components: (1) a combination of prism and peri ballasting, which provides clear, crisp reliable vision in extreme conditions, such as during sports and extended computer work, and many environments, such as the office, classroom and theater; (2) a large lens diameter (14.5mm) to provide a big area for effective ballasting and enhanced centration; and (3) a large optic zone (8mm – measurement at center -3.00D – 1.25 x 180), which delivers night and dim-light vision. These components collectively result in both lens stability and orientation, providing uninterrupted crisp and clear vision for several astigmatic patients.

In fact, I’ve had a couple patients in whom I fit the lens remark that the moon is much more “clear” and “defined” for them, whereas in a previous lens it appeared “shadowy.”

PureVision2 HD For Astigmatism
	MATERIAL: Balafilcon A DK/T: 91 WATER CONTENT: 36% WEARING SCHEDULE: Daily wear RECOMMENDED REPLACEMENT SCHEDULE: Monthly BASE CURVE: 8.9mm DIAMETER: 14.5mm POWERS: Currently available: Plano to -6.00D (0.25D steps) - 0.75D, -1.25D, -1.75D with expanded parameters planned later in 2012. 2012: +6.00D to -9.00D (0.50D steps above -6.00D) -2.25D

Corrective optics

The HD optics of the PureVision2 HD for Astigmatism lens decrease spherical aberration across its cylinder and sphere meridians and its entire power range, enabling the reduction of glare and halos in low-light conditions.

In fact, the lens correction is so sensitive that if you forget to compensate for 10° of axis misalignment, the patient may report more blurriness than you would expect. However, once you compensate for 10° of axis misalignment, the patient will likely say, “This is great.” You can really zero in on a prescription, and expect stable vision.

Don’t forget comfort

I would be remiss if I didn’t mention the lens’ comfort-enhancing features. To start, it has a thin edge design to reduce lens awareness. Also, it’s packaged in a moisture-rich solution called poloxa-mine (a moisturizing surfactant) to facilitate lens insertion and initial comfort. Patients often report endof-day and end-of month comfort.

Because the PureVision2 HD For Astigmatism lens is specifically designed to overcome the well-known problems of blurry, hazy, fluctuating vision and inadequate sphero-cylinder correction that can accompany toric lenses, and it delivers a comfortable wear experience, it’s satisfied a large majority of my astigmatism patients. OM