Article Date: 7/1/2003

contact lens management
Tackling Higher-Order Aberrations

Optical Connection presents three new contact lenses using wavefront.
GAROLD EDWARDS, O.D.

As eyecare specialists, we take pride in our ability to refine our refractions to 0.12D sphere, 0.25D cylinder and one degree in axis. Our spectacle prescriptions reflect that refinement. We pay attention to lens base curves, asphericity, thickness, etc. Yet when we turn to soft contact lens fitting, we frequently relax those standards. We might set aside half diopters of residual astigmatism for comfort and convenience. We settle for monovision. We sometimes even set aside our concern for "a perfect 20/20" for comfort and convenience -- ours and our patients'.

Optical Connection's aberration control contact lens

Here's an alternative

Traditional soft contact lenses are designed to correct lower-order optical aberrations (such as spherical power and cylindrical power [and axis] for astigmatism). Until recently, it's been impossible to measure higher-order optical aberrations in the eye -- spherical aberration, coma, trefoil and secondary astigmatism. When left uncorrected, patients often complain of poor contrast, minor "ghosting" of images, night vision reduction and glare.

Researchers in the United States have applied wavefront technology to the development of contact lenses. The result is soft contact lenses with an optimized anterior ellipsoidal surface that reduces higher-order aberrations as well as correcting lower-order aberrations.

Wavefront comes to contacts

Optical Connection Inc. has licensed this patented technology. Incorporated into the proprietary Continuflow moulding process, the company is now producing disposable, blister-packaged aberration-control lenses in three modalities: single vision, toric and multifocal. All are produced in 55% water, methafilcon A blue material.

Aberration control single vision. DefinitionAC ("aberration-control") uses this aspheric, ellipsoidal geometry on its anterior surface. Every power in the DefinitionAC line is precisely designed to provide the maximum aberration-control possible in a molded disposable lens. The higher the minus power, the greater the "aberration-control." The moderately large (14.2), thin draping design with a low tangential edge lift provides the patient with excellent handling, comfort and vision.

Tackling the toric. The DefinitionAC Toric lens uses the same aberration-control geometry as the DefinitionAC lens. The ideal anterior aspheric curvatures for each soft lens power and thickness are incorporated and the lens flexure compensated. This, along with cylinder power correction, results in improved visual acuity at all distances, as well as increased depth of field and improved contrast sensitivity, providing crisper, sharper and clearer vision.

The aberration-control geometry also minimizes cylinder powers by masking up to 1.00D of refractive astigmatism. Toric fitting and stabilization are simplified by the large, thin draping lens design, incorporating multiple thin zone areas. Lens rotation is virtually non-existent, making the DefinitionAC Toric ideal for empirical fitting.

Coming to a multifocal near you. Rounding out the Definition line of disposable lenses is the soon-to-be launched DefinitionAC Multifocal, which incorporates the same aberration-control features and lens design geometry as its companion DefinitionAC products. It's disposable and features a patented presbyopic design which, I believe, mimics natural youthful accommodation and will allow you to reduce reliance on monovision.

DR. EDWARDS IS CONSULTANT TO THE INDUSTRY. YOU CAN REACH HIM AT GLEDWARDS@PRODIGY.NET.

 


Optometric Management, Issue: July 2003