Throughout this informational series on aspheric optics and aberration control, we have focused exclusively on the impact of geometric design on contact lens performance. However, we all know that a variety of factors contribute to successful lens wear, including the lens’ material properties and surface characteristics, as well as the management of patient expectations. In this issue, we will discuss these factors in more detail.

Material Properties

Material properties that directly impact lens wearing health and comfort include oxygen permeability, fluid transport, and material elasticity. Bausch & Lomb PureVision^® lenses, featuring the innovative AerGel silicone-hydrogel material technology, balance the high oxygen transmissibility of silicone with the exceptional fluid transport and elasticity of conventional hydrogel lenses.

With the AerGel silicone-hydrogel material, natural levels of oxygen pass through the lens to the eye, and overnight corneal swelling levels are comparable to levels when no lens is worn. The reduced risk of hypoxic stress helps to maintain excellent ocular health. At the same time, the hydrogel component of the material ensures that PureVision lenses have appropriate physical properties, facilitating fluid transport, allowing proper movement, and encouraging regular tear functions.

Surface Characteristics

Material properties alone do not create a superior contact lens, however. For instance, the silicone components in the otherwise ideal silicone-hydrogel lens material tend to repel tears and attract debris. Research shows that a hydrophilic, consistently wettable lens surface is required for long-lasting comfort and visual clarity, as it resists being coated with tear components and environmental debris.

In the PureVision lens, this was achieved with the Performa surface process. This advanced, proprietary process is a unique application of plasma surfacing technology that "locks" hydrophilic components into the surface of the lens without impeding the flow of oxygen or fluids. In fact, the unique Performa surface process creates an exceptionally smooth and clean lens surface, enhancing comfort while resisting protein and lipid deposits, as shown in the chart below.

The Bausch & Lomb PureVision lens is the only contact lens on the market that combines such advanced material properties and surface characteristics with next-generation aspheric optics, for a precision-balanced lens that delivers exceptional visual acuity and on-eye performance.

The integration of the AerGel and Performa technologies with the PureVision design not only promotes superb vision and comfort, but also encourages longer, healthier lens wear overall with an increased 30-day modality. Clinical studies have indicated that patients respond positively to this wearing schedule, with 82% of patients preferring PureVision for comfort and 86% for vision at this 1-month modality.¹ Eye care practitioners confirmed these findings, responding that the PureVision brand is the most preferred brand in 1-month lens wear altogether.² Collectively, PureVision's design elements are helping doctors improve patient success and compliance.

Patient Management

Without proper management, even the most advanced technologies can fail to meet expectations. Dropout rates remain an ever-present issue in eye care, and over 60% of all dropouts are cited as resulting from unmet vision and comfort needs. The PureVision design helps address these needs, but one-on-one patient management will always be a necessary component for overall patient success.

With any form of visual correction, the right technology must be matched with the right patient, and the practitioner can help patients understand what to expect from the specific correction.

When reducing spherical aberration, it is important to understand that the improvements in vision quality will be subtle under normal lighting conditions. Survey results showed that 92% of doctors recognize that dim or dark lighting increases the negative effects of spherical aberration.³ Therefore, practitioners must appropriately manage patient expectations as to what they will experience and under what circumstances they're most likely to notice improvements.

As shown in the image below, those individuals who drive at night, work in dimmer environments, or have an active nightlife would particularly benefit from such a correction. Also, those individuals with larger pupils (>6mm) are prime candidates.

This is the final issue in our series on spherical aberrations and aspheric optics. We hope that you have found this series useful and informative, and that you now better understand the inherent advantages behind the unique design approach of the PureVision lens.

Remember, not all silicone hydrogel contact lenses are created the same. Understanding the differences can help you give your patients the best lens performance outcomes.

If you missed any issues in this series you can go to our archives on www.bausch.com/enewsarchives. View a video of Mohinder Merchea, O.D., Ph. D., FAAO, discussing spherical aberration and aspheric optics through this link as well.

1. Morely Perspectives on Continuous Wear, July 2001, North America Multi-site Research study 
2. PureVision SVS Comparison Report, 2006.
3. Data on file, Bausch & Lomb.

Brief summary of intended use: The Bausch & Lomb PureVision (balafilcon A) Visibility Tinted Contact Lens is indicated for daily wear or extended wear for up to 30 nights between removals. Warnings: The risk of microbial keratitis has been shown to be greater among users of extended wear contact lenses than among users of daily wear contact lenses. The long-term risk of microbial keratitis has not been determined for this lens. Post-marketing studies are in progress. Precautions: Some patients will not be able to tolerate continuous wear even if able to tolerate the same or another lens on a daily wear basis. Some patients who are able to tolerate continuous wear will not be able to wear their lenses continuously for 30 nights. Patients should be carefully evaluated for continuous wear prior to prescription and dispensing, and eye care professionals should conduct early and frequent follow-up examination to determine ocular response to continuous wear. Side effects: During the one-year US study of the PureVision lens (spherical), 2.9% of the 820 eyes that were fit with the PureVision lens in one eye experienced infiltrative keratitis. Other less serious side effects were mild forms of dryness, discomfort, and burning and stinging. Contraindications: The lens should not be used in the presence of any inflammation, infection, disease, or injury in or around the eye or eyelids that interferes with contact lens wear. The lenses should not be used by individuals who have a systemic disease or an allergic condition that might interfere with contact lens wear. Consult the Package Insert/Fitting Guide for complete information about PureVision contact lenses, available from Bausch & Lomb at 1-800-828-9030 or bausch.com.