Article Date: 9/1/2012

Better Optics Deliver Clear, Consistent Vision

Better Optics Deliver Clear, Consistent Vision

Learn how the PureVision2 family can satisfy patients and help build your practice.

By Agustin Gonzalez, OD

In the past, both spherical and toric contact lens patients often had to accept some compromise in clarity of vision or comfort in order to wear soft contact lenses. Indeed, a recent survey of patients who wear toric soft contact lenses found that complaints of blurry, hazy, distorted and fluctuating vision were common and bothersome for this population.1

Recently, Bausch + Lomb developed PureVision2 and PureVision2 For Astigmatism lenses. Both have aspheric optics to deliver clear, consistent vision while reducing halos and glare in low light. The aspheric optics are the result and convergence of improved optics, better understanding of on-eye lens performance, and the use of sophisticated manufacturing. These products have given my practice a high performance vision product with a fast-fitting toric alternative to the current lens designs.

IMPROVED OPTICS

Spherical aberration occurs as light that travels through the periphery of the lens focuses at a different point from the light that travels through the lens center (Figure 1). A mean spherical aberration of +0.18 µm has been reported for myopic eyes,2 so understanding the interaction between cornea and contact lens is crucial to developing a product that performs better on eye. Spherical aberration can have a negative effect on quality of vision and is pupil size dependent. Larger pupil size increases the spherical aberration effect, which in turn negatively affects visual clarity and contrast sensitivity.

Figure 1. With spherical aberration, light rays passing through the center and periphery of the optical system do not simultaneously focus at the same focal point.

When developing the PureVision2 family of lenses, Bausch + Lomb researchers used sophisticated computer models to study contact lens conformance to the eye and the optical impact in both the central and peripheral cornea. The uniqueness of this family of lenses is the fact that Bausch + Lomb devised a way to maintain a spherical aberration compensated lens. The large optical zone maximizes the optical benefit from this aberration reduction, most notably in low-light conditions. The PureVision2 For Astigmatism lens also reduces spherical aberration on both the cylinder and spherical meridians of the lens.

GREAT STABILITY

The stabilization of PureVision2 For Astigmatism, Auto Align Design, uses thick and thin zones creating a hybrid-ballasting design that incorporates stability characteristics of a prism ballast and two peri-ballast areas (Figure 2). The design was the result of studying blink mechanics and cornea-contact lens interactions. The result was minimal rotation, quick alignment into position, and phenomenal stability. In addition, the lens design is comfortable and delivers consistently clear vision to patients. A large lens diameter (14.5 mm) along with the 8.9-mm base curve, also aids in maintaining both centration and stability.

► ► DEMONSTRATING SUCCESS

CASE 1
The patient, a 32-year-old Hispanic male, had used toric lenses in the past but reported being unhappy with the quality and stability of vision.

■ Rx
OD: -1.00 -2.00 X 170 20/20+
OS: -4.75 -1.50 X 030 20/20+
■ Keratometry
OD: 45.25/45.75
OS: 44.75/45.50
■ Pupils
OD: 4mm photopic pupil
OS: 4mm photopic pupil
■ Fitted with PureVision2 For Astigmatism
OD: -1.00 -1.75 X 170 8.9 14.5 20/20+
OS: -4.50 -1.25 X 030 8.9 14.5 20/20+

The patient reported great stability of vision and mentioned that there was less glare when driving at night.

CASE 2
The patient, a 21-year-old white female, had used contact lenses before but reported some difficulty driving at night.

■ Rx
OD : -7.00 -0.25 X 120 20/20
OS : -7.55 -0.50 X 080 20/20
■ Keratometry
OD: 44.25/44.50
OS: 44.25/44.25
■ Pupils
OD: 6mm photopic Pupil
OS : 6mm photopic Pupil
■ Fitted with PureVision2
OD: -6.50 20/20+
OS: -7.00 20/20+

The patient reported improved night vision. The aspheric optics combined with the larger diameter provide great optical performance for patients with larger pupils and moderate to higher prescriptions.

Figure 2. The Auto Align Design, a dual-ballasting system, keeps the lens from rotating out of position. It employs both prism-ballast and peri-ballast systems.

ENHANCED COMFORT

For added comfort, the PureVision2 family of lenses incorporates a thinner edge profile than the original PureVision lenses. The edge is also rounded to allow for a smooth transition between the lens and the conjunctival tissue.

The balafilcon A material is the same silicone hydrogel polymer used in the original PureVision contact lens. It has 36% water content with a Dk of 99 (Dk/T of 130 at center [-3.00 D]) which allows for a high degree of oxygen permeability.

ACCEPTANCE AND SUCCESS

My clinical experience with the PureVision2 family of lenses has been extremely positive. The toric lens stabilizes quickly on the eye, making the initial fitting process easy for my technician. Initial rotation of the lens is minimal and could be compensated in the same visit, rather than requiring a follow-up appointment. This makes my work more efficient and less complicated. In addition to ease of fit, the lenses provide crisp visual acuity for my patients. There is a high degree of acceptance and satisfaction among patients fitted with the PureVision2 family of lenses.

DR. GONZALEZ OWNS TWO PRIVATE INDEPENDENT OPTOMETRY PRACTICES IN THE DALLAS AREA. HE HAS A SPECIAL INTEREST IN THE USE OF SOCIAL MEDIA AND INTERNET MARKETING AS WELL AS CHANGING TRENDS IN MEDICATION USE BY OPTOMETRISTS. DR. GONZALEZ IS A FREQUENT LECTURER AT OPTOMETRY MEETINGS. HE IS AN ADJUNCT FACULTY MEMBER AND GRADUATE OF INTER AMERICAN UNIVERSITY SCHOOL OF OPTOMETRY IN PUERTO RICO.
HE SERVES AS A COUNCIL ON OPTOMETRIC PRACTITIONER EDUCATION REVIEWER FOR THE ASSOCIATION OF REGULATORY BOARDS OF OPTOMETRY AND ON THE EDITORIAL BOARD FOR PRIMARY CARE OPTOMETRY NEWS. DR. GONZALEZ IS A CONSULTANT/ADVISOR TO ALCON, ALLERGAN, BAUSCH +LOMB AND ISTA.

REFERENCES

1. Mack CJ, Rah MJ. Visual benefits of highest importance to eye care professionals and patients when choosing contact lenses for astigmatism. Poster presented at AAO 2011.

2. Cox I, Kingston A, Vogt AKS. Wavefront aberrations of the human eye — a large population study. Poster presented at annual BCLA meeting; Manchester, UK; 2011.



Contact Lens Spectrum, Issue: September 2012, page(s): 3 4