Article Date: 5/1/2008

Honed Comfort Zone
contact lens management

Honed Comfort Zone

Silicone-hydrogel provides low modulus and high wettability.

BURT W. DUBOW, O.D., F.A.A.O.

Several patients fit in the first generation of silicone-hydrogel lenses experienced superior epithelial arcuate lesions (SEAL), giant papillary conjunctivitis (GPC), conjunctival staining, adaptation difficulty when switching from traditional soft lenses and dry eye.

I learned that many of the cases of SEAL, GPC, conjunctival staining and adaptation difficulty were associated with the high modulus of the materials, which don't drape well on the cornea.

The high modulus of these first silicone-hydrogel lenses wasn't the only cause of adaptation difficulty, however. Despite the plasma coating or plasma oxidation surface treatments the contact-lens manufacturers used to cancel out the hydrophobic (water-fearing) characteristic of these lenses, several patients reported lens-related dryness.

Thankfully, contact-lens manufacturers have since offered several lower modulus and wettable silicone-hydrogel designs. The latest offering: Avaira, from CooperVision.


Aviara
MATERIAL: Enfilcon A
WATER CONTENT: 46%
DK/T: 125
WEARING SCHEDULE: Daily wear
RECOMMENDED REPLACEMENT SCHEDULE: Two-weeks
DIAMETER: 14.2mm
BASE CURVE: 8.5mm
SPHERE POWERS: -0.25D to -6.00D
PATIENT COST: $25 to $30

Low modulus

Avaira — a hybrid of the Italian word "avanti," meaning "ahead" or "forward" and the English word "air"—is a two-week replacement lens that provides a modulus similar to a traditional hydrogel lens (0.5MPa). This means that patients who wear this lens are less likely to experience the ocular issues and adaptation problems associated with the first-generation high-modulus silicone-hydrogel lenses.

On a personal note, I considered upgrading my compliant two-week wearers of the older silicone-hydrogel and hydrogel-lens materials to the Biofinity (CooperVision) silicone-hydrogel lens. CooperVision introduced this lens, which offers a low modulus of 0.75MPa and high-oxygen transmissibility via its dk/t of 160, last year. Because Biofinity is a monthly replacement lens, however, I feared that altering the replacement schedule for these patients could lead to noncompliance. The recent introduction of Avaira has enabled me to comfortably switch my two-week replacement wearers.

Wettability

CooperVision has manufactured Avaira from enfilcon A, a naturally wettable material, which benefits from the company's patented Aquaform technology. This technology uses hydrogen bonds to lock water into enfilcon A, allowing the lens to retain water or tears throughout the day. This means that patients who wear this lens have less of a chance of experiencing lens-related dry eye. In fact, those patients who I've switched to Aviara have commented that it's comfortable all day with little to no feeling of end-of-day dryness.

I choose to offer Avaira to my two-week replacement lens wearers because it offers low-modulus properties in a highly wettable, dehydration-resistant and high-oxygen material. Two added features: an ultra-violet ray blocker and an aberration-neutralizing system, which employs aspheric optics to minimize spherical aberrations inherent in both the lens and human eye. OM


DR. DUBOW IS IN PRIVATE PRACTICE IN ST. CLOUD, MINN. HE IS A CHARTER MEMBER AND PAST CHAIR OF THE AMERICAN OPTOMETRIC ASSOCIATION'S CONTACT LENS AND CORNEA SECTION. E-MAIL HIM AT BDUBOW@INSIGHTEYECARE.US.

Optometric Management, Issue: May 2008