Contact Lens Design & Materials
When Lenses are Improved, Patients Benefit
By Neil Pence, OD, FAAO
Taking existing products and improving them is common, and this certainly is true in the contact lens field. In the past six months, two silicone hydrogel contact lenses have been reintroduced slightly revised. We will look at what changes occurred and provide examples of how the changes have impacted patients.
The Acuvue Advance (Vistakon) spherical lens was upgraded to become the Acuvue Advance Plus contact lens. Only small modifications were made in the material, thus not requiring new FDA approval. Slight changes to the processing of the lens, perhaps in the basic material mix and/or optimizing the curing process in some manner, have resulted in a surface that is more resistant to deposits. Vistakon is positioning this lens as an economical two-week replacement daily wear option and has introduced 24-packs as a further cost savings that may encourage compliance as well.
Bausch + Lomb (B+L) has introduced the PureVision2 HD (PV2 HD) contact lens, which is a modification of the original PureVision spherical lens. The lens material remains unchanged, again not requiring new lens application and approval. The new design has a roughly 20-percent thinner profile, which may impact comfort as well as provide increased oxygen transmission. A wetting agent has also been added to the lens package to enhance initial on-eye comfort. As with the original PureVision, the PV2 HD incorporates spherical aberration correction into the lens.
“New and improved” always sounds good, but in the case of contact lenses, how does it help the patients wearing them? Although the lenses are fairly new and experience-limited, the following cases may be of interest.
Patient #1 A graduate student reported for her annual visit. She had worn Acuvue Advance lenses for the past four to five years with no complaints about her vision or contact lenses. We switched her to Acuvue Advance Plus in the exact parameters as her previous lenses. She returned for dilation nearly six weeks later and reported that the new lenses “seemed slicker” when she removed them compared to her previous lenses. She had not changed her disinfecting solution and reported rubbing “some nights,” but not most. Presumably, the lens was depositing less and maintaining a more moist surface.
Patient #2 A 16-year-old had worn PureVision lenses for one year with no complaints. Our intern was ready to re-order when a slight hazy arcuate area was detected in the superior cornea OD, suggestive of past epithelial split episodes. Upon questioning, the patient reported five to six incidents of irritation or feeling “like a hair was under my lens” during the past year. She was refit into the PV2 HD lens, and has experienced no recurrences in the subsequent five months.
Patient #3 A 17-year-old had been refit in our clinic, but with limited success. We fit his previous brand, PureVision, in the same −12.00D power as before, with visual acuities of 20/30 and 20/30−. We then fit the PV2 HD to increase oxygen, and his VAs improved to 20/25+ in each eye. We don't know whether the optics were changed or whether the thinner lens happens to perform differently in this case, but extremes in power might be where such differences would occur.
Revising and improving existing products certainly happens in contact lens materials and design. When this upgrading in performance occurs, patients are the ones who ultimately benefit. CLS
Dr. Pence serves as executive director, Clinical and Patient Services, Indiana University School of Optometry in Bloomington, Ind. He is a consultant or advisor to B+L, Ciba Vision, and Vistakon and has received research funding from AMO. You can reach him at email@example.com.