A Subjective Preference Study of Two Disposable Contact Lenses

BY JOSEPH R. OCCHIPINTI, O.D., ANGELA H. CHAN & BETTY W. LEE
FEB. 1997

In this study, patients compared comfort, vision and ease of use of Ocular Sciences-American Hydron's Biomedics 55 lens with Vistakon's Acuvue lens.

Disposable contact lenses have become the most popular method of vision correction due to better comfort, convenience, health, vision and cost. By disposing of lenses more frequently, patients reduce the risk of eye complications such as infectious keratitis and GPC, and because disposable lenses are usually worn extended wear for one week or daily wear for two weeks, there is a reduced chance for protein buildup or lens contamination.

For our study, we compared Vistakon's Acuvue with Ocular Sciences-American Hydron's Biomedics 55 disposable contact lenses.

METHODS

Seventy patients with healthy eyes who were successful wearers of Acuvue disposable contact lenses participated in this comparison study. All patients wore contact lenses in the minus power range. Two-thirds of the patients wore a base curve of 8.4mm and one-third wore a base curve of 8.8mm.

The Acuvue disposable contact lens is made of etafilcon A and contains 58 percent water. It has a diameter of 14.0mm, center thickness of 0.07mm to 0.11mm for the minus power, 0.12mm to 0.23mm for the plus power and Dk of 28. The Acuvue has a power range of +0.50D to +8.00D in 9.1mm base curve, -0.50D to
-9.00D in 8.4mm base curve, and -0.50D to -11.00D in 8.4mm base curve.

The Biomedics 55 hydrophilic disposable contact lens is made of ocufilcon D and contains 55 percent water. It has a diameter of 14.2mm, center thickness of 0.07mm, Dk of 19.2, minus base curve of 8.6mm and plus base curve of 8.8mm. The Biomedics 55 has a power range of +5.00D to -6.00D, in 0.25D increments.

We dispensed one pair of Biomedics 55 lenses to each patient with instructions to follow their habitual wear schedule and care regimen. After a one- to two-week trial period, we asked the patients to complete a comparison survey (Table 1).

RESULTS

We found that, overall, patients preferred the Biomedics 55 lens over the Acuvue for ease of lens use (Test for Equality of Two Multinomial Probabilities). Fifty-four of the patients preferred the overall handling of the Biomedics 55 (p<0.0001), two chose Acuvue, and 14 felt there was no difference. Fifty-six of the patients felt that the Biomedics 55 lens was easier to detect if inverted (p<0.0001), two preferred Acuvue, and 12 felt that there was no difference between the two lenses. Fifty-one of the patients felt that Biomedics 55 lens was easier to insert (p<0.0001), while two patients chose Acuvue and 17 detected no difference. In terms of ease of removal, 35 of the patients felt that there was no difference between the two lenses (p<0.001), 27 chose Biomedics 55 and eight chose Acuvue (Fig. 1).

FIG. 1: EASE OF LENS USE

Figure 2 shows the patients' preferences based on comfort and vision. In terms of initial comfort, 33 of the patients chose Biomedics 55, while 13 chose Acuvue and 24 felt there was no difference (p<0.005).

FIG. 2: COMFORT, VISION, OVERALL PREFERENCE

To assess comfort over time, we instructed the patients to have been wearing their lenses for a minimum of three hours on the day of the follow-up visit. Thirty-five patients preferred Biomedics 55 for comfort over time, 16 chose Acuvue and 19 felt there was no difference (p=0.005). For better overall vision, 43 responded to 'no difference,' while 21 chose Biomedics 55 (p<0.01) and six chose Acuvue.

When asked which brand of disposable lens they would choose to wear, 63 percent of the patients selected Biomedics 55, 26 percent selected Acuvue and 11 percent chose 'no difference' (Fig. 3).

FIG. 3: OVERALL BRAND CHOICE

DISCUSSION

From this study, we found that the Biomedics 55 disposable contact lens performed better in overall handling in terms of detection if inverted, lens insertion and lens removal. It also performed better in terms of vision, initial comfort and comfort over time. We acknowledge that a change to any new lens could have influenced the patients' responses, although we feel this is highly unlikely based on our past clinical studies of other brands of disposable contact lenses.

Seventy-seven percent of the patients preferred the Biomedics 55 lens for better overall handling, primarily because it was easier to detect if inverted. To better understand why, we performed a physical examination of the two lenses. We found that the Biomedics 55 lens retained its shape better than the Acuvue lens. In addition, we found that the Acuvue lens was easier to tear and it appeared to air-dry on the finger faster than the Biomedics 55 lens.

Fifty-one of the 70 patients felt that the Biomedics 55 lens was easier to insert because it retained its shape better than the Acuvue lens. Patients also preferred the Biomedics 55 lens in terms of lens removal. We felt that the reason for this preference was because the Biomedics 55 lens is made of a less elastic material. Also, the larger diameter of the Biomedics 55 lens may have given the patients more lens to pinch.

The shape retention exhibited by the Biomedics 55 lens may also have allowed better centration and a better fit on the cornea which would result in better overall vision. In many cases, we found that the power was slightly over-minused or higher than that of the Acuvue.

In terms of initial comfort and comfort over time, we found a significant difference between the two lenses, possibly because the Biomedics 55 lens centered better and, in our opinion, did not dry as easily as the Acuvue.

Overall, 63 percent of the patients preferred the Biomedics 55 lens over the Acuvue lens. This study suggests that overall handling characteristics can influence a successful Acuvue lens wearer to switch to another lens.

A similar study by Kenneth Daniels, O.D., was reported in Contact Lens Spectrum ("Evaluating a New Molded Disposable Lens," Dec. 1995). The study involved 30 subjects who were soft contact lens wearers for at least three months. Dr. Daniels compared the Biomedics 55 with an unidentified leading disposable contact lens brand through subjective surveys and clinical evaluations. Our study, on the other hand, was comprised of only subjective surveys of 70 subjects who were regular wearers of Acuvue for at least six months.

In both of the subjective studies, results showed that patients favored the Biomedics 55 in terms of determination of inversion, ease of insertion and general ease of handling. Additionally, we found that patients chose the Biomedics 55 over the Acuvue for: ease of removal, comfort and vision.

We believe that these studies suggest most contact lens patients will prefer the Biomedics 55 lens over the Acuvue lens. CLS

The authors thank Ocular Sciences-American Hydron for supplying lenses for this research study.

Dr. Occhipinti is head of the Student Health Services Eye Clinic, University of California, Irvine. He is in private group practice in Anaheim. Betty Lee attends Southern California College of Optometry. Angela Chan is a graduate of the University of California, Irvine, with a degree in biological sciences.