Comparing the Dry Eye Performance of Two Soft Contact Lenses
BY TAMARA HESTER, O.D.
Dry eye and non-dry eye patients rated comfort, dryness and lens awareness in this one-month contralateral study comparing Focus and Proclear lenses.
Dry eye symptoms are among the most frequent complaints of contact lens wearers, and manufacturers have tried to develop new materials that will reduce these symptoms via increased wettability and decreased deposition. This study compares Proclear (Biocompatibles Eyecare, Inc.), a new lens that promises to provide moisture-retention benefits for dry eye patients, to Focus (CIBA Vision Corporation), an established soft contact lens.
Proclear is manufactured from omafilcon A, a polymer that contains the phospholipid headgroup, phosphorylcholine (PC). According to the manufacturer, the addition of PC reduces on-eye dehydration of the lens and protein and lipid deposition, rendering it more comfortable. Although Biocompatibles' package insert claims an oxygen permeability (Dk) of 33, our calculations based on water content indicate a Dk of 19. The Focus lens, manufactured in vifilcon A material, is a commonly used daily wear lens with a similar water content, diameter and center thickness. The Focus lens has a reported and calculated Dk of 16 (Table 1).
Thirty-one established soft contact lens patients participated in this one-month, single-masked trial. Prior to the first study visit, the patients completed a modified McMonnies dry eye questionnaire. We judged patients who scored 0 to 20 points as not having dry eyes. We placed those who scored 21 points or above in the dry eye study group.
On day zero of the study, we gave the patients new lenses, randomly fitting the right eye with either Focus or Proclear and the contralateral eye with the alternate lens. The examiner was not masked due to the visibility tint of the Focus lens. While the patients knew that they were using two different products, we did not reveal the identity of the lenses or the claims being investigated.
At the dispensing visit, we collected baseline information about the patients' habitual contact lenses, including wearing times, symptoms or problems, comfort and vision. Twenty patients had worn Focus lenses previously, and the habitual lenses of the remaining patients included NewVues, Cibasoft, Illusions and Excelens. We performed slit lamp examinations with and without fluorescein prior to lens insertion.
Upon insertion of the new lenses, the participants rated each lens for comfort, vision and handling using a 0 to 100 analog scale. We evaluated overall fit using the slit lamp. Objective findings included corneal staining, conjunctival staining, high and low contrast visual acuity, overall fit, lens deposition and front-surface, noninvasive tear break-up time over the lenses using a Keeler Tearscope.
We instructed the patients to continue with their current lens care system but to discontinue use of enzymatic cleaners for the duration of the one-month study. The care regimens used included AOSept, QuickCare, PureEyes, Complete Brand, ReNu and Opti-free.
We saw the patients again at one-week and one-month of wear, at which time we performed the same battery of tests. We analyzed the data using multi-way, repeated measures analysis of variance. Thirty patients completed the study; one individual was discontinued after losing the control lens.
At each visit, patients rated the comfort of the lenses on a scale from 0 (painful) to 100 (excellent) upon insertion, at midday, at the end of the day and overall. They reported no significant difference between the Focus and the Proclear lenses at midday or at the end of the day. However, there was a statistically significant preference for the Focus lenses among non-dry eye patients and among all patients combined with respect to initial and overall comfort (Figs. 1 & 2).
NON-DRY EYE PATIENTS AND ALL PATIENTS COMBINED FOUND FOCUS LENSES TO BE SIGNIFICANTLY MORE COMFORTABLE UPON INSERTION.
NON-DRY EYE PATIENTS JUDGED FOCUS LENSES AS HANDLING BETTER.
Patients also rated the handling characteristics of the two lenses on a scale from 0 (very difficult) to 100 (extremely easy to handle). There was a statistically significant preference for Focus among the non-dry eye patients (Fig. 3).
NON-DRY EYE PATIENTS AND ALL PATIENTS COMBINED FOUND FOCUS LENSES TO BE SIGNIFICANTLY MORE COMFORTABLE OVERALL.
Patients reported sensations of dryness and lens awareness as either none, mild, moderate or severe for each eye at the one-week and one-month visits. More non-dry eye patients reported moderate dryness with the Proclear lens, but no statistically significant differences for dryness were found between the lenses among dry eye patients and among all patients combined (Fig. 4).
THERE WAS A STATISTICALLY SIGNIFICANT DIFFERENCE BETWEEN FOCUS AND PROCLEAR FOR SUBJECTIVE DRYNESS AMONG NON-DRY EYE PATIENTS.
More non-dry eye patients and more of all patients combined reported mild and moderate lens awareness with Proclear than with Focus (Fig. 5).
STATISTICALLY SIGNIFICANT DIFFERENCES BETWEEN FOCUS AND PROCLEAR FOR SUBJECTIVE LENS AWARENESS AMONG NON-DRY EYE PATIENTS AND ALL PATIENTS COMBINED.
Patients also rated their visual acuity, but we found no statistical significance.
Corneal staining, conjunctival staining and noninvasive tear break-up time showed no difference overall between the Proclear and the Focus lenses. Based on the noninvasive tear break-up time test used to quantify the lens surface wetting characteristics, both lenses were virtually identical in surface appearance. After 20 minutes of wear, we assessed LogMAR visual acuities with high contrast (98%)/high illumination and low contrast (25%)/high illumination, and found no statistically significant differences. Slit lamp examinations revealed acceptable lens fits and no statistically significant differences in lens deposits.
DRYNESS STILL A CHALLENGE
This study found that comfort with the two lenses was virtually identical among dry eye wearers, while non-dry eye patients rated the Focus lens as more comfortable than the Proclear lens. Objectively, we found no differences in the clinical performance of the two lenses despite a reported dissimilarity in oxygen permeability. Since the two lenses have similar water contents, however, it's not surprising that they perform similarly.
As the population ages and as more people spend more time working at computer terminals, it's likely we'll see more patients exhibiting marginal dry eye symptoms. We can expect that manufacturers will continue designing products to meet the needs of our patients, but it's our duty to determine which products are truly beneficial. CLS
References are available from the editors at Contact Lens Spectrum, or to receive them via fax, call (800) 239-4684 and request Document #25.
This study was supported by CIBA Vision Corporation.
Dr. Hester is in private practice in Atlanta. She is a member of the American Optometric Association, the Georgia Optometric Association and the Greater Atlantic Optometric Association. At the time of this study, she was a contact lens resident at CIBA Vision Corporation.