A Multi-Center Comparison of Two Disposable Lenses

Find out what these six practitioners discovered in their investigation of two disposable contact lenses.

By Drs. Freedman, Miller, Petersma,, Ridder, Rosen & Schiff
MARCH 1999

Good clinicians are constantly on the lookout for new contact lens products that will make their job easier and result in greater safety, convenience and comfort for their patients. In most practices, a newly introduced contact lens is subjected to a mini-clinical trial. Those contact lenses that appear to work well are used frequently, while those that don't seem to perform acceptably are ultimately discarded. The better the contact lens works, the more likely it is to become a mainstay of a doctor's contact lens armamentarium. Unfortunately, given the constraints of clinical practice, the process that doctors use to evaluate new contact lens products, while usually practical, is far from scientific.

Since their introduction less than a decade ago, disposable contact lenses have become the most frequently prescribed contact lens modality. Unlike conventional lenses, that come in a wide selection of parameters, disposable lenses are far more limited. Their limited parameter range, combined with apparent similarities between the different brands of disposable lenses, has encouraged some contact lens fitters to consider disposable lenses to be virtually interchangeable. The purpose of this study was to investigate the relative performance and interchangeability of two leading brands of disposable lenses, Vistakon's Acuvue lens and Ocular Sciences' Biomedics55 lens.

Materials and Methods

Six investigational sites from across the United States participated in this double-crossover comparison study of disposable contact lenses. Each site recruited 10 successful disposable contact lens wearers who had worn disposable lenses for a minimum of six months prior to their recruitment. Inclusion criteria included daily wear for seven days a week and no history of contact lens related complications or wearing problems for two years before beginning the study. No distinction was made regarding the brand of patients' habitual lenses. Test lenses consisted of Biomedics55 8.6 / 14.2 and Acuvue 8.8 / 14.0 in each participating patient's appropriate powers. Each site was provided with investigational lens kits containing six lenses in each power from -0.50D to -6.00D for each brand tested. All contact lenses were rebottled in clear vials under sterile conditions, and their identity masked from both patient and investigator. To reduce the possibility of lens identification due to differential handling characteristics, participating investigators were instructed to have patients insert and remove the contact lenses themselves. In addition, investigators were instructed not to divulge the identity of the test lenses.

To ensure that patient variation in lens fitting characteristics did not affect results, participating patients were carefully selected to conform to manufacturer's fitting range recommendations as published in the manufacturer-issued fitting guides. Patients were instructed to make no changes in their normal lens wearing habits or routines and no changes were made in the patient's habitual lens care system. All patients were on two-week replacement, daily wear schedules and were instructed to remove and clean their lenses nightly. Each participating patient was provided with a new lens care kit at the beginning of the study and were not charged for any of the lenses or examinations during the six-week study period. At the conclusion of the study, all patients received four boxes of their original disposable lens or of their preferred test lens, if in the investigators' opinion, it fit and performed acceptably.

Participating patients completed an entry questionnaire at the start of the study. Questions requiring subjective ratings were based on a five-point scale with one being the least and five being the most. The rating scale is shown in Table 1. The following questions were asked: How many hours a day do you normally wear your lenses? For how many hours do your lenses remain comfortable? Please rate the comfort of your current lenses (1 to 5). Please rate the vision with your current lenses (1 to 5). Please rate the handling of your current lenses (1 to 5). How would you rate your current lenses overall performance (1 to 5)? Patients were examined at the beginning of the study and at two-week intervals, which coincided with lens changes.

History

The following information was collected and tests were performed: visual acuity with original and test lenses during subsequent visits, refraction and overrefraction, K-readings or computerized topography, slit lamp examination with and without fluorescein and slit lamp evaluation of lens fitting characteristics.

After a five-minute equilibration period, lens movement, centration and position were noted. Conjunctival injection, adverse corneal findings (epithelial compromise, microcysts, infiltrates or vascularization) were noted. Any significant adverse response disqualified the patient from further participation in the study. Investigators were instructed to ensure that all test lenses met their usual criteria for adequate lens performance.

At the initial visit and at subsequent visits, test lenses were dispensed with a spare set to be used if a test lens was damaged or lost. As stated earlier, patients inserted their lenses without assistance. In the event that a lens did not fit properly or did not provide adequate visual acuity, it was replaced with a new lens of the same type. If this did not resolve the problem, the patient was discontinued from the study. Lens crossover occurred twice. Patients were divided into two randomly assigned groups. Patients starting with lens A were changed to lens B at two weeks and again back to lens A two weeks later. Patients starting with lens B were changed to lens A at two weeks and again back to lens B two weeks later. Thus, every patient ended up using the test lens he started with.

All patients were provided with a diary and asked to record answers to the following three questions every night: 1) How many hours did you wear your lenses today? 2) For how many hours were the lenses comfortable? 3) Did you have any problems today?

Patients were examined at the end of each two-week wearing period and asked to complete a rating questionnaire, which contained the following questions. Responses were graded on a scale of 1 to 5 with 1 being the least and 5 being the greatest.

1. Please rate the comfort of the test lenses.

2. Please compare the comfort of the test lenses to the last test lenses.*

3. Please compare the comfort of the test lenses to your usual lenses.

4. Please rate your vision with the test lenses.

5. Please compare the vision of the test lenses to the last test lenses.*

6. Please compare the vision of the test lenses to your usual lenses.

7. Please rate the handling of the test lenses.

8. Please compare the handling of the test lenses to the last test lenses.*

9. Please compare the handling of the test lenses to your usual lenses.

10. Please rate the overall performance of the test lenses.

11. Please compare the overall performance of the test lenses to the last test lenses.*

12. Please compare the overall performance of the test lenses to your habitual lenses.

* Questions asked on second and final visits.

The data were analyzed to compare subjective responses to the contact lenses tested as well as to the contact lenses habitually worn by the participating patients.

Demographics

The average age of study participants was 31.5 years. They all wore contact lenses for an average of 9.8 years and had worn disposable lenses for four years. Seventy-five percent of the participants were female. The distribution of disposable contact lenses worn by patients entering the study is shown in Figure 1.

Results

Six sites enrolled a total of 60 patients for this study. Fifty-four patients completed the study. Five discontinued after the first visit, two patients reported comfort problems (both with Lens A), one was discontinued by the investigator because of fitting problems (with Lens B) and two failed to show up for the next visit. One patient failed to show up for the third visit. No adverse reactions were reported or observed during the study.

Participating patients wore each test lens for two weeks before replacing it with the next test set. Investigators were randomly assigned one of two test group protocols. The first group of patients began wearing Acuvue lenses, switched to the Biomedics55 and then returned to the Acuvue for the final period. The other 30 patients began and ended wearing Biomedics and were switched to Acuvue lenses in the middle of the trial.

Wearing Time and Comfortable Wearing Time

Several specific factors were investigated. The length of time that participants wore test lenses was recorded and compared to the length of time that they habitually wore their own contact lenses prior to entering the study. Total wearing times varied between 14.8 and 14.5 hours for entering patients. This small variation was not unexpected, since overall wearing time is more likely a function of necessity or habit than of comfort.

When we asked patients to record the length of time that their habitual contact lenses remained comfortable, the Biomedics55 provided an average of 13.5 hours of comfortable wear while the Acuvue wearer reported discomfort after 13 hours. Overall, the average wearer achieved 12.8 hours of comfortable wear. Wearing times during crossover testing were slightly less than most patients achieved during normal contact lens wear. Patients wearing Acuvue test lenses reported 13.1 total hours, with 12.0 being comfortable. Biomedics55 test wearers reported 13.7 total hours, with 12.4 being comfortable. The average wearing time for all contact lens wearers prior to entering the study was 14.5 total hours, with 12.8 being comfortable.

Lens Comfort

Overall, 56 percent of patients found the Biomedics55 to be more comfortable than either the Acuvue or their habitual lenses. Compare this to 25 percent of Acuvue wearers who found the Acuvue more comfortable. On average, patients rated the comfort of the Biomedics55 a 3.8 out of 5. In contrast, patients gave the Acuvue a 3.2 rating. Patients rated their habitual lenses 3.5.

In a separate question, particicpants were asked to compare on a 1 to 5 scale (1=much worse, 2=worse, 3=same, 4=better, 5=much better) the test lenses they were currently wearing to the other test lenses (i.e. Biomedics55 compared to Acuvue or Acuvue compared to Biomedics55). When patients were asked to compare the comfort of the Biomedics55 to the Acuvue, the rating was 3.7. However, when asked to compare the comfort of the Acuvue to the Biomedics55, the rating was 2.8.

Interestingly, when the subjects were then asked to compare the comfort of the Biomedics test lenses to their habitual lenses, the rating was essentially equal -- 3.1. But when asked to compare the comfort of the Acuvue to their habitual lenses, the Acuvue was rated less comfortable -- 2.6. This comfort difference helps explain why 80 percent of wearers who entered the study wearing Biomedics55 found the Biomedics more comfortable at the conclusion of the study while only 43 percent of wearers who entered the study wearing Acuvue felt that their lenses were more comfortable.

Vision

Both the Biomedics55 contact lens and the Acuvue contact lens are reported to have excellent optical qualities. There was relatively little difference between the Acuvue and the Biomedics55 in visual performance. Biomedics55 scored 3.7 while the Acuvue was rated at 3.6.

When asked to compare their vision with the test lenses that they were currently wearing to the previous test contact lenses, Biomedics55 compared to Acuvue was rated 3.3 while the Acuvue compared to the Biomedics55 was rated 3.2.

When asked to compare the test lenses to their habitual lenses, the Biomedics55 and Acuvue were scored 3.0 and 3.0, respectively. Interestingly, while 100 percent of Biomedics wearers preferred the vision with those lenses compared to the (other) test lenses, only 61 percent of Acuvue wearers expressed a preference for their own lenses at the conclusion of the study.

Lens Handling

Lens handling characteristics can be a major factor in patient success and satisfaction; especially those wearing lenses on daily wear schedules. The Biomedics55 was clearly preferred for lens handling. Patients rated it an average of 3.8 or very good compared to the Acuvue, which earned a 2.7. The Biomedics55 was rated better that patient's habitual lenses, which earned an average of 3.3.

When asked to directly compare the Biomedics55 to the Acuvue, it ranked 3.9 (much better) compared to the 2.4 (worse) when patients compared the Acuvue to the Biomedics55. Comparing the two lenses to their habitual lens, the Biomedics55 was rated slightly better by patients at 3.4 while the Acuvue somewhat worse at 2.5. One hundred percent of those who entered the study wearing Biomedics55 preferred it for lens handling while only 35 percent of those who entered the study wearing Acuvue preferred the handling of their lenses.

Overall Lens Performance

Patients were asked to subjectively rate the overall performance of their lenses. Ratings for the Biomedics55 were consistently higher than for the Acuvue or the patients' original disposable lenses. Biomedics55 were rated 3.7 while Acuvue scored 3.0 for overall performance. When compared to the previous test lens, the Biomedics scored 3.7 compared to 3.0 for the Acuvue. The Biomedics were also judged better overall than the patients' habitual lenses with the Biomedics scoring a 3.2 rating to the habitual lens' 2.7 (Fig. 2). One hundred percent of those who entered the study wearing Biomedics55 felt their lenses were the best performing compared to 48 percent of those who entered wearing Acuvue.

Lens Preference

At the conclusion of the study, while the identity of the test lenses remained masked, patients were asked which of the two test lenses they preferred or whether they preferred their habitual lenses over the test lenses. Fifty-nine percent of participating patients expressed a preference for the Biomedics55 over the Acuvue while only 24 percent preferred the Acuvue. Seventeen percent preferred their original lenses (distributed among Nuvues, Seequence, Surevue, Biomedics 38 and others). While 100 percent of wearers who entered the study wearing Biomedics55 wearers wanted to continue wearing their lenses at the conclusion of the study, only 52 percent of wearers who entered the study wearing Acuvue wanted to continue wearing their Acuvues.

Discussion

The primary focus of this study was to examine patient preference and response to two leading brands of disposable lenses. Subjective patient factors are critical to the success of a contact lens. The best lens in the world will never be worn if the patient does not like it. Several recent studies have found that the Biomedics55 is clearly preferred by most patients when they are given a choice between it and other disposable contact lenses. Kenneth Daniels, O.D. compared the Biomedics55 to an unspecified leading disposable lens. Of patients who expressed a preference, 44 percent preferred the Biomedics while only four percent preferred the comparison lens. Daniels also evaluated several other subjective and objective areas of lens performance. He found little difference in the clinical performance of the two lenses. However, in every case where patients expressed a preference, the Biomedics55 was more highly rated than the comparison lens. Joseph Occhipinti, O.D. and associates performed an unmasked comparison of the Acuvue and the Biomedics55. In this study, seventy successful Acuvue wearers were fitted with Biomedics55 lenses. They were asked to follow their usual wearing schedules and to use their regular care products. Overall, 63 percent of the patients preferred the Biomedics55 to the Acuvue. Darwin Morman, O.D. recently reported similar preference in an unmasked in-office evaluation of lens preference among his patients. The present investigation found that 59 percent of subjects preferred the Biomedics55, which is consistent with prior studies.

In our study we also compared the Biomedics55 to the Acuvue. However, we used a masked, controlled design to reduce possible examiner or patient bias. At the time this study was conducted, the Acuvue inversion indicator had just been introduced and all tested Acuvue lenses had this feature. Because it was so new, patients could not associate it with Acuvue brand, but some patients did note its presence. Test lens parameters were limited to 8.6 base curve, 14.2 diameter for the Biomedics55 and 8.8 base curve and 14.0 diameter for the Acuvue. The Biomedics55 is available in two base curves while the Acuvue comes in three. To ensure appropriate patient selection, manufacturers published fitting criteria were adhered to in selecting subjects.

To help understand the significance of our findings, we investigated what factors patients considered important lens qualities. Interestingly, subjective performance characteristics of lens comfort, clarity and handling were rated highest by patients. Lens safety and doctor recommendation were of less influence and lens cost was surprisingly unimportant to most patients. As might be expected, patients rate their lenses on subjective measures such as comfort and convenience. Practitioners need to be acutely aware of how wearers evaluate satisfaction with their lenses and the practitioners who fit them.

A rating scale was developed and used to evaluate subjective measures of lens performance. The use of a rating scale provided a more detailed analysis of subjective response. The Biomedics55 was chosen superior to the Acuvue and to their own habitually worn lenses (by patients who wore other brands) in all measured areas of lens performance; however, the performance differences were most notable in lens handling and comfort. The importance of lens handling is often overlooked by many clinicians, however, its relevance as an issue was clearly evident among the participating patients. Because patients experience lens handling difficulty in the privacy of their homes, any problems remain hidden except in only the worst cases. It is likely that lens handling difficulty is a major unrecognized source of frustration for many patients and may be an important factor in contact lens dropout.

Lens comfort is also difficult to objectively evaluate in most clinical settings, yet was rated as the most important lens quality. Most patients are fitted with only one lens and do not have a basis for comparison. They endure discomfort because they do not know it could or should be any better. Contact lens discomfort may also be an important but well hidden factor in contact lens dropout. Patients rated the comfort of the Biomedics55 as superior to the Acuvue and to most other brands that they habitually wore. Superior comfort ratings were correlated with longer wearing times and longer periods of comfortable wear.

Perhaps the most telling response that we obtained was that of final lens preference. At the conclusion of the study, more than twice as many patients preferred the Biomedics55 compared to the Acuvue. Additionally, more than three times as many preferred the Biomedics55 compared to their habitual lenses. When looking at specific lens performance factors, almost all of those who entered the study wearing Biomedics55 preferred their habitual lenses while significant numbers of those who entered wearing Acuvue preferred the Biomedics55. This suggests that while the Biomedics55 is very interchangeable with other brands, Acuvue seems to have some limitations in this area.

Conclusion

Many factors determine contact lens quality and performance. Clinicians are concerned about issues such as biocompatibility, oxygen permeability, lens fitting characteristics, range of available parameters, lens stability and resistance to buildup. Patients concerns include comfort, ease of lens handling, wearing time, longevity, cost and safety. Lenses available in the United States undergo extensive investigation and must meet strict clinical performance standards before receiving FDA approval. This approval process produces generally excellent products with adequate clinical performance profiles. The Biomedics55 is one of several quality disposable contact lenses currently available. However, in every measure of patient satisfaction the Biomedics55 was found superior to other brands.

In selecting the best contact lens for a patient, clinical concerns are important. However, the patient ultimately decides whether a contact lens is a success or a failure. They also make decisions about whether to continue contact lens wear and how they perceive the clinician that fitted them. Our results suggest that patients may be more concerned about how lenses feel and function than they are about issues that may be more important to contact lens practitioners, like lens safety and oxygen transmissibility. Since patient satisfaction may be the single most important factor in the ultimate success of both patient and practitioner, it is critical that clinicians evaluate contact lenses from the patient's perspective. Despite the apparent similarities among disposable contact lenses, this study strongly suggests that our patients may be more aware of the differences between brands than we are.

Joseph M. Freedman, O.D. is a partner in a group practice in Roslyn, New York.

Joan P. Miller, O.D. is in private practice in Hillsboro, Ohio.

Jay D. Petersma, O.D. has been in private practice in the Des Moines, Iowa area for the past 10 years.

Tim R. Ridder, O.D. practices in a partnership in Hutchinson, Kan.

Jay S. Rosen, O.D. practices in Ft. Myers, Fla.

Harold Schiff, O.D. has been in private practice for 22 years in Riverview, Mich.

TABLE 1: Ratings scale used to determine patient subjective response.