a New-generation Multipurpose Solution
pilot study compares two lens care solutions for corneal staining, lens comfort
and wearing time.
By William Townsend, OD, Sanford Katims,
OD, and Jay S. Rosen, OD, FAAO
& Lomb recently introduced ReNu with MoistureLoc, its new-generation multipurpose
solution. MoistureLoc utilizes alexidine, a small-molecular-weight biguanide, as
a disinfectant. This marks alexidine's first use in a contact lens care product.
It has a history of extensive use as a disinfectant in dentistry.
Small-molecular-weight compounds may gain
entry into the contact lens matrix, and subsequent leaching of the disinfectant
into the tear film during contact lens wear could conceivably cause corneal toxicity
and increased corneal staining.
To investigate this issue and to determine
whether the formulation of the new ReNu with MoistureLoc product eliminated the
staining associated with ReNu MultiPlus, we conducted a brief three-center pilot
study. Our practices are geographically diverse, located in the Northeastern, Southeastern
and Southwestern United States.
The 30 subjects in this study were experienced
Acuvue 2 (Vistakon) lens wearers from our three practices. We selected Acuvue 2
as our test lens primarily because it's among the most frequently prescribed lenses
in the United States. It's a Group IV lens, the most frequently prescribed group
of hydrogel lenses.
We used our computer databases to randomly
select the first 10 adult Acuvue 2 lens wearers. If any of these patients was unwilling
or unable to participate, then we contacted the next patient on the list. We made
no effort to select patients based on previous symptoms, signs or complaints. Participants
received compensation in the form of free lenses at the conclusion of the study.
The patients had used a variety of solutions before participating in the study;
12 had used ReNu/ReNu MultiPlus, 10 had used Opti-Free Express (Alcon), three had
used Complete (Advanced Medical Optics) and two had used store brands. Three had
no habitual solution brand.
The study utilized an open-label, cross-over
design. We did not mask the solutions from observers or participants. We dispensed
new Acuvue 2 lenses to patients for wear on a daily wear basis. We also provided
each patient with either ReNu with MoistureLoc MPS or a control solution, Opti-Free
Express. Opti-Free Express is preserved with Polyquad.
Figure 1. Mean
staining scores for ReNu with MoistureLoc and Opti-Free Express
two weeks of product use, we questioned patients about lens comfort and wearing
time. We then performed slit lamp evaluation and recorded the results on standardized
forms. Patients then received new lenses and were crossed over to the other test
solution. After two weeks with the new lenses and solution, we questioned and evaluated
the participants a second time.
We used slit lamp examination
to assess corneal staining, using a corneal staining template to accurately measure
the area of corneal staining. We also evaluated staining severity. We visually divided
the cornea into five sections (central, superior, nasal inferior and temporal) and
graded staining on a 0 to 4 scale in each section. We then totaled the numbers for
each section in which staining appeared to calculate the area of staining.
We used a 100-point visual analog scale
to rate overall contact lens comfort for each eye. The subjects rated comfort from
"severe discomfort" (0) to "moderate awareness" (60) to "no awareness" (100).
We used a similar scale to rate end-of-day lens comfort for each eye. Rating benchmarks
ranged from "unusable" (0) to "good" (60) to "excellent" (100).
At the conclusion of the study, patients
completed an exit questionnaire in which they compared the performance of the two
study solutions for certain key attributes. For each question patients could indicate
that the solutions were the "same" or they could choose one of the solutions.
Corneal Staining In this study,
corneal staining was greater in patients when using ReNu with MoistureLoc compared
to when using the control, Opti-Free Express. In the majority of patients, mild
staining was confined to one segment of the cornea. The mean staining grade for
ReNu with MoistureLoc was 0.97 compared with 0.52 for Opti-Free Express. The mean
staining area was 1.6 for all segments for ReNu with MoistureLoc while the mean
staining area was 1.2 for all segments for Opti-Free Express (Figure 1).
Macropunctate staining was more frequently
associated with ReNu with MoistureLoc than with Opti-Free Express. Sixteen eyes
(26.7 percent) from patients using ReNu with MoistureLoc had staining grades of
2 (macropunctate) or higher in one or more segments of the cornea. One patient (1.6
percent) using Opti-Free Express had staining of this magnitude.
We calculated a "patient staining severity
score" by multiplying the grade of staining by the area of staining, allowing a
maximum of 20 points per eye or 40 points per patient. Using this calculation, mean
staining severity for the total of two eyes was 5.3 for ReNu with MoistureLoc, while
the mean staining severity score was 2.4 for Opti-Free Express. Six (20 percent)
of the patients using ReNu with MoistureLoc had a severity score of 10 or higher.
One (3.3 percent) patient using Opti-Free Express had a score of 10 or higher. This
patient had a score of 18 with ReNu MoistureLoc and 10 with Opti-Free Express.
Wearing Time Wearing
time was essentially the same for both products and appeared unrelated to staining
severity. Patients had a mean habitual lens wearing time of 13.3 hours before the
study, with a mean maximum time of 16.2 hours. Mean comfortable wearing time during
the study was 13.4 hours for ReNu with MoistureLoc and 13.6 hours for the Opti-Free
Comfort Figure 2 shows
responses to the patient preference questionnaires. The majority of patients found
no difference between ReNu with MoistureLoc and the control solution for comfort
upon lens application, ease of handling, making lenses feel cleaner or better vision.
However, among participants who expressed a preference, a greater number preferred
Opti-Free Express in several categories including overall comfort, keeping lenses
comfortable for longer, ease of handling, better vision and reduced sensation of
We've found that visual analog scales
are an effective way to quantify subjective patient response with minimal test bias.
Ratings on the visual analog scales paralleled our patient preference results. The
average patient rating for overall comfort on the visual analog scales was 78.8
for ReNu with MoistureLoc compared to 84.1 for Opti-Free Express. End-of-day comfort
was rated 74.7 for ReNu with MoistureLoc compared to 81.1 for Opti-Free Express.
Five of the six patients who had staining severity scores of 10 or higher preferred
Opti-Free Express over ReNu with MoistureLoc in the areas of overall comfort and
making lenses feel comfortable longer. The sixth patient rated the solutions the
Figure 2. Staining severity scores for ReNu
with MoistureLoc and Opti-Free Express.
pilot study raises several issues that invite further exploration using a larger
patient sample. We conducted our study using Acuvue 2, a widely prescribed Group
IV lens. We observed staining of grade 2 or higher more frequently in patients using
ReNu with MoistureLoc. Six of 30 patients using ReNu with MoistureLoc had staining
scores of 10 or higher out of a maximum of 40.
Staining has been reported with the
earlier formulation ReNu MultiPlus in silicone hydrogel lens wearers and in Group
II hydrogel lens wearers, with the disinfecting ingredient PHMB suspected as the
primary cause. Like PHMB, alexidine is a biguanide. The results of our study suggest
that alexidine may have some of the same staining issues as PHMB. The small size
of the alexidine molecule (800 Daltons) may allow absorption into the lens matrix,
leading to the notable corneal effects we observed. We're interested to see how
the MoistureLoc solution performs with silicone hydrogel and Group II lenses.
With only 30 patients enrolled, you
should consider this a pilot study. We would strongly recommend subsequent studies
be double-masked. Although our results are interesting, absolute conclusions regarding
comfort preferences require larger patient samples and additional testing. In this
study we failed to observe increased wearing time or better comfort with the new
ReNu MoistureLoc solution despite its claimed benefits.
Five of the six patients who had staining
scores of 10 or above favored the control. This is an intriguing area for follow
up because staining at these levels has been reportedly asymptomatic. Perhaps the
patients in our small sample were more sensitive to moderate degrees of staining
than we anticipated. It's also possible that formulation differences in ReNu with
MoistureLoc may have less impact on corneal sensitivity than other care products
do. Despite numerous studies, the precise relationship between corneal staining
and patient comfort remains poorly defined, but in our small study there was a preference
for Opti-Free Express over Renu with MoistureLoc in patients who had more significant
staining. A larger study could more thoroughly evaluate the statistical analysis
of significant staining and comfort.
Our small multi-center open-label study conducted
in three geographically diverse practices suggests that the use of ReNu with MoistureLoc
in conjunction with wearing Acuvue 2 (Group IV) lenses may be associated with increased
corneal staining when compared to Opti-Free Express, which contains a different
disinfectant. Our study failed to demonstrate increased comfort or wearing time
with the use of ReNu with Moisture Loc. Use of ReNu with MoistureLoc appeared to
correlate with more corneal staining. Additional investigation is warranted to confirm
and further explore the implications of these findings. CLS
This study was funded through Skunk Works
Research by Alcon Laboratories, Inc.
Dr. Townsend is in private practice in Canyon,
Texas, and is a consultant at the Amarillo VA Medical Center.
Dr. Rosen practices in a large general and surgical practice that
provides full scope optometric and contact lens specialty care, medical eyecare
and post surgical care.
Dr. Katims is in private practice in Port Washington, NY,
currently attends Touro College of Law and lectures about silicone hydrogel lenses.
Contact Lens Spectrum, Issue: December 2005