Material
Evidence
The
latest data reveal which lenses and solutions — and combinations thereof
— will help keep your patients in contact lenses. Are you up-to-date?
By Norman Leach, OD, MS, FAAO
How
do we prevent contact lens patients from dropping out? Certainly, we need to pay
attention to the lens materials we're selecting. But no less important are the solutions
we're prescribing and how they interact with different lens materials. And, of course,
we need to recognize that patients respond differently on an individual basis to
all of these combinations.
Let's review
some important information that will help you manage the complexity of your patients'
needs.
FDA Groupings
First, we must
make sure a contact lens wearer has healthy eyes by confirming a normal tear film
and ruling out lid disease, allergy and any other underlying conditions. Then we
can logically select lens materials.
As
you know, the FDA has established the following categories for contact lenses:
Group 1.
Low water (<50%), nonionic
Group 2.
High water (>50%), nonionic
Group 3.
Low water (<50%), ionic
Group 4.
High water (>50%), ionic.
If you select
a material based on these FDA groups, patient history, your examination findings
and your patients' responses to their existing lenses and solutions, you'll have
your best chance of keeping them in contact lenses. However, if the result is less
than satisfactory and you feel a change is in order, remember to switch the patient
to a different lens material group, not just a different brand within the same group.
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Researchers at the University of Waterloo
found no significant differences between Night & Day, Acuvue 2, Proclear and
Dailies when they were worn by symptomatic and asymptomatic patients for 7 hours.1
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Your
primary goal should be to maximize comfort. When striving toward that goal, consider
two important issues: The effects of deposition and dehydration.
Controlling Deposits
Hydrogel lenses,
particularly the high-water types, collect
protein deposits. The use of disposables has decreased this problem significantly,
but it's still a factor. Mucin and lipid deposits are a little less problematic,
but a concern nonetheless. Protein is not such a problem with silicone hydrogel
lenses, but lipids may be an issue. Lipid deposits are much easier to control than
protein deposits, so silicone hydrogel lenses may be best in terms of spoilage associated
with deposits.
Silicone hydrogels
also offer the advantage of maximum oxygen permeability. Night & Day (24% water,
nonionic, Dk/t 175) and Acuvue Advance (47% water, nonionic, Dk/t 60) are available,
and PureVision (36% water, ionic, Dk/t 110) will return to the United States soon.
The newest lens in this category is the O2Optix (33% water, nonionic,
Dk/t 138). Lens parameters for silicone hydrogels continue to expand, and more lenses,
including torics, are on the horizon.
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Nearly
one-half of the contact lens dropouts identified in a survey of 1,500 spectacle
wearers said discomfort was the primary reason they stopped wearing contact lenses.
Discomfort was reported three times more frequently than any other reason for dropping
out. The survey, conducted in 2004 by CIBA Vision, looked at 1,500 patients between
the ages of 12 and 59 and found that 19% were contact lens dropouts.
A
total of 1,444 questionnaires completed at 16 eyecare practices found that 34% of
patients stopped wearing contact lenses at least once because of discomfort, dryness
and red eyes. When asked what it would take for them to resume lens wear, the respondents
said improved comfort and relief from dryness. This survey, representing a 33% response,
was conducted by researchers at the University of Waterloo.
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Dehydration a Factor
All
hydrogel lenses dehydrate at a rate of about 7%, although the rate for silicone
hydrogels may be 2% or less. Even within an FDA group, the amount and rate of dehydration
will differ among materials. However, studies have shown variable correlations between
dehydration and patient symptoms. So we have no fixed guidelines to help us choose
the most comfortable lens based on dehydration.
Within
Group 2 hydrogels, two lenses are reported to be less likely to dehydrate: Proclear
(62% water, nonionic, Dk 34) and Extreme H2O (59% water, nonionic, Dk
21). Other lenses on the market may benefit your patients, but remember to consider
individual response. For example, I've switched a patient from Acuvue lenses to
Proclear lenses to eliminate dryness only to have the patient ask to be put back
in the Acuvue. Morgan and colleagues2 compared Proclear and Acuvue during
200-minute sessions in arid, temperate and arctic conditions and found they provided
equal comfort.
Find the Right
Solution
Another major
factor to consider is how compatible your patients' hydrogels and silicone hydrogels
are with the solutions they're using. Researchers have conducted several studies
of various solutions and lenses, and some have shown complaints of discomfort presumed to be associated
with preservatives and/or surfactants.
In one study,
20 of 39 patients using ReNu Multi-Plus Solution experienced increasing discomfort,
while fewer than five of 39 patients using preservative-free AOSept Clear Care reported
the same problem. The study found that 36% of the patients using ReNu reported end-of-day
dryness, while only 12% of the Clear Care users reported the same symptom.
However,
not all multipurpose solution products are the same. In clinical studies, Opti-Free
Express outperformed ReNu MultiPlus and Complete for end-of day comfort. When measuring
frequency of discomfort during the day, the study found that 18% of multipurpose
solution users reported complaints, compared to 5% of Clear Care users. These percentages
represent patients with complaints every day or most days.
Patients
also can develop inflammatory reactions to some polyhexamethylene biguanide (PHMB)
solutions. You may be familiar with a report of silicone hydrogel interactions with
multipurpose solutions, resulting in extensive staining.3 What's interesting
is that most of these patients were fairly asymptomatic.
When
choosing solutions for your patients, keep all of these factors in mind. The ideal
solution should provide a strong defense against a wide range of microorganisms.
It should be compatible with the ocular tissues and with currently available lens
polymers, including silicone hydrogel lenses. The solution should also be easy to
use and economical for the patient.
Get on Course
I believe we
should lean toward silicone hydrogel lenses or the Group 2 lenses. If a patient
is experiencing discomfort, prescribe a different multipurpose solution, perhaps
one that has a different preservative or hydrogen peroxide, either with his current
lenses or a fresh pair of lenses. If this intervention resolves his discomfort,
then you'll know the solution has been causing the problem. Switching your patient
to one of the solutions, which include enhanced wetting systems, also may make your
patient's lens wear more comfortable.
Dr. Leach
is a clinical professor of optometry at the University of Houston College of Optometry.
He also is director of the Cornea and Contact Lens Service, director of the Cornea
and Contact Lens Residency Program and associate director of the Texas Eye Research
and Technology Center.
References
1.
Fonn D, Dumbleton K. Dryness and discomfort with silicone hydrogel contact lenses.
Eye & Contact Lens. 2003;29:101-104.
2. Morgan PB, Efron
N, Morgan SL, Little SA. Hydrogel contact lens dehydration in controlled environmental
conditions. Eye & Contact Lens. 2004;30:99-102.
3.
Lebow KA, Schachet JL. Evaluation of corneal staining and patient preference with
the use of three multi-purpose solutions and two brands of soft lenses. Eye &
Contact Lens. 2003:29:213-20.
Contact Lens Spectrum, Issue: April 2005