The world of soft contact lenses has
changed very quickly over the past 10 years. As the world of
plastic technology improves and changes, so has the
availability of newer contact lens materials.
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Soft contact
lens plastics have been available in low water, nonionic
polymers, high water, nonionic polymers, low water, ionic
polymers, and high water, ionic polymers. These 4 groups
were created by the FDA to clarify the categories of similar
polymers for investigating solutions. The newest, 5th group
of silicone hydrogel soft lenses are providing a new
material that is providing higher oxygen permeability and
more comfort to a majority of patients who are new fits or
who are being refit with contact lenses. These lenses also
provide improved UV protection.
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Soft lenses were first available for a
patient to use 1 pair that would be used for 1 year.
Sleeping with these lenses was never a consideration. Other
lenses that followed included the
new VUE and Focus lenses that
were manufactured by CIBA VISION (now Alcon). These and
other lenses changed the contact lens market because soft
lenses were now being mass-produced, they were available in
plastic packets, and companies were promoting the safety and
benefits of sleeping in contact lenses. More companies
followed with other soft lenses and the times that were
recommended for sleeping in soft contact lenses varied from
1 week,
2 weeks, monthly, and quarterly.
Sleeping in contact lenses became a great
marketing tool for the various companies. There were some
benefits in sleeping in contact lenses. Solutions were not
required as often reducing the cost to consumers. The
handling of contact lenses became less, reducing the
possibility of infections. But there were other problems.
There was considerable confusion among the public and among
ECPs concerning how long patients should be sleeping in
their contact lenses. Patients, who had been told to use
their soft contact lenses for 2 weeks, were now using them
for 1 month or longer. Patients wanted to reduce the costs
of buying more contact lenses by using them for longer and
longer times. Many patients still believe that there are no
risks to this "overwear" problem.
The problem of patient compliance to a
wearing schedule that was dictated by the FDA, the
manufacturer, and by the ECP was becoming significant. In a
paper published in 1996 by Dr. E. Goodlaw in the
Journal of
Optometry and Vision Science, the problem of sleeping in
soft contact lenses was described:
"Although the risks associated with
extended wear contact lenses are well known, there has not
been an adequate explanation of why sleeping with the lenses
increases the risk of infection. It is contended that the
reduction in the available oxygen caused by contact lenses
does not in itself explain the high rate of corneal
infection caused by wearing the lenses while sleeping. The
results of patient studies show that the risk of ocular
infections, particularly corneal ulcers, is substantially
increased with overnight wear of lenses. A review of the
role of oxygen deprivation, atmospheric pollution, bacterial
survival, infection-resistant defenses, and patterns of
sleep indicates that oxygen deprivation is not the only
factor in increased risk associated with wearing lenses
while sleeping. It is suggested that the combination of the
introduction of airborne pollutants to the contact lens
during the day, the reduced oxygen transmission through the
contact lenses and closed eyelids, and the lack of eye and
eyelid movement during sleep create the conditions in which
bacterial infection is most likely to
occur."
The 1 day disposable soft contact lens
may offer ECPs a way to reduce the risks of
"overwear"
and the hope to eliminate corneal infections. These lenses
are to be used for 1 day only while awake, and then
discarded. The need to use solutions which creates an added
cost is eliminated. Handling lenses is now eliminated with
the possibility of contamination with unclean hands and/or
surfaces. Using contact lens cases is now unnecessary and
they have always been a potential source for contamination
and infection. The opportunity to use a 1 day disposable
lens on an occasional or social basis can now be offered.
The softball player who may have -0.50 Diopter of
uncorrected myopia may find that using this type of lens may
reduce the errors in the outfield. The seasonal allergy
sufferer may also find this type of lens more beneficial for
occasional usage or even during their allergy season. In a
study by Dr. V.Y. Hayes, Dr. C.M. Schnider, and Dr. J. Veys
published in the Journal Contact Lens and the Anterior Eye
in 2003, "of 128 allergy-suffering patients, 67% agreed
that 1 day disposable contact lenses improved comfort when
compared to the lenses that they were wearing prior to the
study."
If you have patients that may have
solution sensitivities, patients that do not want to put
rewetting drops in their eyes, patients that have hygiene
issues, patients that have allergies, patients that have
been unsuccessful with weekly, 2 week, or monthly lenses,
patients that have vision need for occasional use, social
occasions, or for hobbies, patients that have excess protein
buildup, or you have a specific patient that is not
compliant, then the following companies are now selling 1
day soft contact lenses and 1 day toric lenses:
Alcon Vision Care (formerly CIBA) sells
the Dailies Aqua Comfort Plus with a base curve of 8.7 and a
diameter of 14.0 mm. They also have the Focus Dailies with a
base curve of 8.6 and a diameter of 13.8 mm. Bausch and Lomb
has the Soflens Daily Disposable with a base curve of 8.6
and a diameter of 14.2 mm. Clearlab provides the Eyedia
Fresh Daily Disposable with a base curve of 8.6 or 8.7 and a
diameter of 14.0 mm. Cooper Vision sells the Proclear 1 day
with a base curve of 8.7 and a diameter of 14.2 mm.
Preferred Vision Group sells the Preferred Dailies with a
base curve of 8.6 and a diameter of 14.0 mm. Vistakon sells
the 1 day Acuvue Trueye with UV blocking. This lens has a
base curve of 8.5 and a diameter of 14.2 mm. They also have
the 1 Day Acuvue with base curves of 8.5 or 9.0 and a
diameter of 14.2 mm and the 1 Day Acuvue Moist with base
curves of 8.5 or 9.0 and a diameter of 14.2 mm. Orion Vision
Group has the Day Star 1 Day Aspheric with a base curve of
8.6 and a diameter of 14.2 mm. Safigel sells the Safigel 1
Day with a base curve of 8.6 and a diameter of 14.1 mm.
Toric 1 Day lenses are available from Cooper Vision-the
Clearsight 1 day toric, base curve 8.7, 14.5 mm diameter,
Vistakon-the 1 day Acuvue Moist for Astigmatism, base curve
8.5, 14.5 mm diameter, and Bausch and Lomb-the Soflens Daily
Disposable for Astigmatism, base curve 8.6, diameter 14.2
mm.
There should be no reason that any
patient cannot be fit with a soft contact lens or a soft
toric contact lens. Many patients who do have problems with
their comfort have a fitting problem. If the fit is not
exact then vision will be compromised and a patient will not
be happy. There are certainly patients who have comfort
problems based on dryness, protein buildup, or allergies and
there are lenses available that can satisfy these patients.
Some patients may feel more comfortable in the newer
silicone hydrogel lenses. The soft lens must be centered
symmetrically over the cornea and move freely on the bulbar
conjunctiva. There must be adequate movement when blinking
in order to allow oxygen and tears to continue to nourish
the cornea. The various base curves and diameters that are
listed allow the ECP to choose from different base curves
and diameters which will affect the fit, the comfort level,
and the visual acuity of a patient.
If a lens appears to be too tight, the
base curve should be flattened or reduced. Going from a base
curve of 8.5 to 8.6 may improve this problem. The ECP can
also reduce the diameter of the lens to improve the tight
fit or the lack of movement such as changing the diameter of
14.2 mm to 14.0 mm. If a lens is too loose and moves
excessively, the ECP can steepen the base curve such as
changing the base curve from an 8.6 to an 8.5 or increase
the diameter from 14.0 mm to 14.2 mm. Fitting parameters
vary widely for every patient and there are always
exceptions to every rule. If dailies do not fit correctly,
there are many more options available including weekly, 2
week, monthly, and quarterly replacement soft contact
lenses. The other factors that need to be evaluated include
the material, the water content, the optical zone, the
center thickness, the disinfection method, the Dk value, and
the cost.
