The Controversy of Contact Lens Convenience
The Controversy of Contact Lens Convenience
By Jason J. Nichols, O.D.
Can both the patient and the practitioner agree
on which mode of contact lens wear is best? See what each modality has to offer.
Patients love convenience. The more permanent and convenient the mode of visual
correction, the happier patients are.
As doctors, we have an ethical obligation to promote healthy visual correction to our
patients. However, we also want to make our patients happy. Two very convenient modes of
contact lens wear that have become popular among both practitioners and contact lens
patients are daily disposable contact lenses and extended wear contact lenses.
Daily Disposable vs. Extended Wear Contact Lenses
A daily disposable contact lens can be defined as a single-use lens worn up to
one day during waking hours and discarded upon removal. Presently, extended contact lens
wear can be defined as the wearing of contact lenses for 24 hours or longer,
including periods of sleep. Single-use extended wear lenses are used on a weekly basis,
worn for six continuous nights (seven days) and then thrown away. Disposable extended wear
contact lenses were introduced to possibly avoid any ocular health complications that may
be associated with lens aging. As such, there is a key feature which bridges these two
modes of contact lens wear, and that is disposability.
The Food and Drug Administration (FDA) defines a disposable contact lens as a lens worn
only once and then thrown away, never to be worn a second time. Thus, only these two modes
of single-use contact lens wear truly fit the definition of a disposable contact lens.
Daily Disposable Benefits
Disposable contact lenses have been embraced by practitioners who continue to look to
new technology to provide their patients with the most healthy and convenient mode of
visual correction possible. In fact, disposable contact lenses have become the standard of
soft contact lens wear today.
There has been a great deal of discussion about daily disposable lens wear since the
release of the first daily disposable contact lens in 1995, the 1-Day Acuvue (Vistakon).
Market growth continues to increase as other companies have since introduced daily
disposable lenses, including CIBA Vision's Focus Dailies and Bausch and Lomb's SofLens One
Day (Table 1). This competition has lowered costs of this once expensive mode of lens
wear, allowing eye care practitioners to provide the benefits of this mode of lens wear to
a wider range of patients.
Daily disposable contact lenses provide spectacle and RGP wearers the opportunity for
occasional soft contact lens use without the hassles of lens care. The benefits of daily
disposable lens wear include the convenience of disposability, the elimination of cleaning
supplies and regimens, and improved ocular health. Table 2 highlights the advantages of
daily disposable and extended-wear contact lenses.
Extended Wear Contact Lenses: Where They've Been
The extended wear of contact lenses was first described in the literature of the 1950s.
Since that time, the popularity of this mode of lens wear has grown tremendously. In 1979,
the FDA granted its first 30-day approval of extended wear for aphakia, and in 1981, the
FDA approved the cosmetic extended wear of contact lenses for up to 30 days.
However, significant ocular health problems began to arise, and from the doctors'
perspective, the growth of the extended wear of contact lenses was stunted. In 1989, the
FDA repealed the 30-day approval of extended wear lenses and revised its standard to a
six-night, seven-day wearing schedule.
Let's review some of the complications associated with extended contact lens wear.
Hypoxia -- The cornea has very critical oxygen demands that increase with
eyelid closure. With no contact lens wear, the cornea swells on an average of four percent
overnight, but returns to normal within about an hour of open-eye conditions. Even
short-term contact lens wear interferes with the uptake of oxygen and the metabolic
processes of the cornea.
Most currently available extended wear hydrogel contact lenses provide inadequate
oxygen levels to the cornea, maintaining a Dk/L in the range of 10-40. These hydrogel
lenses simply do not meet the standards set forth by Holden and Mertz to reduce or
eliminate corneal swelling. Corneal swelling occurs on the magnitude of approximately 12
percent overnight and four percent during the day with these lens materials.
During extended wear, careful and precise examination of the cornea is required to
detect the clinical signs related to hypoxia, including endothelial changes, limbal
hyperemia, microcysts, neovascularization, striae and vacuoles.
Infection -- The major risk factor for infection with hydrogel contact
lens wear is overnight use. This risk increases with each consecutive night of contact
lens wear. Cases of microbial, fungal and amebic keratitis have all been documented with
extended contact lens wear.
Numerous studies have been conducted which investigate the risk of microbial keratitis
in patients wearing extended wear contact lenses as compared to patients wearing daily
disposable contact lenses. Depending on the study, the increased risk of infectious
keratitis has been found to be between five and 20 times greater with extended wear
patients than with daily disposable lens wear patients.
It is thought that the induced corneal hypoxia leads to an impaired resistance of the
epithelium to microbial invasion.
Inflammation -- Contact lens deposition is another significant problem
associated with extended contact lens wear. A link between lens deposits and ocular
inflammation has also been established with extended contact lens wear. Inflammatory
ocular responses to extended wear include contact lens induced acute red eye (CLARE) and
contact lens induced peripheral ulcers (CLPU). CLARE is characterized by symptoms of
ocular discomfort or pain upon eyelid opening, with redness and photophobia.
Signs of CLARE include: conjunctival hyperemia, subepithelial or stromal infiltrates,
corneal staining and, in severe cases, anterior chamber reactions. CLPUs are sterile
corneal ulcers that are often associated with Staphylococcus aureus.
Extended Wear Benefits
Although the aforementioned complications of extended contact lens wear are serious,
most patients still desire this more permanent and convenient mode of contact lens wear.
As refractive surgery continues to grow, close to one million patients are expected to
undergo this procedure in the year 2000. Although successful refractive surgery is
certainly a convenient mode of visual correction, much of its convenience comes from it
permanency. As such, patients are seeking a convenient and permanent mode of visual
correction. The ultimate contact lens might be considered by some to be a lens that is
worn safely and comfortably, while providing excellent vision without having to be removed
Fortunately, new-generation silicone-hydrogel contact lenses present a promising future
for successful extended contact lens wear. These high-Dk extended wear lenses rely on
silicone for oxygen transmissibility and have nominal Dk/L values of 110 to 175 (which are
certainly above the Holden and Mertz criteria set forth to reduce or eliminate residual
Bausch and Lomb was the first manufacturer to introduce a new-generation extended wear
silicone-hydrogel contact lens, the PureVision contact lens, in the United States (Table
CIBA Vision will also be following suit in the United States soon. With improved oxygen
transmissibility levels, the future of these new-generation extended wear contact lenses
A Forward Glance
Daily disposable and extended wear contact lenses offer many advantages for both the
patient and the practitioner. While both modalities offer convenience, disposability, and
lack of lens care supplies and cleaning regimens, they each offer their own specific
Daily disposable contact lenses offer improved ocular health, but extended wear contact
lenses offer a more permanent, convenient mode of visual correction. As the materials that
comprise extended wear contact lenses continue to improve and patients continue to seek a
convenient and permanent mode of visual correction, the popularity of extended wear
contact lenses will likely grow once again.
Although many practitioners consider both of these modes of lens wear to be convenient,
there are currently no published studies comparing these two modes of lens wear in terms
of patient preference and success. Ongoing studies at The Ohio State University College of
Optometry are examining these issues, and results from these studies will be forth coming.
Dr. Nichols is an advanced practice cornea and contact lens fellow at the Ohio
State University College of Optometry.By Jason J. Nichols, O.D.
Contact Lens Spectrum, Issue: January 2000