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New Device Targets Lens Eversion
BY
MICHAEL FELDMAN, OD
If you currently prescribe silicone hydrogel
contact lenses, then you may have encountered unusual topography findings in some
of your patients. I'll offer a reasonable explanation for these
findings and suggest an easy remedy for their prevention.
New Technology, New Issues
The current revolution in the contact lens industry is wonderful
indeed: Lenses are safer, more comfortable to wear and physiologically more compatible
with the human cornea. They allow eyes to remain whiter, provide superior visual
acuity and can offer a safer, non-surgical visual experience that rivals LASIK.
Indeed, silicone hydrogels may represent the best contact lenses ever.
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Figure 1. Ortho-k-like topography resulting
from everted silicone hydrogel lens wear.
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Figure
2. This patient wore an everted silicone hydrogel lens continuously for one week. |
However, many soft lens patients often wear their lenses inside
out or everted. Reports have emerged and research has confirmed that most patients
can wear modern silicone hydrogels everted without much discomfort, which can cause
significant transient refractive and topographical changes particularly with higher-modulus
materials. The potential also exists for induced contact lens papillary conjunctivitis
(CLPC) resulting from increased mechanical rubbing of the palpebral conjunctiva
when lenses are worn everted. So, in the past, wearing an everted hydrogel lens
was simply an annoyance — but wearing an everted silicone hydrogel lens now
represents a potential for greater complications.
Of course, not every contact lens wearer has an issue with lens
eversion. However, from careful observations I've made in my contact lens practice
over the last few years, I'm now sure this problem is considerably greater than
most of us would ever imagine.
An Unexpected Topography
As a case in point, about two-and-a-half years ago a new patient
came to my practice upset with his previous eyecare practitioner for "not getting
his prescription right." The patient's habitual lenses were silicone hydrogels,
and routine screening topography revealed a map similar to what I had previously
seen only in orthokeratology or post-LASIK patients (Figure 1). The patient denied
any history of refractive surgery or corneal reshaping procedure and frankly, his
–10.00D of myopia corroborated his response. Remaining puzzled and despite
my best efforts at the time, his prescription power continued to fluctuate over
the next few weeks without a history of diabetes or diet change.
Then,
on a routine follow-up biomicroscopic exam, I noticed that the company logo and
code numbers were backwards on his right lens and realized that lens eversion was
the probable cause of his ongoing topographical and visual changes. Equally important
was that the patient experienced no physical discomfort associated with the everted
lens.
I've found this effect to be compounded with higher powers (both
plus and minus) and higher-modulus lenses worn everted during continuous wear. I'm
sure corneal thickness and eccentricity also play a role, but we need further study
to make any such determination.
Not So Uncommon
An undetected everted lens can also affect your fit assessment.
Over-refraction and fit evaluation aren't valid when performed over an everted lens,
especially when it may already have caused a transient refractive change. Yet, many
of us fail to routinely confirm whether patients have applied their lenses correctly.
As I mentioned previously, when worn everted, the higher
modulus of some silicone hydrogel lenses can cause corneal flattening as a result
of an "unintended ortho-k effect," which can result in transient refractive changes.
Figure 2 illustrates the topographical map of a 32-year-old female veteran lens
wearer after she unintentionally wore an everted –7.50D silicone hydrogel
lens in her right eye for one week of continuous wear. She expres-sed no subjective
complaints even though she had a transient reduction of 2.00D of myopia in that
eye. I instructed the patient to remove her right lens at night over the next
several days. Power and topography had returned to baseline at her one-week follow
up.
I've since read several papers presenting similar findings by
others and have conducted hundreds of "mini focus" sessions with my spherical soft
lens wearers asking the following question: "Are you 100 percent sure every time
you apply a lens that it's not inside out?" Not surprisingly, the most frequent
response I received was, "You can usually tell after the lens is applied because
of the way it feels."
However,
many times a patient may apply a lens correctly, but debris may be trapped under
it and the lens feels uncomfortable. The wearer unknowingly attributes this discomfort
to an "inside out" lens. He then removes, flips, rinses and re-applies the lens
(now with no trapped debris), making it feel better than before — with the
assumption that it's now correct.
Also, as I previously stated, unlike hydrogel lenses, most
patients can comfortably wear everted silicone hydrogel lenses.
Because most major manufacturers place small print (logos, codes
or numbers) on the front edge of their soft lenses, including all current silicone
hydrogel lenses, I've been routinely checking for lens eversion during biomicroscopy.
I'm amazed to see just how often patients — especially the silicone hydrogel
wearers — are wearing at least one of their contact lenses everted.
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Figure 3. A CIBA Vision Night & Day
lens through the Lensvue2 viewer. |
Preventing the Problem
Recently, a new combination "viewer/applicator" has become available
that takes the guesswork out of identifying an everted lens. Lensvue2 (Softsert,
Inc.) uses high magnification to make the small print readable. If you look through
the device and the print on the lens reads correctly, then the lens is ready to
apply. Patients can then turn this FDA-approved device around and apply the lens
by gently touching it to the eye.
I designed Lensvue2 for eyecare practitioners and staff as well
as for patients. It's a sanitary means of applying lenses when fitting patients.
I believe it's arguably a cleaner, more professional and modern approach than using
one's finger. It also features a flip-top storage/disinfecting cup that's used with
a multipurpose disinfecting solution to keep the Lensvue2 applicator clean, sanitary
and ready for use.
On the Lookout
In closing, I suggest that you or your staff routinely check your
patients for lens eversion during their visits. In addition, consider educating
your patients to do the same and make Lensvue2 available to them. It has virtually
eliminated the problem of lens eversion in my practice. CLS
Dr. Feldman is in private
practice, limited to contact lenses, in NY. He is a lecturer, author, inventor,
clinical investigator and advisory panel member. He is also president of Softsert,
Inc. and creator of all Softsert products including Lensvue2 available at
www.softsert.com.
Contact Lens Spectrum, Issue: January 2006