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REVIEW
Cover
Focus
Refractive Surgery
Presbia’s Flexivue Microlens creates multifocality with a ring that has
refractive power surrounding a plano central region.
extreme multifocal, which
could cause significant
glare at night, and it’s not
a full monovision, which
could cause binocular disparity.
So it seems to fit in a
sweet spot, with a mixture
of a little monovision and
multifocality. That makes
it very well-tolerated.”
Gustavo E. Tamayo,
MD, director of the Bogota
Laser Refractive Institute
in Bogota, Colombia
says he has implanted the
Flexivue inlay in 75 patients.
“I use it only in pure
emmetropes, defined as
those with ±1 D of sphere and ±0.75
D of cylinder,” he says. “It’s mostly being
implanted in Europe, where it has
the CE Mark, and South America, but
it’s still not widely used; maybe 1,000
have been implanted in total.”
Dr. Maloney notes several differences
between the Kamra and Flexivue
inlays. “The Kamra inlay improves
reading vision by using pinholes to
increase the eye’s depth of focus,” he
says. “The Flexivue is a refractive inlay;
it improves depth of focus by altering
the path of light rays to the cornea.
It doesn’t block out the peripheral
light rays as the Kamra inlay does.
“Regarding the reduction of incoming
light caused by the Kamra, one of
the interesting things for me has been
that patients are not complaining that
their vision is dark at night,” he adds.
“There may be a couple of reasons for
that. First, we only implant in one eye,
so the other eye is normal. Second, the
Kamra inlay is about 3.8 mm in diameter,
so when the pupil dilates at night
light enters the eye around the outer
edge of the inlay. It may be that those
two factors together keep people from
experiencing dim vision at night.”
Dr. Tamayo says the main advantage
the Flexivue has compared to the
other inlays is its more physiologic approach
to correcting near vision. “Unlike
the pinhole mechanism of action
used by the Kamra inlay, it provides
an optical correction depending on
the refractive defect present,” he says.
“The other advantage is the fact that it
does not have any issues regarding the
distribution of nutrients, which can be
a factor with the Raindrop and Kamra
inlays. Also, the learning curve is very
small; performing the surgery is simple,
fast and easy. Certainly one or two
days of training would be sufficient.”
Flexivue in Practice
Dr. Maloney says the Flexivue could
in theory be combined with LASIK.
“You’d make a flap, correct the refractive
error, place the inlay and then
replace the LASIK flap,” he says. “Or
it could be used with a SMILE-type
procedure, in which you’d remove a
lenticule through a stromal tunnel to
correct the refractive error and then
insert this inlay through the same stromal
tunnel. But I don’t know if that’s
been tried yet. Right now we’re implanting
it in people who are close to
emmetropia. We’re not doing simultaneous
correction of refractive errors.
“In the trials, we’re using a pocket,
not a flap,” he continues. “In a normal
emmetrope we make a pocket with
a femtosecond laser, a channel from
the central cornea to the
peripheral cornea with an
opening in the periphery.
The surgeon grasps the inlay
with a special forceps
and gently slides it into the
pocket, centers it over the
corneal light reflex and releases
it, the same way the
Kamra inlay is inserted.”
As far as contraindications,
Dr. Tamayo says
those would include the
patient being unable to correct
to 20/20 at near, whatever
the reason. “Dry eye is
not affected by the inlay, so
it’s not an issue,” he adds.
Dr. Maloney notes that a full list of
contraindications has not been developed
so far. “We don’t have a lot of data
yet,” he explains. “But obviously we
don’t implant the Flexivue in patients
with keratoconus or significant corneal
dystrophies. Also, significant astigmatism
is a contraindication because the
inlay doesn’t correct astigmatism. We
don’t believe the procedure will worsen
dry eye because we’re not making a
LASIK flap or ablating tissue.”
Nevertheless, Dr. Tamayo believes
that patient selection is critical. “In my
opinion, a monovision test conducted
with a +1.5 D contact lens in the
nondominant eye is crucial because
it gives the patient the opportunity to
experience the controlled monovision
the inlay produces,” he says. He adds
that the main limitation of the Flexivue
may be that monovision effect.
“Even though it’s very small, many
patients are sensitive to this approach.
The rate of rejection after the monovision
trial is almost 70 percent.”
Along those lines, some surgeons
have patients try bifocal contact lenses
before agreeing to implant an inlay,
but Dr. Maloney is skeptical about
the validity of this approach. “Bifocal
contact lenses work in a different way
than these inlays,” he notes. “The fact
that a patient likes the effect of bifocal
26 | Review of Ophthalmology | February 2014