Improved Flap Nerve Apposition and Corneal Sensation

Improved Flap Nerve
Apposition and
Corneal Sensation
with iFS Technology
Case Study Series, No. 1
Eric D. Donnenfeld, MD,
noticed that he was getting
fewer complaints about dry eye
symptoms after he began using
the iFS Advanced Femtosecond
Laser from Abbott Medical
Optics Inc. “Dry eye can
sabotage high-quality vision
and patient satisfaction,” he
says. “In fact, it’s the most
common postoperative problem
after LASIK.” Dr. Donnenfeld
knew that finding a way to
reduce the impact of refractive
surgery on the ocular surface
would be a boon to patients
and to his practice, Ophthalmic
Consultants of Long Island.
The iFS Flap Advantage
Compared to a microkeratome, the
IntraLase Technology offers more
precise control of flap thickness,
diameter, hinge width and centration,
for minimal disruption of the cornea’s
biomechanical properties. “In recent
years, the ability to consistently make
thin flaps has been very beneficial,”
Dr. Donnenfeld says. Creating a
110-µm planar flap, for example, can
preserve the network of corneal nerves
located just below that, at a depth of
120-140 µm.
But the latest technology takes this one
step further. “One of the great advan­
tages of the iFS Laser is that surgeons
can customize so many more aspects
of the flap, including the shape, sidecut
angle, and hinge size and location.”
Treating dry eye aggressively before
and after surgery with artificial tears,
anti-inflammatory therapy and treat­
ment for meibomian gland dysfunction
is critical, according to Dr. Donnenfeld.
Flap dissection inevitably severs some
of the nerves that innervate the eye,
disrupting the normal cycle of corneal
sensation and tear production.1 “It’s a
basic neurosurgical premise that one
should optimize the apposition of the
two ends of the nerve,” Dr. Donnenfeld
says. A reverse sidecut, much like
tongue-and-groove architecture, cre­
ates a flap-stroma interface that aligns
the nerves in each portion of the tissue.
“That helps return corneal sensation
faster,” he says.
Faster Return of Corneal
Sensation
In a multi-center, randomized, observermasked study, Drs. Donnenfeld,
Solomon and Knorz compared flaps
with a 30° sidecut angle to flaps
with a 140° inverted bevel-in reverse
sidecut in 49 subjects undergoing
bilateral CustomVue LASIK2. All flaps
were created with the iFS Laser to be
110 µm thick, round, and 8.5 mm in
diameter, with 50° nasal hinges. Energy
levels were standardized for both types
of cuts. Ü
The inverted bevel-in side cut improves
severed nerve apposition.
“There are several key benefits to the iFS System. The most common problem
after laser surgery is dry eye and I have seen that by using reverse side cuts, you
actually have less post-operative dry eye symptoms.”
—Eric Donnenfeld, MD, TLC Laser Eye Centers, Garden City, NY
The iFS laser system is an ophthalmic surgical laser indicated for use in patients undergoing surgery or treatment requiring the initial
lamellar resection of the cornea.
Improved Flap Nerve Apposition and Corneal
Sensation with iFS Technology
One randomly selected eye of each
patient received a 30-degree side cut,
which is similar to the architecture of a
conventional microkeratome flap, while
the fellow eye received the 140° reverse
side cut.
The reverse sidecut produced sig­
nificantly less corneal and conjunctival
staining at 90 days (Figure 1). Patients
also had significantly better corneal
sensation and tear break-up time (TBUT) flap with reverse sidecuts produced
at 90 and 180 days (Figure 2 and 3).
better corneal sensation than round
flaps with 70° sidecuts at all time points
Elliptically-shaped flaps, possible only
in the three months after LASIK3.
with the iFS Laser, may further protect
against loss of corneal sensation. The
“There are many steps we can take
elliptical flap reduces the vertical dia­
to improve ocular surface health after
meter of the flap and widens the hinge, surgery,” says Dr. Donnenfeld. “Creating
and may preserve more of the vital
a flap that improves nerve apposition
peripheral lamellar fibers and nerves.
and preserves corneal sensation is a
In another recent study, Dr. Donnenfeld smart choice for our patients.” n
and colleagues showed that an elliptical
Lissamine Green Conjunctival Staining: Nasal
140° Side Cut
30° Side Cut
0.8
0.9
0.8
0.7
0.6
0.6 0.6
0.5
0.4
0
0.4
0.4
0.3
0.3
0.3
0.2
Baseline
30° Side Cut
5.7 5.8
5
Day 7
Day 30
Day 90
5.8
5.5
4.3
3
2.8
2
1.4
0
Day 180
P < .001
4
1
Day 1
P < .001
140° Side Cut
6
P < .001
Mean Score
Mean Score
1.0
0.2
Corneal Sensation: Central
Baseline
0.6 0.4
0.5 0.6
Day 1
Day 7
Figure 1
1.1
Day 30
Day 90
Day 180
Figure 2
TBUT
14
140° Side Cut
12
Mean Score
10
30° Side Cut
11.8 11.7
P < .023
9.2
8
7.7 7.4
6
8.3 8.1
8.5
Day 7
Day 30
8.5
9.1
P < .045
9.3
8.8
4
2
0
Baseline
Day 1
Day 90
Day 180
Figure 3
1. Donnenfeld ED, Solomon K, Perry HD, Doshi SJ, Ehrenhaus M, Solomon R, Biser S. The effect of hinge position on corneal sensation and dry eye after LASIK. Ophthalmology 110:1023-1029, 2003.
2. Barsam A, Donnenfeld ED, Solomon KD, Knorz MC. Evaluation of corneal sensation and signs and symptoms of dry eye in eyes receiving 30-degree side cut or 140-degree reverse sidecut in bilateral femtosecond flap
formation LASIK. American Society of Cataract and Refractive Surgery (ASCRS) Annual Symposium, March, 2011, San Diego, Calif.
3. Binder PS, Chayet AS, Donnenfeld ED. Impact of flap architecture on healing, visual quality, and acuity results. American Society of Cataract and Refractive Surgery (ASCRS) Annual Symposium, April, 2010, Boston, Mass.
The IntraLase FS and iFS Laser Systems are ophthalmic surgical lasers indicated for use in patients undergoing surgery or treatment requiring the initial lamellar resection of the cornea. Contraindications
may include cornea edema, glaucoma, and keratoconus. Risks and complications may include corneal pain, flap tearing, and epithelial ingrowth. Patients are requested to consult with their eye care
professional for a complete listing of the contraindications and risks. U.S. Federal Law restricts this device to sale, distribution, and use by or on the order of a physician or other licensed eye care professional.
©2011 Abbott Medical Optics Inc. IntraLase, CustomVue and iFS are trademarks owned by or licensed to Abbott Laboratories, its subsidiaries
or affiliates.
2011.09.30-RF4101