Download Improving Clear Corneal Wound Integrity

CATARACT SURGERY FEATURE STORY
Improving Clear Corneal
Wound Integrity
In situ-forming hydrogel bandages mimic living tissue.
BY DANIEL CALLADINE, MRCO PHTH , BMBS, BM ED S CI
H
ydrogels, which mimic living tissue more than
any other synthetic biomaterial because of their
high water content and tensile strength, have
numerous clinical applications in ophthalmology.
Their soft, rubbery consistency can minimize friction with
surrounding cells and tissue,1 and their degree of flexibility
is similar to the eye’s natural tissues. Polyethylene glycol
(PEG), the main component in many hydrogels, is commonly found in drugs, implants, and injectables. Use of
hydrogels also avoids the risks associated with medical
technologies based on biological components such as
human thrombin materials.
Currently, two ocular bandages made from PEG hydrogels
are commercially available in Europe: the ReSure Adherent
Ocular Bandage (Ocular Therapeutix, Inc., Bedford,
Massachusetts) and OcuSeal Liquid Ocular Bandage
(Roundtable Healthcare Partners, Lake Forest, Illinois).
I have used both products, but I prefer ReSure for the
following reasons:
• Its foam-tipped applicator enables accurate placement
over the incision;
• Up to four transfers of material can be obtained from
each mixture before it polymerizes, which is particularly
useful when applications are made at different stages of
the procedure; and
• A visualization aid (FD&C Blue No. 1) helps determine
thickness and placement of the application, especially on a
transparent surface such as the cornea. The dye thereafter
diffuses from the hydrogel and leaves behind a transparent
material within 1 or 2 hours.
The PEG component of the hydrogel is supplied as a
powder that, when mixed with a diluant, forms a blue precursor (Figure 1). I recommend mixing these components
approximately 5 minutes before the surgeon is ready to
use the hydrogel. First, a drop of the blue precursor and a
drop of an accelerator solution (buffered sodium phosphate tetraborate decahydrate) are placed on a hydrophobic foil pouch (Figure 2). Once the blue precursor and
accelerator are mixed, they react to form the hydrogel in
approximately 30 seconds.
Figure 1. The scrub nurse interlocks the PEG powder syringe
with the diluent syringe to create the blue precursor.
A
B
C
Figure 2. (A) A drop of blue precursor (top) and a drop of
accelerator solution (bottom) are placed on the foil packet.
(B) The surgeon uses the blunt end of the foam-tipped
applicator to mix the two components and activate
polymerization. (C) The foam-tipped end of the applicator is
used to transfer the hydrogel to the ocular surface.
APPLICATION TIPS
Tip No. 1: The ocular surface at the site of application
must be dry to achieve appropriate adhesion. If applied
to a wet surface, the hydrogel will migrate with the fluid
before it has time to polymerize over the wound. I have
found the best method for application is to place a cellulose spear or surgical sponge over the wound with one
hand until the hydrogel is applied with the other hand.
JULY/AUGUST 2011 CATARACT & REFRACTIVE SURGERY TODAY EUROPE 29
CATARACT SURGERY FEATURE STORY
OcuSeal Liquid Ocular Bandage
This device provides a barrier against microbial infection.
BY MATTEO PIOVELLA, MD
The clear corneal incision (CCI) is arguably the most pop- A
B
ular wound construction technique for modern cataract
surgery. Preferred for their self-sealing properties, CCIs avoid
induced astigmatism and excessive bleeding in the majority
of cases. I typically construct a CCI and use a liquid ocular
bandage for added protection.
Of the two hydrogel liquid ocular bandages commercially
available in Europe, I use OcuSeal (Beaver-Visitec International,
Ltd., Oxfordshire, United Kingdom; Figure 1) to ensure safe closure of CCIs after cataract surgery. Within 20 seconds of applyFigure 1. (A, B) OcuSeal packaging. The bandage is applied
ing OcuSeal to the ocular surface, the crosslinked liquid forms a directly on the surface of the eye to provide an immediate
smooth and transparent barrier to protect the corneal incision
protective barrier.
from microbial infection, allowing the incision to heal and possensation immediately after surgery. (This event was mainly
sibly providing added protection from endophthalmitis. The
due to the learning curve associated with the proper mixing
bandage, undetectable by slit-lamp evaluation just hours after
time.) However, in most cases the patient’s eye blinking is
application, lasts for 1 to 2 days. It degrades and disappears
enough to remove the excess within 12 hours after applicafrom the incision site within 4 days, coinciding with recovery of
tion. If too much OcuSeal is applied, it is possible to remove
the epithelium and formation of new tissue at the wound site.
the surplus immediately with a sponge and start again with
OcuSeal is supplied as two components, a powder polyetha new application.
ylene glycol and a liquid polyethylene amine. When mixed and
shaken for 5 seconds, they form the hydrogel bandage. This
CLINICAL EVALUATION
bandage can then be applied directly to the ocular surface.
We recently conducted a study of 123 eyes (91 patients) in
which the OcuSeal hydrogel liquid bandage was applied to
TIPS
the CCI of one or both eyes at the end of routine cataract surFor a video demonstration of the use of OcuSeal, visit
gery. The incision size was approximately 2.8 mm in most
http://eyetube.net/?v=nenik. There is a short learning curve
cases. When we implanted the Synchrony IOL (Abbott
associated with the use of OcuSeal. I noticed some difficulty
Medical Optics Inc., Santa Ana, California), we enlarged the
in applying the bandage quickly enough. Because OcuSeal
incision to 3.75 mm. There were no adverse events, and the
polymerizes in 15 seconds, it is imperative that application
sealed wound appeared to increase patient comfort, with only
occurs as soon after the two components are mixed as pos15% of patients reporting foreign-body sensation 1 day after
sible to avoid a surplus of OcuSeal on the wound.
surgery. However, in the 63 eyes that had unilateral applicaAnother hiccup can occur if too much OcuSeal is applied
tion, 70% reported foreign-body sensation in the eye without
to the ocular surface, which can result in mild foreign body
OcuSeal. These results are based on the fact that any corneal
WATCH IT NOW ON THE CATARACT SURGERY
incision creates some amount of damage to the epithelium.
CHANNEL AT WWW.EYETUBE.NET
Additionally, it appears that applying OcuSeal to the
wound blocks the CCI from letting infectious bacteria into
Using your smartphone, photograph
the eye, thus decreasing the risk for endophthalmitis.
the QR code to watch the video
on Eyetube. If you do not have a
QR reader on your phone, you can
download one at www.getscanlife.com.
direct link to video:
http://eyetube.net/?v=nenik
Matteo Piovella, MD, is Director of the Centro di
Microchirurgia Ambulatoriale, Monza, Italy. Dr.
Piovella states that he is a consultant to Abbott
Medical Optics, Inc., and Beaver-Visitec
International. He may be reached at tel: +39 039
389 498; e-mail: [email protected].
30 CATARACT & REFRACTIVE SURGERY TODAY EUROPE JULY/AUGUST 2011
Visit Angiotech Booth B822
during ESCRS
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C
Figure 3. (A) OCT of a CCI showing a microleak captured
underneath the hydrogel. (B) The same image, with the CCI
profile highlighted in green. (C) Photographs taken with the
OCT scanner show the location of the slice. The CCI is demarcated in green, and the leaking bleb of fluid at the external
lip of the wound (underneath the hydrogel) is shown in red.
Tip No. 2: Use only enough hydrogel to cover the incision. The hydrogel adheres to the ocular surface according
to how much epithelial damage surrounds the wound.
With more expansive epithelial damage, selective and prolonged adherence can last up to 2 weeks, thus eliminating
the need for multiple layers of hydrogel. Avoid applying
excess hydrogel, as too much material can create a protuberance and lead to foreign body sensation.
IMPROVING WOUND INTEGRITY
Wound integrity of clear corneal incisions (CCIs) can be
compromised in the first few hours after surgery by deforming forces such as removal of the lid speculum, sneezing, and
squeezing or rubbing the eye. Resulting changes in intraocular pressure (IOP) can lead to leakage and hypotony, which
can trigger further complications. Additionally, a suction
effect as the anterior chamber attempts to maintain a stable
IOP can result in ingress of fluid from the tear film—a
significant risk factor for endophthalmitis.
I recently tracked the wound architecture and healing
pattern of CCIs with (n=22) and without (n=23) the use of
the ReSure hydrogel bandage. Within 2 hours of surgery
To learn more about our complete line of Sharpoint™ disposable
products, including knives, sutures, cannulas and eye shields:
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Or use your favorite QR code scanning
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CATARACT SURGERY FEATURE STORY
TAKE-HOME MESSAGE
A
B
C
Figure 4. A sideport incision made with a 15º blade with
typical linear profile. (A) Immediately after surgery the
ReSure hydrogel covers the wound. (B) Day 1: Areas of
epithelial defect are plugged with ReSure hydrogel, giving a
smooth, in-line surface profile. (C) Day 7: The ReSure hydrogel
is replaced by healed epithelium.
A
B
C
D
Figure 5. Coaxial microincision cataract surgery case with
a 2.2-mm CCI with damage to the epithelium around the
wound. (A and B) Immediately after surgery: ReSure covers
the wound. (C) Day 7: Most of the ReSure has dissolved in
the presence of healing epithelial tissue. The hydrogel
remains plugged over the wound with a smooth surface
profile. (D) Day 14: The hydrogel is completely replaced by
epithelial tissue.
• Hydrogel bandages form a smooth in-line profile to cover
areas of epithelial damage.
• These bandages are a useful adjunct in cataract surgery,
especially when the wound architecture is questionable.
• Ocular bandages are gradually replaced by healing tissue
and are usually gone from the eye by 1 week after surgery.
and at 24 hours and 7 days after surgery, optical coherence
tomography (OCT) images were obtained. CCIs with the
hydrogel bandage had relatively higher IOP than CCIs in
the control group (19.4 ±5.94 mm Hg vs 13.4 ±5.28 mm
Hg; P<.001). Microleaks captured under the hydrogel at
the external lip of the wound could also be observed
(Figure 3). This finding suggests that microleaks, difficult to
detect with Seidel test but clearly visible as a bleb of fluid
beneath the hydrogel,2 may be more common than previously thought. Because they can lead to a decrease in IOP
following surgery, microleaks can cause internal endothelial wound gape and other wound complications.
CONCLUSION
Hydrogel bandages form a smooth in-line profile to
cover areas of epithelial damage with the appearance of
pseudoepithelium (Figures 4 and 5). They improve patient
comfort, particularly in the first few days following surgery,
and in the majority of eyes they are gone by 1 week after
surgery as they are gradually replaced by healing tissue.
The ReSure hydrogel bandage is a useful adjunct in
cataract surgery, especially if the quality of the wound
architecture is questionable, such as those created by a
junior surgeon in training or when the wound is too short
or steep. Higher-risk patients—those with diabetes, those
who have had previous vitreoretinal or glaucoma surgery,
and those in whom premium IOLs (toric or multifocal) are
being implanted, where the lens will require good stability
in the capsular bag—would also benefit from the added
protection of a hydrogel bandage. ■
Daniel Calladine, MRCOphth, BMBS, BMedSci, is
a Registrar Ophthalmologist in the Oxford Deanery,
United Kingdom. He is also a postgraduate research
student with Nottingham and Reading Universities,
investigating new applications for hydrogels in ophthalmology. Mr. Calladine states that he has no financial interests in the products or companies mentioned. He may be
reached at e-mail: [email protected].
1.Ratner BD,Hoffman AS.Synthetic hydrogels for biomedical applications.Hydrogels for Medical and Related Applications.
1976:31:1-36.
2.Calladine D,Ward M,Packard R.Adherent ocular bandage for clear corneal incisions used in cataract surgery. J Cataract
Refract Surg.2010;36:1839-1848.
32 CATARACT & REFRACTIVE SURGERY TODAY EUROPE JULY/AUGUST 2011