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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 A The Surgeon’s Edge B Disposable Ophthalmic Products 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: visit t t www.Sharpoint.com Or use your favorite QR code scanning program on your mobile device call t t 1 877 991-1110 (USA and Canada only) +001 732 626-6466 (International) email t [email protected] OPG-PM-406 6/11 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