Surgeon: Investigational bandage may ease cataract wound coverage
Another surgeon recommended the use of algorithms when calculating IOL power post-LASIK.
A new hydrogel adherent ocular bandage not yet approved by the U.S. Food and Drug Administration has shown promise for clear-cornea sutureless cataract surgery wound coverage, reported John A. Hovanesian, MD, at the San Francisco Continuing Education Symposium.
ReSure Adherent Ocular Bandage (Ocular Therapeutix) is made of a polymer that is applied as liquid to the clear cornea incision site. The liquid polymerizes, becomes a gel and covers the wound in situ. In 3 to 5 days, the material liquefies and either biodegrades or sloughs off in the tears. The bandage is CE-mark approved and commercially available in select European markets and Australia, according to the manufacturer.
In the U.S. pilot study testing ReSures safety and efficacy, 20 patients were randomized to receive either ReSure or collagen shield at the conclusion of their clear-cornea cataract surgery, Dr. Hovanesian, a Primary Care Optometry News Editorial Board member, reported. ReSure persisted at the wound site between 24 hours and 3 days after surgery. Trace remains were seen at 7 days postop.
Incisional healing was excellent with no epithelial defect observed in study subjects. This material could provide a safe and effective method of keeping the corneal wounds covered after cataract surgery, Dr. Hovanesian said. The study enrollment has been completed and the data submitted to the FDA.
Biomaterials for pterygium surgery
Dr. Hovanesian also presented the latest data on tissue adhesives and new biomaterials used in modern pterygium surgery. While he emphasized the importance of covering the scleral excision site with tissue to avoid recurrence, he pointed out that the traditional method of suturing the conjunctival autograft to the site is time consuming. In addition, the sutures can be irritating and even painful to the patient.
To simplify the surgery and ease the recovery process, Dr. Hovanesian recommended tissue adhesive instead of sutures and an amniotic membrane graft instead of a conjunctival autograft.
Images: Hovanesian JA
The tissue adhesive, called fibrin glue, utilizes a reaction between fibrin and thrombin, which are placed on the scleral site and the graft, respectively. They are permitted to react with each other, adhering the graft to the sclera. The fibrin and the thrombin are derived from human plasma and are the components of a blood clot an essential step in the wound healing process that adheres the sides of the wound to each other.
Fibrin glue is commercially available, Dr. Hovanesian said. It can be easily purchased and used not only in pterygium surgery, but also in other anterior surface procedures, such as closing the flap edge after epithelial ingrowth removal to prevent recurrence, for example. (A pterygium surgery instructional video is available at www.osnsupersite.com/view.aspx?rid=65337.)
The accompanying chart demonstrates lower postoperative pain index in patients who underwent pterygium excision with tissue adhesive vs. sutures.
In addition to tissue adhesives, Dr. Hovanesian described the use of biomaterials that can be used in place of the graft itself. These materials are derived from human amniotic membrane and are carefully processed to be readily available for order, storage and easy surgical handling. The amniotic membrane sheets have the additional benefit of working well with the tissue adhesives, he said.
Calculating IOL power post-LASIK
Victor Chin, MD, director of Cataract and Lens Surgery at Pacific Vision Institute, presented a case series demonstrating the most advanced techniques for calculating IOL power in patients with a history of corneal refractive surgery who are undergoing cataract and refractive lens exchange procedures
Dr. Chin discussed how the change in relative curvature between the anterior and posterior corneal surface as a result of myopic LASIK will often be misinterpreted by ophthalmic diagnostic equipment to suggest artificially high corneal power. He showed that using these measurements to calculate the proper IOL power may lead to unexpected hyperopic results.
Dr. Chin reviewed how specialized formulas, taking into account the new corneal shape and the type of refractive correction performed are required for accurate IOL power calculation. He said the new advanced algorithms that compensate for these corneal changes are required to prevent refractive surprises.
LASIK treatments for hyperopia will also affect keratometry measurements, he added. However, because the ablation area is more paracentral, the central cornea may be less affected, and power measurements are more reliable. Nevertheless, advanced algorithms are still required to produce reliable refractive outcomes after IOL implantation in these patients, he said.
Dr. Chin also discussed strategies for accurate IOL power calculation after radial keratotomy. He emphasized that RK affects the anterior and posterior cornea equally and, consequently, the keratometry readings are less affected than post-LASIK. Analysis of the central cornea generally yields accurate corneal power measurements, he said.
Corneal refractive surgery can often introduce optical aberrations, Dr. Chin added, so aspheric intraocular lens technology should be emphasized as well, to maximize patients satisfaction.
Dr. Chin emphasized that cataract- and lens-based surgery in patients with a history of previous corneal refractive surgery are best performed in an environment with a convenient and seamless transition to LASIK or photorefractive keratectomy enhancement procedures to ensure that the desired refractive outcome is ultimately achieved. by Jennifer Le Coq
- Victor Chin, MD, is director of Cataract and Lens Surgery at Pacific Vision Institute. He can be reached at 1 Daniel Burnham Court, San Francisco, CA 94109; (415) 922-9500; firstname.lastname@example.org.
- John Hovanesian, MD, is a PCON Editorial Board member. He can be reached at 24401 Calle De La Louisa, Suite 300, Laguna Hills, CA 92653; (949) 951-2020; email@example.com.
- Disclosures: Dr. Chin has no direct financial interest in any of the products mentioned in this article nor is he a paid consultant for any companies mentioned. Dr. Hovanesian is a member of the scientific advisory board to Ocular Therapeutix and a consultant to IOP Inc., a commercial provider of human amniotic membrane for eye surgery.