OSLI Retina

October 2019

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October 2019 ยท Vol. 50, No. 10 661 The Cutting Edge Edited by Yoshihiro Yonekawa, MD, and Peter H. Tang, MD, PhD Gene therapy offers a novel approach to treating inherited retinal dystrophies. In this video, Dr. Berrocal's group has showcased their excellent technique for treating RPE65-associated Leber congenital amaurosis using vo- retigene neparvovec-rzyl. One of the most challenging aspects of this surgery is induc- ing a posterior vitreous detach- ment in a young eye. Removing the cortical vitreous from the vicinity of the injection site is critical to avoid plugging the in- jection cannula and postopera- tive vitreous contraction over the treatment area. Intraocular triamcinolone can be used to highlight residual hyaloid that will need to be me- ticulously removed, as shown in the video. Although wide-angle non-contact viewing plat- forms for vitrectomy have significantly improved our speed and safety, I recommend a fundus contact lens during portions of the case involving the mac- ula, as the authors did. These lenses offer enhanced depth perception and greater resolution, which are key. Many surgeons prefer to trim the 38-gauge sub- retinal cannula into a beveled tip. I have successfully created large blebs using the standard cannula, and there have been preliminary reports suggesting a link between a beveled cannula with higher rates of cap- illary bleeding at the injection site. The authors were astute to lower the intraocular pressure to around 10 mm Hg prior to the injection, as this softens the eye and allows for an easier delivery of the vector vol- ume subretinally. Finally, the postoperative transient ocular hy- pertensive response experienced by this patient is likely due to the sub-Tenon's triamcinolone injec- tion performed at the end of surgery. To avoid this while still minimizing postoperative inflammation, I initally perform a retrobulbar injection of 40 mg of triamcinolone mixed with a 1:1 mixture of 2% li- docaine and 0.5% bupivacaine. The anesthetic pro- vides prolonged postoperative analgesia and helps stabilize the globe intraoperatively. Placement with- in the retrobulbar space prevents anterior migration of the steroid past the equator and may reduce ocular hypertensive side effects. As this therapy becomes more mainstream, it will hopefully lead to the development of further treat- ments for numerous inherited eye diseases. Albert M. Maguire, MD Scheie Eye Institute Philadelphia, PA Albert M. Maguire, MD Subretinal Injection of Voretigene Neparvovec-rzyl in a Patient With RPE65- Associated Leber's Congenital Amaurosis Rehan M. Hussain, MD; Kimberly D. Tran, MD; Audina M. Berrocal, MD ABSTRACT: Leber's congenital amaurosis (LCA) is a rare inherited retinal degeneration (IRD) that causes severe vision loss, nyctalopia, and nystagmus within the first few years of life. RPE65 gene mutations cause approximately 6% of LCA cases and have become the target for therapy since voretigene neparvovec-rzyl became the first U.S. Food and Drug Administration- approved gene therapy product for IRDs in 2017. The surgery involves pars plana vitrectomy with subretinal injection of a viral vector that carries a functional copy of the RPE65 gene. Intraoperative optical coherence tomography is a useful adjunctive tool to confirm the injection has reached the subretinal space. L eber's congenital amaurosis (LCA) is a severe form of autosomal recessively inherited retinal degeneration (IRD) with a prevalence of approximately 1:80,000 spread across 19 disease variants, each caused by a unique genetic mutation. 1 Biallelic mutations in the RPE65 gene account for approximately 6% of LCA cases and 2% of overall recessive early onset retinitis pigmentosa. 2,3 The gene

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