Eyeworld

EW RETINA 114 September 2016 by Steve Charles, MD Vitrectomy without scleral buckling for rhegmatogenous retinal detachment Modern vitreoretinal surgical repair of retinal detachment without scleral buckling emulates the patient experience of today's refractive cataract surgery V itrectomy without scleral buckling for rhegmatoge- nous retinal detachment is often referred to as "pri- mary vitrectomy," a term that at least initially implied that scleral buckling was the standard of care and should be tried before resorting to vitrectomy. This "rescue therapy" approach is considered by some to be "conservative" and ap- plied in many specialties and disease processes, but can unintentionally delay adopting improved therapies and put the patient through an unnecessary procedure. Anterior segment surgeons do not try intra- capsular cataract extraction before resorting to phaco or RK before LASIK. Long bone fractures were not randomized to sham therapy after casts were developed. There are no high quality clinical trials compar- ing vitrectomy, scleral buckling, and combined vit-buckle procedures for rhegmatogenous retinal detachment surgery because there are a high number of clinical variables and many treatment options that are often used in combination. Preoperative variables include type, size, and number of breaks; lens status; refractive error; vitre- ous hemorrhage; vitreous traction; family history; status of the other eye; medical status; and others. Variables in scleral buckling in- clude hard silicone versus sponges, subretinal fluid drainage versus non-drainage, radial versus circum- ferential elements, encircling versus segmental buckles, use of air or gas, paracentesis, and many others. Variables in vitrectomy include air, SF 6 , C 3 F 8 or silicone oil, laser versus cryo, 20-, 23-, or 25-gauge, use of liquid perfluorocarbons, combined lensectomy or phacoemulsification, postoperative positioning, and many others. Scleral buckle advocates have stated that pneumatic retinopexy often causes PVR, but they manage "fish-mouthing" in scleral buckling with gas injection. This is not ratio- nal. Some surgeons use vitrectomy only for pseudophakic eyes thinking incorrectly that vitrectomy causes de novo nuclear sclerosis when, in fact, it only causes progression of pre-ex- isting nuclear sclerosis due to higher partial pressure of oxygen caused by a 900 X viscosity reduction. Complications of scleral buckling Proponents of scleral buckling often minimize its complications and state that they "never" produce strabis- mus. Yet a high quality prospective trial reported by Ron Michels and colleagues 1 demonstrated a 50% incidence of increased tropias and phorias. Encircling buckles may result in damage to the superior oblique or superior rectus tendons producing problematic vertical strabismus. Fortunately, most buckle surgeons have given up the unnec- essary practice of removing and reattaching extraocular muscles. Aggressive traction on retromuscle traction sutures especially with small diameter sutures can damage and potentially sever intraocular muscle tendons. Aggressive stripping of the intramuscular septum, Tenon's cap- sule, and episclera combined with cautery can create adhesions be- tween these layers, causing problems if subsequent glaucoma filtering procedures are required. Patients spend substantial sums of money in the pursuit of em- metropia; LASIK, PRK, and refractive lens exchange have raised patients' expectations of life without glass- es or contacts. Cataract surgery patients expect emmetropia as well; substantial effort has been applied to refractive microincisional surgery, foldable IOLs, toric IOLs, multifocal intraocular lenses, accommodative IOLs, intraoperative aberrometry, and femtosecond laser surgery. An encircling band produces 2.75 D of myopia on average; this is complete- ly unacceptable to a patient who has paid for refractive cataract surgery, LASIK, or PRK. More serious complications of scleral buckling include late in- trusion of the buckle and buckle extrusion and infection. Intraoper- ative complications include a 5% incidence of retinal incarceration at the drainage site when using cut- down drainage as well as bleeding related to the drainage site. Scleral, choroidal, retinal perforation with scleral sutures is not uncommon as well, sometimes with serious conse- quences. Vit-buckles Many vitreoretinal surgeons use en- circling bands in conjunction with vitrectomy for repair of rhegmatog- enous retinal detachment—so-called vit-buckles. I have not used this approach for two decades in order to eliminate buckling-induced refrac- tive errors, strabismus, ptosis, and pain as well as to reduce operating times and therefore labor costs. Brazitikos 2 has shown that vitrec- tomy without scleral buckling for retinal detachment produces better outcomes than vit-buckles. Patients would not want a vitreoretinal sur- geon to use encircling bands when having vitrectomy repair of retinal detachment if they were informed about outcomes and complications. There is no level I evidence that vit-buckles produce better outcomes than vitrectomy without scleral buckles, even in PVR cases. Vitrectomy techniques Wide-angle visualization techniques and/or scleral depression are essen- tial if vitrectomy is to be used for retinal detachment repair. Con- tact-based wide-angle visualization (Advanced Visual Instruments, New York; Volk Optical, Mentor, Ohio) produces 10 degrees of greater field of view than non-contact (BIOM, Oculus Surgical, Port St. Lucie, Flor- ida; RESIGHT, Carl Zeiss Meditec, Jena, Germany) and eliminates all corneal asphericity (keratoconus, LRI, RK, PK, cataract surgery, LASIK, PRK). In addition, contact-based wide-angle visualization greatly reduces the need for ocular rotation to view the periphery, which reduces flexural forces on 25- and 27-gauge tools. Just as with scleral buckling, all retinal breaks must be identified and treated with retinopexy. Trac- tion to the flap as well as vitreous traction surrounding all breaks must be eliminated to produce ~90% single procedure success rates for experienced surgeons. Internal drainage of subretinal fluid per- formed simultaneously with fluid-air exchange with a soft-tip cannula usually drains most of the subretinal fluid. Drainage retinotomy can be used if substantial posterior migra- tion of subretinal fluid occurs or the retinal breaks are very small and far peripheral, which can make internal drainage challenging. Another option for subretinal fluid removal is perfluorocarbon liq- uids; n-perfluorooctane (PFO) is the preferred agent because the interface is visible, unlike perfluorodecalin. PFO will remove all subretinal fluid if the optimal techniques are uti- lized, while internal drainage of sub- retinal fluid plus fluid-air exchange always leaves a thin layer of fluid that must be pumped out by the RPE. Complete removal of subretinal fluid enabled by PFO may allow use of a shorter acting gas or even air for surface tension management. Because PFO causes subretinal fluid to float anteriorly, care must be tak- en to remove all SRF anterior to the retinal breaks to enable surrounding all breaks with endolaser. This can be done by extending the break to the ora or making a very peripheral, small drainage retinotomy, but the best approach is to slowly drain SRF through the retinal break using a 25-gauge soft-tip cannula just when the PFO reaches the break. Care Retina consultation corner Steve Charles, MD

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