A Fresh Look at Retinectomy and Subretinal Surgery
The appropriate use of two advanced surgical techniques.
Steve Charles, MD, FACS, FICS
|Steve Charles, MD, FACS, FICS, is clinical professor of ophthalmology at the University of Tennessee College of Medicine in Memphis. Dr. Charles reports significant financial interest in Alcon. He can be reached via e-mail at email@example.com.|
Robert Machemer, MD, introduced relaxing retinotomy primarily to address the structural issue of retina stiffened and fore-shortened by epiretinal membranes not removable without making an excessive number of retinal breaks using membrane peeling, scissors delamination, or segmentation. Simultaneously and independently, I introduced the technique of retinectomy; the difference between the two methods is that relaxing retinotomy results in substantial residual tissue anterior to the circumferential cut in the retina, while retinectomy removes all tissue anterior to the cut.
I believe retinectomy results in significantly less chronic hypotony, cyclitic membrane formation, and recurrent PVR than relaxing retinotomy. Case complexity issues, as well as the broad array of surgical variables, do not permit rigorous statistical proof of my conclusion.
Retinectomy can be used for severe, peripheral PVR and for retinal detachment secondary to trauma with fibrous scarring or retinal incarceration in scleral laceration sites. Similarly, retinectomy can be used for retinal incarceration in a subretinal fluid drainage site caused when using cut-down drainage during scleral buckling surgery. Retinectomy is occasionally required for advanced diabetic tractional retinal detachment cases, especially in the context of thin atrophic retina and highly adherent epiretinal membrane.
Some surgeons spend hours dissecting peripheral PVR, which creates more trauma and inflammation than retinectomy, as well as increasing anesthesia complications and dramatically driving up labor costs. There is no evidence that this strategy improves PVR outcomes, although it is widely practiced.
Many surgeons combine vitrectomy with scleral buckling in severe PVR cases, a practice I gave up 20 years ago. I have discussed the disadvantages of vit-buckles in a previous column. Retinectomy is preferable to using a scleral buckle for severe peripheral PVR. I often reoperate PVR cases referred by vitreoretinal surgeons who have used a vit-buckle approach; stiff retina is often in contact with the apex of the buckle, but the retina is unable to conform to the RPE posterior to the buckle. Retinectomy is ideal for these cases when combined with endolaser and medium-term perfluoro-n-octane or silicone oil. Buckles simply do not address the problem of foreshortened retina very well.
It is not necessary to use diathermy to treat the entire extent of the retinal cut; this approach increases proliferation. Large vessels can be pretreated with diathermy to prevent bleeding, but I usually perform combined retinopexy and hemostasis with 532-nm endolaser after retinectomy and reattachment using fluid-air exchange and internal drainage of subretinal fluid. As I described in my column on interface vitrectomy, retinectomy works very well under silicone oil.
Many surgeons use liquid perfluorocarbon (PFCL) for PVR cases and perform retinotomy or retinectomy with this high-specific gravity, low-viscosity material in place. This approach not infrequently results in subretinal, and especially subfoveal, PFCL. Intraoperatively, PFCL is indispensable for the management of giant breaks but unnecessary, in my opinion, in PVR cases.
Retina incarcerated in traumatic scleral wounds or subretinal fluid drainage sites can be severed from the attachment site before fluid-air exchange “under” infusion fluid. I usually perform what I call “incremental retinectomy” simultaneously with fluid-air exchange and internal drainage of subretinal fluid with the vitreous cutter. I refer to this strategy as the “reattachment experiment”; if subretinal air appears during this process, it indicates unrelieved traction. If vitreoretinal traction is identified, it easily can be removed “under” air (Figure 1).
Figure 1. If subretinal air persists, incremental retinectomy should be used.
Epiretinal membrane hidden by retinal folds may become visible at this point, as the folds subside and the ERM is put on the stretch. Forceps membrane peeling with the Alcon 25-gauge end-grasping DSP ILM forceps is used for inside-out membrane peeling under air. Membrane scrapers, picks, and forceps designed to get under the ERM are not used; end-grasping forceps membrane peeling always keeps ERM between the tool and the retina.
At this point, subretinal bands may become apparent; the technique for managing subretinal proliferation will be discussed in the next section. If the retina remains stiff after removal of all apparent vitreoretinal traction, ERM, and subretinal proliferation, this indicates the need for incremental retinectomy under air (or oil). The term “incremental” was used to emphasize that retinectomy, along with removal of any remaining vitreous, subretinal fluid, and ERM, is extended circumferentially until the retina becomes attached. If the retinectomy extends for 270º it is better to perform a 360º retinectomy because PVR will almost always cause the remaining 90º to contract.
Confluent laser (not spots) should then be performed along the edge of the retinectomy and extended to the ora at the ends. If the eye is inflamed, or epi- or subretinal blood is present, forego retinopexy, and use silicone oil for rhegmatogenous confinement. Laser can be performed weeks later when inflammation has subsidized and/or blood has been absorbed. Retinopexy on “hot” eyes is a major cause of PVR.
Interestingly, Dr. Machemer and I also independently and simultaneously developed subretinal surgery. The method I developed differs from those of other surgeons; I use what I call “punch-through retinotomy” to access subretinal bands (a.k.a. strands or dendrites), unless they can be removed through a pre-existing retinal break (Figure 2).
Figure 2. Punch-through retinotomy.
The Alcon 25-gauge end-grasping (not ILM) forceps are placed against the retinal surface over the sub retinal band at the point of highest elevation. The closed forceps are push ed through the retina, withdrawn slightly, opened, and advanced until one blade is on each side of the band. The band is then removed with a combination of tangential and perpendicular traction, using the blunt tip of the endoilluminator to hold the retina back.
At times, the band is so long that the endoilluminator must be used as a pulley to double the pull length and redirect the force along the retina. Care must be taken to observe the macula during removal to be certain that the band is not adherent to the posterior macular surface. It is possible to avulse the macula from the back if care is not taken.
Fibrovascular bands usually occur after trauma, at trans-scleral subretinal fluid drainage sites from a previous buckle, or if excessive retinopexy had been used on previous procedures. It is better to resect fibrous bands than to apply high force to remove them; excessive traction may result in severe choroidal bleeding or avulsion of the RPE and choroid.
Resection can be done with Alcon 25-gauge curved DSP scissors inserted using punch-through retinotomy. It is never necessary or advisable to initiate the retinotomy with diathermy, construct the retinotomy with the vitreous cutter, or make a retinal flap to access the subretinal space.
Subretinal bands and placoid proliferation are much less likely to recur than ERM; they should only be removed if they are causing retinal elevation, which is often not detected until the reattachment experiment described above is undertaken.
The methods described in this column are not required often, but are essential at times. The specific techniques I described have been effective for our fellows, as well as highly experienced colleagues of mine. I hope the readers find these techniques useful, and I invite reader feedback. RP