Ординатура / Офтальмология / Английские материалы / Retinal and Vitreoretinal Diseases and Surgery_Boyd, Cortez, Sabates_2010

Figure 3: Diffuse Contraction. (a) Diathermy completely encircle the area of proliferation with extension to the surrounding normal retina or to the ora serrata.

(b) Large retinectomy surrounded with laser for 360o or to the ora serrata. Contracted retina removed with excision. The edges of retinal defect treated with diathermy, carrying out to the pars plana if retinectomy approaches the vitreous base.

anterior retina is usually treated using laser photocoagulation, cryoablation, or extension of the retinectomy to the ora serrata. When the retinectomy extends to the ora serrata, endolaser or transcleral cryotherapy should be applied across the ora serrata onto the pars plana to avoid accumulation of subretinal

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fluid with contraction of the vitreous base. Long acting gas or silicone oil is used for tamponade.

3. Circumferential Contraction (Figure 4)

Significant contraction of membranes at the vitreous base may lead to extensive circumferential contraction. Because the direction of the contraction is anterior-posterior, the posterior hyaloid pulls the retina centrally into a funnel shape. The circumferential contraction is difficult to relieve even with posterior hyaloid excision and membrane dissection, leaving the retina in a contracted state.

A broad encircling scleral buckle is used first, to minimize the contraction. Vigorous and compulsive epiretinal membrane dissection is performed to relieve the residual traction. This may best be achieved with the help of intraoperative intravitreal injections of triamcinolone, indocyanine green, or trypan blue.14-17 If the contraction is still persistent, then the vitreous is trimmed to the retinal surface, starting at the posterior hyaloid and advancing to the vitreous base. The hyaloid is often adherent to the membrane posterior to the vitreous base. The vitreous base should be shaved down to the retina, facilitated by scleral depression and/or with the use of a wide-angle viewing system.

A retinectomy is indicated when the retinal contraction is not adequately relieved by the above measures. PFCL is injected over the disc and filled toward the level of the residual contraction. The tamponade force of PFCL identifies areas of persistent retinal traction that must be released and stabilizes the

Figure 4: Circumferential Contraction. (a) Circumferential contraction of posterior vitreous base with radial folds. Retina is pulled into funnel configuration. (b) After vitrectomy, membrane peel and scleral buckle, circumferential retinotomy is performed under perfluorocarbon liquid (PFCL) and retina flattens.

retina during retinectomy or further membrane peeling. The height of the scleral buckle can be adjusted at this time to diminish any residual traction. A retinectomy is performed circumferentially and posteriorly into the normal retina. It is important to excise well into the normal retina to ensure proper attachment of the retina once the air or gas

is absorbed. Anteriorly, the retina is excised to the anterior-most level of traction.

4. Anterior Retinal Displacement (Figure 5)

After vitreous manipulation such as pars plana vitrectomy, trauma or pneumatic retinopexy, fibrous proliferation and contractions may occur at the vitreous base and lead to anterior retinal displacement. Pulling of the peripheral retina anteriorly toward the pars plana can lead to retinal detachment. Hypotony often results from fibrous proliferation and contraction over the ciliary body causing a ciliary body detachment.

Pars plana lensectomy is usually required to ensure adequate dissection of the anterior membrane. It is important to remove all lens material including the entire capsule to limit future contraction of the capsular bag.18 To eliminate the traction that displaced the retina anteriorly, an encircling scleral buckle is used to support the vitreous base. After peripheral vitreous and vitreous base shaving, a limited dissection of the anterior membrane is performed using external indentation and a bimanual internal technique with an illuminated pick or forceps and scissors.

If part of the anterior traction still persists despite the dissection and the scleral buckle, a peripheral retinectomy may be performed in order to relax the retinal traction and facilitate apposition to the underlying RPE. The retinectomy should extend into the normal peripheral retina to avoid any residual proliferative tissue.

Endoillumination may not be adequate in the extremely anteriorly displaced membranes.

Figure 5: Anterior Retinal Displacement. (a) Diathermy is applied to the area of retinectomy. (b) Anterior retinal displacement is released by removing membrane with scissors. (c) The 360o relaxing retinectomy is completed and photocoagulation applied.

The coaxial light of the operating microscope or external illumination may be the better solution. The use of a panoramic viewing system can greatly improve visualization and facilitate dissection of the peripheral retina.14

5. Giant Retinal Tear (GRT) (Figure 6)

A giant retinal tear is often accompanied by the inward curling of the anterior retinal edge. The intrinsic elasticity of the retina initiates the curling process, with migration of the RPE cells over the edge to the internal limiting membrane facilitating proliferation and contraction which results in PVR. The direction of traction can be anteroposterior or circumferential. If the retinal traction

(PFCL) is injected over the posterior pole, to the level of the anterior edge of the giant tear, to unfold the flap of the giant retinal tear. (c) Photocoagulation applied to the edges of the giant retinal tear following retinectomy of contracted elements not responsive to careful membrane dissection.

cannot be relieved by scleral buckling and membrane dissection, a retinectomy is needed to facilitate apposition of the retina to the underlying RPE.

Perfluorocarbon liquid is injected over the posterior pole, displacing subretinal fluid anteriorly to uncurl the flap of the retinal tear. Diathermy is then applied to the edges of the giant tear with extension to the normal surrounding retina. The entire proliferated retinal edge is excised to relieve traction. Care is taken not to leave any jagged area behind

to minimize future contraction. With PFCL stabilizing the retina, endophotocoagulation is applied to the entire area of GRT. During the initial phase of the fluid-air exchange, the anterior edge of the GRT is dried by suction with a soft-tipped needle beneath the anterior edge of the retina. Care is taken to ensure proper attachment of the retina in the area of the GRT. The fluid-air exchange is then completed to remove residual PFCL.

6. Subretinal Membranes

The approach to subretinal membranes is based on the location and extent of the membranes. The retinotomy should be made as peripheral as possible. An isolated band that exerts traction or causes tenting of the retina is best reached with a retinotomy adjacent to the membrane, preferably towards the middle of the band. Diathermy is applied to the retina at the selected location, and the diathermy tip can be used to enlarge the full thickness retinotomy. The retinotomy can be further extended if needed with scissors. The membrane is carefully grabbed with intraocular forceps and gently tugged to see if it will come loose. If the membrane can be gently pulled free, the membrane is pulled, regrasped, and then the remainder of the band snaked through the retinotomy and removed. The retinotomy should then be walled off with endolaser.

Care should be taken to avoid choroidal hemorrhage with aggressive pulling on the membrane if it is attached to the RPE/choroid. If the membrane will not easily come out, the membrane should be cut with scissors. This technique relaxes the membrane and reduces traction. If sections of the band are more accessible after sectioning, it should

be removed. Choosing to access the band towards its midline has two advantages: (1) long subretinal bands are removed efficiently;

(2) if the band is cut with scissors, there is now equal access to two ends of the band. If left behind, traction is likely to be equally relieved.

In the case of a subretinal sheet or napkin ring, a more extensive circumferential retinectomy is required. Endodiathermy is used to mark the location and cauterize blood vessels. Vitrector or scissors can be used to cut along the marked edges of the diathermy. The retina should be folded back on itself to expose the membranes on the undersurface of the retina and the RPE. In conjunction with perfluorocarbon liquids to stabilize the retina, careful dissection is used with bimanual techniques.

PROLIFERATIVE

VASCULAR RETINOPATHY / PROLIFERATIVE DIABETIC RETINOPATHY

Although rare, tractional retinal detachment associated with diabetic retinopathy may require retinotomy or retinectomy to relieve traction and facilitate reattachment. In the presence of fibrous proliferation, it is important to relieve all traction when retinal breaks are present. When the tractional retinal detachment extends to the macula area with reduced central visual acuity, an attempt is made to relieve retinal traction and restore macular anatomic integrity.

Due to long-standing ischemia associated with diabetic retinopathy, areas of the retina can become thin and atrophic. Care

should be taken to minimize retinal tearing during surgical manipulation. Diabetic membranes can be segmented or delaminated in most cases to relieve traction. However, when the fibrous contraction from the membrane is associated with a posterior break, a retinectomy surrounding the area of traction may have to be performed to relieve residual traction and promote reattachment.

1. Long-standing Fibrovascular

Proliferation

The same principles discussed for PVR apply here. Membrane dissection and scleral buckling are performed first to relieve traction. If traction still persists, a retinectomy is then performed. Diathermy is applied to the membrane and the surrounding retina. Care is taken to minimize the area of retina that needs to be excised. The retinectomy is performed either with a vitrectomy instrument or with scissors, which allows better control and precision. After ensuring the retinal traction is relieved, the edges of the retinal defect are treated with endophotocoagulation and a long-acting gas or silicone oil is used for tamponade.

2. Anterior Hyaloidal Fibrovascular

Proliferation (AHFVP)

Similar in clinical appearance to anterior retinal displacement, anterior hyaloidal fibrovascular proliferation (AHFVP) is caused by neovascular proliferation and contraction of the peripheral retina and extends to the anteriorhyaloidandalongtheposteriorsurface of the lens.19,20 With time, the contraction of the fibrovascular tissue pulls the peripheral retina forward leading to retinal detachment.

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AHFVP is usually seen in patients with severe proliferative diabetic retinopathy after vitrectomy. It differs from anterior retinal displacement by its prominent vascularity and propensity to bleed.

After a pars plana vitrectomy and lensectomy, a bimanual technique is used to dissect the membrane. Scleral depression of the peripheral fibrous tissue will facilitate visualization and dissection. Because of the high degree of vascularity, diathermy is applied to the vessels to achieve hemostasis before dissection. A two-function (illumination/coagulation) or three-function (illumination/coagulation/suction) instrument will provide readily available diathermy in the event of bleeding. Thrombin may be infused if significant bleeding occurs.21

Aretinectomy may be indicated if the retina fails to relax despite of careful membrane dissection. Depending on the extent of the contraction, the retinectomy may extend to encircle the peripheral retina. Endophotocoagulation is then applied to the edges of the retinectomy to ensure adequate attachment. Silicone oil is usually used to tamponade the retina and reduce the risk of anterior segment ischemia.

RETINAL

INCARCERATION

(Figures 7 and 8)

Retinal foreshortening and contraction can occur after open globe injury or inadvertent surgical incarceration. In addition to true retinal shortening due to tissue fixing to the wound site, fibrous proliferation during healing phase may exacerbate contraction. The severity of retinal shortening is dependent

on the size, location and chronicity of the wound. A retinectomy is usually indicated to relieve traction and facilitate reattachment of the retina.

After a standard three port pars plana vitrectomy, the wound is explored for its size, location and signs of chronicity such as the presence of retinal folds. Every attempt should be made to avoid inadvertent entrance into the subretinal space with the vitrectomy instrument, especially during traumatic repair when reduced visualization is a common occurrence.

If the wound is recent and no fixing of the retinal tissue to the wound is detected, the focus of incarcerated retina can be carefully teased out of the wound. Perfluorocarbon liquids (PFCL) may be used to facilitate the process.

In most traumatic cases, however, incarcerated retina must be excised because the retina cannot be dislodged from the wound site. After diathermy is applied carefully to encircle the area of incarceration, a scissors blade or a membrane pick is used to enter the subretinal space tangentially through the necrotic retina. The retina is carefully lifted away from the RPE before cutting. Repeated diathermy may be needed while cutting the retina in an annular fashion until the necrotic retina has been excised 360o around the wound site. PFCL, injecting over the posterior pole, may facilitate the attachment of the retina around the wound site. The edges of the retinal defects should be treated with endolaser and the eye filled with a long-acting gas or silicone oil.

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Complications

Hemorrhage is one of the major complications of retinotomy. Non-resolving intraoperative and postoperative hemorrhage can lead to fibrin formation and fibrous proliferation impairing final surgical outcome. To achieve complete hemostasis, meticulous application of diathermy is of significant importance. A continuous row of diathermy to the surrounding vessels is usually obtained before cutting, to minimize future oozing. However, care is taken to avoid excessive diathermy, which could lead to tissue necrosis.

In the event of hemorrhage during a retinectomy, infusion pressure should be raised, increasing intraocular pressure. In addition, use of a combination diathermy and a fiberoptic light source or a three-function tissue manipulator provides ready access to diathermy. Thrombin can be infused in the vitreous cavity in case of significant persisting hemorrhage.21

The incidence of hypotony (intraocular pressure less than 5 mmHg) is reported to be as high as 43% by Morse et al.22 It is more commonly seen after large retinotomies. Possible mechanisms include anterior fibrous proliferation leading to detachment of the ciliary body and less likely, increased absorption of intraocular fluid from the largely exposed RPE.

Retained subretinal or preretinal perfluorocarbon liquid may lead to retinal toxicity and contribute to poorer visual acuity if subfoveal.23 Retained subretinal perfluorocarbon liquid bubbles most frequently occur in cases of large peripheral retinotomies/

retinectomies. The incidence has been associated with retinotomies greater than 120 degrees and reported to be as high as 40% in eyes with a 360-degree retinotomy.24 Posterior small retinotomies usually do not increase the risk of subretinal PFCL.

Recurrent retinal detachment due to failure to relieve traction may occur if the retinectomy is too small and membrane dissection is incomplete, leaving fibrous proliferative tissue behind. To avoid such occurrence, retinectomy should be extended well into the normal retina in all directions to relieve traction. In addition, meticulous bimanual membrane dissection is imperative in complete removal of residual fibrous proliferative tissue.

Surgical Results

In 1986, Machemer et al reported the results of relaxing retinotomies in 56 eyes

of the eyes.

In 1990, Morse et al reported 100 eyes undergoing relaxing retinotomies in a retrospective series.18 At 6 months follow-up, 58 eyes were completely attached and 8 eyes had partial reattachment with the macula on. At the final follow-up, 29 eyes achieved visual acuity of 5/200, 17 eyes had 20/200 or better vision, and 5 eyes achieved better than 20/100 vision. The length of the retinotomy did not appear to affect the surgical outcome in the study. A radial relaxing retinotomy or a relaxing retinotomy involving the entire

temporal quadrant was, however, associated with poorer visual outcomes.

Similar results were reported by a case series by Han et al.25 Relaxing retinotomies were performed on 54 consecutive eyes (42 eyes for PVR and 12 for trauma) with a minimum follow-up of 6 months. 35 eyes (64%) achieved anatomic success (retina remained attached posterior to the scleral buckle with an intraocular pressure of 3mmHg or more). Visual acuity of 5/200 or better was achieved in 14 eyes (26%). Superior location of the relaxing retinotomy and preoperative visual acuity of hand motion or better are associated with better visual outcomes.

The Silicone Study, a multicenter, randomized, prospective clinical trial, evaluated the use of silicone oil and long-acting gas in eyes with severe PVR and helped to define the expected outcome for vitrectomy in these eyes.26 Onehundredseventeeneyeswithsevere proliferative vitreoretinopathy were treated with vitrectomy, underwent a relaxing retinotomy, and received either perfluoropropane gas (C3F8) or silicone oil. 46 eyes (20%) had no previous vitrectomy (group 1); 71 eyes (42%) had undergone previous vitrectomy (group 2). At the end of 6 months, 58% had anatomical attachment, 38% achieved visual acuity of 5/200 or better, 31% were hypotonic and 35% had corneal opacities.

A more recent report demonstrated high anatomical success and low rates of hypotony using combined circumferential retinectomies with radial relaxing retinotomy. Twenty-seven of thirty eyes (90%) with advanced PVR and circumferential foreshortening achieved retinal flattening with 6 months follow up without support from a scleral buckle. Median visual acuity was counting fingers. 27

Quiram et al28 report the results of inferior retinectomy for PVR and factors that may be associated with better anatomical success. Ninety-three percent of patients were anatomically attached by most recent follow up (mean 25 months) including 40% requiring additional retinectomy surgeries. Five of their patients underwent 3 or 4 retinectomy surgeries. In 70% of their patients, visual acuity remained stable or improved. They report that radical 360-degree anterior vitreous base dissection combined with lens removal had better surgical anatomical outcomes. Twenty-six of 35 (74%) patients who underwent 360-degree anterior vitreous base dissection with lens removal remained attached compared to 8 of 21 (38%) (p = 0.011) patients that did not.

Conclusion

Relaxing retinotomies and retinectomies are procedures to consider when other less aggressive measures fail in attempts to treat complex retinal detachments. Previously associated with dismal anatomical and visual results, the advancement of surgical methods and adjuncts have shown significant improvement in anatomical and functional success of retinal detachments associated with severe PVR and contraction.29

Scleral buckle and aggressive membrane dissection should be performed first to relieve retinal traction and minimize fibrous proliferative tissue. In eyes with severe PVR, proliferative vascular retinopathy or retinal incarceration, retinotomies and retinectomies are often needed to further relieve the traction and facilitate reattachment. Aggressive

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anterior vitreous base dissection combined with lens removal may increase re-attachment rates.

Relaxing retinotomies are most commonly performed circumferentially rather than radially. With the assistance of intraoperative PFCL, endocoagulation and long-acting gas or silicone oil tamponade, retinectomies have achieved better surgical success rate over the last decade. Using better techniques, instruments and adjuvants, the eyes that were once considered irreparable now have an opportunity for useful ambulatory vision.

Acknowledgments

Supported in part by the National Institutes of Health P30 EY06360 Departmental Core Grant and Research to Prevent Blindness, Inc.

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