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Fig. 10.22 The membrane has been removed from this macula
Fig. 10.23 See previous Þgure
10.2Surgery
Additional surgical steps
Stain the ERM with trypan blue. Peel off the ERM.
In cellophane maculopathy, vitreomacular traction or macular pucker, pars plana vitrectomy is employed to access epiretinal membranes, allowing their surgical dissection and removal. This is often effective in reducing distortion and
Table 10.1 DifÞculty rating for PPV for macular pucker
DifÞculty rating |
Easy |
Success rates |
Moderate |
Complication rates |
Low |
When to use in training |
Early |
ERM |
Pegs |
Retina
Fig. 10.24 ERMs have pegs of attachment to the retina
improving vision and is one of the easier procedures in vitreoretinal surgery (Michels 1981). In 20-gauge surgery, take a microvitreoretinal (MVR) blade and bend the end to about 45¡. Make sure the tip is secure. Some MVRs are made of a material that is brittle and snaps on bending. If so, use an intraocular pick. The 45¡ angle allows visualisation of the end of the MVR (it is difÞcult to judge the depth of the end of a straight blade or forceps, and, therefore, the likelihood of injuring the retina is increased).
Note: When approaching the retina with an instrument, watch the shadow of the instrument on the retina. When the shadow and the instrument tip join, you are on the surface of the retina.
Use the MVR to elevate an edge of the epiretinal membrane to allow the membrane to be grasped with some Þne forceps. In small-gauge surgery, use the forceps to grasp the ERM without Þrst lifting with the MVR blade; in this circumstance, it helps to grasp an edge if available to get started. Pull the membrane off the retina, trying not to tear the membrane whilst observing the retina to avoid damage from the traction. Usually by adjusting the angle of the traction, the membrane can be removed as one sheet. If there is a particularly strong attachment to the retina, do not pull away from the site of attachment; instead pull the membrane from around the attachment 360¼ and then over the top of it. The membrane is often much more extensive than expected sometimes, spreading beyond the arcades. Vitreomacular traction is a variant of epiretinal membrane and can be dealt with in a similar fashion.
The main aim is to relieve traction on the fovea. Do not leave membrane near to the fovea, that is, clear at least two disc diameters around the fovea. You may however safely leave membrane from the arcades outwards.
Occasionally, a PVD is not present and must be induced. Sometimes, the ERM will come with the vitreous but always check the retina with stain as there may still be ERM on the retina.
DifÞcult membranes can be stained with Trypan blue to aid visualisation or to conÞrm complete removal (Haritoglou et al. 2004a, b; Li et al. 2003; Stalmans et al. 2003; Teba et al. 2003). Indocyanine green has been used as an adjunct but has been associated with poorer visual acuity results and is best avoided (Haritoglou et al. 2003).
Pucker can be removed at the time of silicone oil removal in cases of PVR; often an ERM is more adherent to the retina in this pathology than in idiopathic ERM (Korobelnik et al. 1998)
10.2 Surgery |
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A
B A
Fig. 10.25 Use a bent MVR blade to lift the ERM to provide an edge. Scraping the ERM as per ILM peel does not create a hole or edge in the ERM because the ERM is elastic and will stretch with the movement of the blade; however, there is usually a virtual space between the ERM and the underlying ILM which can allow passage of a blade to commence lifting. Arrow shows direction of lift
Fig. 10.28 When you encounter a membrane with a particularly adherent point of attachment, work around this point of attachment (arrows A) to loosen the membrane all around it before trying to dissect the membrane off the point of attachment (arrow B). If it is particularly adherent, the membrane should either be segmented or the attachment cut
Retina
Fig. 10.26 By peeling the membrane back upon itself, most of the force is applied to the small pegs of attachment of the membrane rather than providing traction onto the retina itself
ERM
Retina
Fig. 10.27 By peeling the membrane upwards, there is a force applied to the edge of the retina, which should be avoided
Fig. 10.29 Trypan blue can be used to stain the ERM or as a weak stain of the ILM. Aim the dye away from the macula and allow the dye to fall back onto the macula. This avoids the risk of injection of dye under the retina if there is a sudden burst of dye during the commencement of the injection
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10.3Success Rates
Vision can be improved in 80Ð86 % (Haritoglou et al. 2003; Trese et al. 1983a) and to 20/60 or better in 75 %. Those with shorter duration, better presenting vision, thinner membranes and no retinal elevation do better (de Bustros et al. 1988b). Even if vision does not improve quality of life, scores are improved after surgery (Ghazi-Nouri et al. 2006).
10.4Specific Complications
¥Cataract appears in 47Ð80 % (Cherfan and Michels 1991; de Bustros et al. 1988c). For this reason, many surgeons will combine PPV with phacoemulsiÞcation cataract surgery rather than wait for the cataract to develop. This approach is recommended.
¥Damage to the internal limiting membrane and nerve Þbre layer may result (Maguire et al. 1990; Trese et al. 1983b).
¥Persistent cystoid macular oedema not responsive to IVTA.
¥Myopic postoperative refraction may occur because the elevation of the retina in the macula by an ERM may lead to a short axial length during biometry and the use of an overly powerful IOL. See the example of measurements from a patient who developed an ERM and who had prior biometry measurements.
|
|
After ERM |
|
Before ERM |
development |
Axial length (mm) |
23.93 |
23.27 |
Keratometry (D) |
42.27 |
42.27 |
IOL suggested power |
21.0 |
23.0 |
(D) |
|
|
Predicted refraction |
0 |
−0.06 |
(D) |
|
|
Refraction (D) at time |
0 |
+0.25 |
of biometry |
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¥Retinal tear and retinal detachment (Michels and Gilbert 1979) may occur in 2.5 %, although this is less commonly reported than for macular hole in which the posterior hyaloid membrane must be detached (Guillaubey et al. 2007). If PVD is induced, retinal tears have been described in 32.1 % compared to 2.1 % in those without induction of PVD (Chung et al. 2009).
Surgical Pearl of Wisdom
One of the complications of epiretinal membrane removal is the formation of a full-thickness macular hole. An epiretinal membrane is often accompanied by a lamellar macular hole or can cause cystoid macular oedema, which sometimes can be quite pronounced. Optical coherence tomography can help assess the amount of cystoid macular oedema and the morphology of the retina at the fovea. In cases of very marked macular oedema, the height of the cystoid spaces can cause thinning of the inner retina, therefore increasing the intraoperative risk of a lamellar or even full-thick- ness macular hole formation.
I have had two cases of epiretinal membrane removal that developed a posterior pole retinal detachment soon after vitrectomy due to an iatrogenic full-thickness macular hole. Both cases had a coexistent lamellar macular hole, which was documented preoperatively by optical coherence tomography. Both eyes were managed successfully with ßuidÐair and ßuidÐgas exchange alone. Since then, I have modiÞed my management of an epiretinal membrane.
At the end of vitrectomy, after the epiretinal membrane removal and examination of the retinal periphery for possible retinal breaks, I do a ßuidÐair or ßuidÐgas exchange using a 15 % SF6Ðair mixture, thus avoiding unnecessarily long tamponade duration. I do this in eyes with epiretinal membrane and coexisting lamellar macular hole or marked cystoid macular oedema with thinning of the inner retina. I also prefer to do it in pseudophakic or aphakic eyes to avoid the formation of postoperative cataract. Since then, I have not had any case of posterior pole retinal detachment due to iatrogenic full-thickness macular hole.
Vlassis Grigoropoulos, Henry Dunant Hospital,
Athens, Greece
10.6 Summary |
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Fig. 10.32 This long-standing macular pucker had distortion postoperatively despite adequate removal of the ERM. The postoperative OCT shows residual folding of the retina which has not resolved
Fig. 10.30 Damage to the macula after removal of ERM has caused a secondary CNV to form
Fig. 10.33 See previous Þgure
10.5 Membrane Recurrence
This has been shown to occur in 4Ð20 % of cases (Michels 1984; Grewing and Mester 1996; Park et al. 2003) but will respond to repeated surgery. Removal of the ILM has been reported to reduce recurrence (Park et al. 2003). After surgery, recurrence appears to be more common in secondary ERM, for example, in patients with retinal angiomata (30 %) (McDonald et al. 1996) and in uveitis (Verbraeken 1996).
Fig. 10.31 See previous Þgure
10.6Summary
Epiretinal membranes are usually easily removed; however, surprises can occur. Visual results can also be unpredictable with distortion improving more often that visual acuity.
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Fig. 10.34 ERM can recur after surgery as in this patient over
6 months postoperatively; removing the ILM may reduce recurrence
Fig. 10.35 See previous Þgure