Surgical Technique

Edited by George A. Williams

Degenerative Myopia: Myopic Macular Schisis and the Posterior Pole Buckle

S

afe and effective treatments are needed for degenerative myopia and its complications until a final genetic cure is found. The loss of vision is most commonly the result of myopic macular degeneration, the risks of which are functions of the eyes’ axial lengths and the patients’ ages.1 Myopic macular degeneration is the result of an inherited scleral abnormality.2 In an affected individual, the precursor of degenerative myopia appears as accelerated ocular growth during childhood. Subsequently, this is followed by episodes of intermittent scleral stretching that may continue throughout adult life. The influence of environmental factors is being increasingly recognized as relevant to the development of the phenotype, although the mechanisms involved are unknown at this time. Degenerative myopia occurs in eyes with axial myopia in excess of −6.00 diopters and axial lengths .26 mm. The prevalence of this condition in the population of the United States is reported to be approximately 2%; but the figure can be at least 10% in some regional groups in China, Singapore, and Japan. This high incidence in some Asian countries reflects the high prevalence of the genotype in their populations as well as some unknown environmental factors.1–3 To control a scleral disorder, it is reasonable to consider approaches that access that tissue directly. In a recent study of a surgical treatment for the control of progressive myopia, posterior pole buckles were shown to be able to constrain axial extension in adult eyes. In that reported series of 59 patients, one treated eye had preexisting macular schisis and tractional detachment, both of which were corrected by the buckling procedure.4 After this single example with a favorable outcome, other

eyes with schisis and tractional detachments have been treated by a modified version of the same technique. This work was motivated by the fact that scleral buckling would be an attractive alternative to the current treatment by vitrectomy and internal limiting membrane(ILM) peeling described first by Tano and Kishi in 1999.5 This report covers the outcomes of posterior pole buckling for the treatment of myopic schisis and macular detachments in 10 adult eyes. It is part of an on-going series. Method Of the 10 adult eyes with progressive high axial myopia, 8 had macular schisis, 2 eyes had both macular schisis and tractional retinal detachments, and 2 eyes had schisis plus a lamellar macular hole. The preoperative studies involved a complete eye examination, visual acuity measurement, photographic documentation, macular cross-sectional imagery by optical coherence tomography (OCT) (Zeiss-Humphrey, Dublin, CA) and axial length measurement by IOL-master (Zeiss-Humphrey). The same observations and measurements were made periodically during the postoperative follow-up examinations. Figure 1 is a schematic representation of a tensioned buckle in position over the posterior pole of a right eye. The tendency for the buckle to slip temporally is countered by careful selection of the anchor points to the recipient globe. The central portion of the buckle rests nasal to the inferior oblique muscle insertion and temporal to the optic nerve and the short posterior ciliary arteries. The placement technique was designed to avoid the eye trauma inevitably associated with the exposure of the posterior pole for scleral suture placement. The buckling elements were prepared from the sclera of donor eyes supplied by a regional eye bank. The material was fashioned into a strip at least 65 mm long and 10 mm wide in its middle third. The width of the strip was tapered to 5 to 6 mm at each end. The outer surface of the strip was marked with an ink stripe from a skin pencil, to enable the surgeon to be able to detect any twisting that might be inadvertently induced during the placement procedure.

From the *Retinal Diagnostic Center, Campbell, California; and †Department of Ophthalmology, Good Samaritan Hospital, San Jose, California. Part of this material was presented at the Squaw Valley Retinal Symposium, February 2011 and the Frankfurt Retina Meeting, Frankfurt, Germany, March 2012. The author has no financial or conflicts of interests to disclose. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.corneajrnl.com). Reprint requests: Brian Ward, PhD, MD, Retinal Diagnostic Center, 3395 South Bascom Avenue, Suite 140, Campbell, CA 95008; e-mail: [email protected]

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Surgical Procedure

Fig. 1. A diagram of anterior and posterior views of a right eye with an augmented posterior pole buckle in position.

Small and moderate degrees of schisis layer separation required no augmentation. However, eyes having larger degrees of posterior retinal layer separation, or tractional detachments, were treated by the addition of rectangular pillows for additional indentation at the posterior pole. They were secured to the underside of the central portion of the buckling strip by means of four 5-0 Dacron sutures (Surgidac SS24 Spatula, Covidien, Boston, MA). The dimensions of the pillows were 14 · 8 mm, with overall thicknesses ranging from 1.0 mm to 2.5 mm. The pillows consisted of either layered sclera (1.0 to 2.0 mm in thickness) or silicon sponges (2.0 to 2.5 mm in thickness). The band was given its initial tensioning during the tying of the sutures securing its ends to the recipient globe. Further tension could be produced by means of a variable tuck that could be created by means of two 5.0 Dacron sutures preplaced near the end of the strip anchored in the superonasal quadrant of the recipient eye (Figure 2).

Fig. 2. Two 5-0 Dacron sutures secure the end of the buckle to the recipient’s sclera. The band’s tension has been increased by tying-off a separate pair of pre-placed 5-0 Dacron sutures.

• The procedure is carried out under general anesthesia to avoid the creation of orbital edema by the injection of regional anesthetic fluids. A parasympathetic blocking agent is administered intravenously to prevent cardiac slowing that might result from the oculocardiac reflex. • A limbal peritomy is created, and blunt dissection is used to expose the scleral quadrants and the insertions of the four rectus muscles. Silk ties are passed under each of the muscles, to provide means for the manipulation and the stabilization of the globe, as required during the surgical procedure. • The insertion of the inferior oblique muscle is then visualized with the aid of both an “”Arruga spoon retractor (Bausch & Lomb-Storz, Bloomington, MN) and a strategically positioned operating light. The entire insertion is captured in the loop of a 00 silk tie. Any attachments between the muscles are cleared. This is a crucial step in providing a passageway through which the buckle may smoothly slide to the posterior pole. • Adhesions between the rectus muscles and the globe are then divided by passing a muscle hook between the bellies of the muscles and the globe. The medial rectus is excluded from this step. • The prepared buckling strip is then placed under the superior rectus muscle. Two 5-0 Dacron sutures had previously been preplaced near its nasal end to allow a tensioning tuck to be created later—if required (Figure 2). The two partial thickness bites taken for each preplaced tucking suture had been positioned 5 to 6 mm apart. • The end of the buckle is then secured to the outer layers of the recipient sclera by means of two white 5-0 Dacron sutures with spatula needles. The scleral bites are placed so that the anterior end of the intrascleral tunnel is 2 to 3 mm posterior to the line of insertion of the adjacent rectus muscles. • The free end of the strip is passed between the lateral rectus muscle and the globe, and then behind the insertion of the inferior oblique muscle. The final step is to pass the free end between the inferior rectus muscle and the globe so that it presents in the inferonasal quadrant of the orbit. The strip, previously marked on its outer surface with an ink stripe is then inspected to ensure that no accidental twisting has occurred during its passage around the eye. • At this point, the strip is positioned around the equator of the globe. Care must be taken that the free end does not slip posteriorly because its retrieval can be time consuming. The strip is then grasped in straight forceps, and a series of vertical elliptical movements

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are made with tension being applied to the band at the lowest point of each excursion. This movement is repeated until the central portion of the strip has slipped posteriorly over the temporal globe and rests over the posterior pole. When the eye is adducted, the anterior edge of the strip can be barely seen by placing the Arruga spoon over the lateral rectus or over the sclera of the inferotemporal quadrant of the globe. Once correct positioning has been verified, the strip is cut to length. Two 5-0 Dacron fixation sutures are passed through its end to secure it to the outer layers of the recipient sclera, with tunnels that begin 5 mm anterior to the cut strip and emerge behind the line of the rectus muscle insertions. Tension is created in the strip as these fixation sutures are tightened and tied-off. Attention is then turned back to the superonasal quadrant, where the anchoring sutures are checked and the tension in the buckle is assessed. If more tension is required, a tuck is created in the strip by tightening and tying-off the two preplaced sutures illustrated in Figure 2. The intraocular pressure is checked and a complete indirect ophthalmoscopic examination is performed. The perfusion at the optic nerve is verified and any change in the appearance of the fundus is noted. In cases where there is a deep posterior staphyloma, it may be possible to see a modest flattening of the center and the temporal parts of the posterior pole. The 0-0 muscle ties are then removed and Tenon capsule and the conjunctive are repositioned using 6-0 plain gut sutures. A broad-spectrum antibiotic/ steroid combination is then injected under the conjunctiva. Because temporary pressure increases and small choroidal effusions are relatively common after these procedures, intravenous doses of 500 mg of acetazolamide and 40 mg of Solumedrol are given. Atropine drops and a combination (steroid/ antibiotic) ointment are placed on the cornea. The eye is then padded closed and a metal shield is secured over the cotton pads (see Supplemental Digital Content, http://links.lww.com/IAE/A113).

drawn when the pressure is #17 mmHg without its use. A topical antibiotic/steroid combination drop is started on the first day after surgery and its use is tapered-off over a 3-week period. The patient is instructed to wear a spectacle correction on the day after the surgery. This is to encourage the early reestablishment of binocular fusion. Abduction exercises are given to hasten the recovery from the anticipated postoperative abduction deficiency. Results The outcomes of buckling for the correction of myopic macular schisis and detachment are presented as pairs of matched OCT in Figures 3 to 12. These pairs of images are arranged according to the nature of the presenting macular condition: 1. Figures 3 to 5 show maculae with small amounts of retinal schisis and ILM avulsions. 2. Figures 6 to 8 show predominantly outer layer retinal schisis. 3. Figures 9 and 10 show schisis and neurosensory retinal detachment. 4. Figures 11 and 12 show schisis with an inner layer (lamellar) macular hole. Preexisting ILM avulsions and limited areas of retinal schisis are evident in Figures 3 to 5. The retina is thicker away from the areas of spontaneous ILM avulsion. After buckling, generalized tissue thinning is seen along with the closure of ILM avulsions.

Postsurgical Care After surgery, oral prednisone is taken for 6 days to reduce orbital congestion and swelling. It also minimizes any small choroidal effusion that might occur. Acetazolamide is taken orally until the intraocular pressure is ,17 mmHg, off the medication. A topical pressure control agent is frequently substituted for the acetazolamide on the second day. This is with-

Fig. 3. A central “cystic” central macular schisis with a segment of avulsed ILM (Table 1; Patient 1).

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Redundancy in an avulsed ILM in Figure 3 is illustrative of its relative inelasticity. Figures 6 to 8 show considerable retinal thinning after buckling. These three cases had originally presented with wide bands of posterior retinal schisis. The band of schisis, tissue “separation” or “rarefaction” appears to be at the anatomical level of the outer plexiform layer, except at the center of the macula where most of the tissue anterior to the receptor layer seems to be involved.

Figures 11 and 12 exhibit very different degrees of retinal schisis but have the common feature of an inner layer retinal discontinuity (a lamellar macular hole). In these cases, the ILM has been interrupted at the center of the macula. This break in the ILM may result from processes related to local vitreous traction. Buckling resulted in some minimal decrease in the diameter of the inner retinal hole. The broad posterior schisis layer evident in Figure 12 showed only about a one-third reduction in thickness after buckling. In contrast, the anterior retinal schisis evident in the same case responded by closing. Signs of radial neural or supporting tissue elements are present within the broad posterior schisis “cavity” in Case 10 (Figure 12). Some functionality of these stretched retinal elements is attested to by the surprisingly good levels of visual acuity recorded in this case (20/30−). Posterior pole buckling resulted in modest visual acuity improvements in four patients. Table 1 shows the increases in visual acuity (at least 2 lines of improvement on the Snellen chart) achieved by these 4 eyes (Cases 4, 6, 7, and 8). Both the eyes presenting with tractional retinal detachments and macular schisis are seen to be members of this group Cases 7 and 8). The visual acuities of all the eyes were limited, to some extent, by the presence of some degrees of degeneration resulting from other myopic processes, and in some cases media opacities affected the acuities recorded. No vision loss, infection, or any other serious complication occurred in any eye in this series.

Fig. 5. Anterior retinal schisis and an ILM avulsion (Table 1; Patient 3).

Fig. 6. Posterior schisis in the nasal macula in a left eye (Table 1; Patient 4).

Fig. 4. Partially avulsed ILM and anterior retinal schisis (Table 1; Patient 2).

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Fig. 7. Chronic posterior retinal schisis (Table 1; Patient 5).

No patient experienced prolonged diplopia after the surgery. Discussion

However, the correlation between the appearance of the OCT image and the functional integrity of the retinal tissue remains largely conjectural. In some cases, visual functioning seems to be largely intact in contrast to the impression that might be gained from a cursory examination of the OCT images of the macula. Schisis usually occurs in eyes that have axial lengths .28 mm. However, it may also occasionally be seen in eyes with axial lengths as short as 26 mm, especially in globes having relatively small equatorial diameters but with a deep, sharply circumscribed central staphylomas. Retinal schisis frequently coexists with other forms of myopic maculopathy and other ocular abnormalities. However, myopic avulsions, schisis, tractional detachments, and some macular holes may be usefully looked upon as being members of a particular neural disruptive group of myopic macular features. In this case, myopic macular degeneration may be considered to have three clinically recognizable components. All of them being results of various forms of structural damage to the choroid, the retina, and any attached cortical vitreous:

Myopic macular schisis may be evident on slit-lamp examination, but an OCT, or some other equivalent image, is required for the analysis of its structural details.

a) Atrophic degeneration (direct cellular damage to the tissues of the macula). b) Exudative degeneration (choroidal membranes, subretinal fluid (serous or hemorrhagic), and scarring.

Fig. 8. Chronic posterior retinal schisis (Table 1; Patient 6).

Fig. 9. Schisis and macular detachment (Table 1; Patient 7).

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In the 10 subjects presented in this study, posterior pole buckling reduced or eradicated macular schesis in all cases. The buckle’s force on the posterior sclera seems to relax anterior directed forces from the ILM, epiretinal membranes, and any adherent vitreous cortex. The buckling force also opposes the posteriordirected forces on the outer retina derived from the

stretching of the scleral shell. A variable rate of correction of the schisis was observed, with several months being required in some of the earlier cases treated with unaugmented buckles (Figures 4–6). The overall efficacy of buckling was least in a case of long-standing posterior retinal schisis with marked separations of the retinal layers and a large inner layer lamellar hole (Figure 12). Here, buckling caused about a 30% reduction in the thickness of the outer schisis but was more effective in correcting anterior layer schisis and ILM avulsions. The lamellar holes in Figures 11 and 12 became somewhat smaller after buckling, perhaps because of relaxation of tension in the stretched ILM. A visual acuity of 20/30− in this eye indicates a reasonable level of residual functioning of the receptors and stretched neurons as well as the tissues supporting them. Whether the anterior retinal hole provides any relevant “fluid communication” between the posterior schisis layer and vitreous fluid is unknown. An examination of the pre- and postoperative OCT images suggest that retinal disruption first begins as the ILM reaches the limit of its elasticity, whereas the outer retina continues to be dragged posteriorly by progression of the axial myopia. In the normal course of events, axial extension is seen to produce a thinning of both the choroid and the retina. Yet, in many highly myopic eyes, a local thickening of the neural retina is seen before the appearance of schisis. This may well be an early sign that radial forces are developing across the layered retinal tissue. The recognition of such a “preschisis” stage would allow treatment to be

Fig. 11. Anterior schisis with anterior lamellar break (Table 1; Patient 9).

Fig. 12. Chronic schisis with large anterior lamellar break (Table 1; Patient 10).

Fig. 10. Schisis and macular detachment (Table 1; Patient 8).

c) Neural disruptive degeneration (tractional schisis, ILM avulsions, macular holes [full or partial thickness], and tractional retinal detachments).

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RETINA, THE JOURNAL OF RETINAL AND VITREOUS DISEASES  2013  VOLUME 33  NUMBER 1 Table 1. A Summary of Patient Information for the 10 Cases Presented Axial Length (mm)

Visual Acuity

Subject

Age

Sex

Before

After

Before

After

Augmentation

Follow-up (Months)

1 2 3 4 5 6 7 8 9 10

67 48 66 70 47 53 66 74 51 47

AM CM CF AF AF AF CF CF CF CM

29.8 29.7 29.5 29.0 30.0 32.6 30.0 28.2 27.0 30.9

29.4 29.0 29.3 28.7 29.7 32.6 30.0 27.8 27.0 30.4

20/50− 20/40− 20/30− 20/30+ 20/30− 20/70− 20/300 20/80− 30/30− 20/30−

20/50 20/25 20/25 20/30 20/25− 20/50− 20/125 20/50− 20/25− 20/30−

None Sclera Sclera Sclera None Sclera Sponge Sclera None Sclera

6 19 16 24 44 22 14 72 12 03

R L R L L R R L L L

AM, Asian male; AF, Asian female; CM, Caucasian male; CF, Caucasian female; L, left eye; R, right eye.

considered before a point of more obvious macular tissue breakdown. The treatment of macular schisis by buckling avoids some of the risks of the intraocular procedure. However, where detachment or preretinal fibrosis remain after buckling, vitrectomy and membrane peeling can be helpful. The ideal physical properties required of the material for this buckling procedure include ease of manipulation, flexibility, limited elasticity, smooth surface texture, and absence of the risk of an edge cutting into the recipient’s weak sclera (cheese-wiring). These properties have been sought after in numerous natural tissues and manufactured implantable materials. However, to date, donor sclera has met most of these requirements; and it remains the material of first choice. The recent introduction of gamma irradiation for sclera preservation means that this tissue no longer requires very complicated handling and deep freezing for its preservation. In the irradiated form, scleral tissue may have a shelf life of up to 2 years (at room temperature). All donor tissue must be tested and certified free of potential pathogens according to accepted eye bank procedures and protocols. After surgery, all eyes have a temporary abduction deficiency with diplopia that is usually symptomatic for only a few days. In some cases, however, it may persist for longer time. Patients are prepared for this possibility as part of the informed consent process. To minimize the period of diplopia, patching stops on the day after surgery and abduction exercises are begun. To encourage the early reestablishment of binocular fusion, a spectacle correction is also used from the first day after surgery. Patients with a preexisting strabismus must be made aware of the possibility that the angle of that strabismus may change after surgery, presumably on the basis of orbital scarring affecting an eye that has limited rotational movements.

It has been concluded, from the experience to date, that the most shallow schisis plane separations require no augmenting pillow at the posterior pole. Wider posterior retinal schisis cavities seem to be an indication for 1.0-mm to 2.0-mm-thick pillows of sclera or silicon sponge to be used. Broad schisis separations and all tractional retinal detachments do benefit from the additional buckling effect provided by 2.0-mm to 3.0-mm-thick sponge pillows. Wherever a spontaneous separation of the ILM occurs, it is seen that the retina tends to resume its stretched and thinned myopic appearance, and closure of local schisis planes can occur. Surgical vitrectomy with ILM peeling was designed to induce the same result. However, this approach to the treatment of myopic macular schisis does involve some risks inherent in the direct manipulation of the physically weak retinal tissue. Regarding the use of vitrectomy, another fact to consider is that ILM peeling does nothing to prevent the retina and choroid from continuing to be dragged posteriorly by progressive elongation of the globe. Buckling offers the opportunity of relieving myopic macular traction while also limiting axial myopia progression. The control of the axial myopia may help to minimize future macular degeneration and stabilize the power of lenses required for the eye’s refractive correction.

Conclusion Macular schisis and tractional macular detachments are the result of forces applied across the retina by scleral growth and stretching. The extension of the sclera applies a posterior force to the outer retina while the inner retina is subjected to a constraining anterior force derived from its relatively inelastic ILM. Posterior pole buckling relaxes these forces, and in doing so, reduces or corrects macular schisis and tractional detachment.

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Buckling the posterior pole before schisis occurs may well prevent its occurrence while at the same time limiting axial myopia progression and hopefully minimizing future myopic macular degeneration. The stabilization of axial myopia prolongs the effectiveness of any refractive correction, whether provided by external optical devices or by surgically induced refractive changes. Four of the 10 eyes in this study showed some visual acuity improvement. Although the stabilization of the neural destructive complications of the myopic maculopathy was the primary goal of this work, the achievement of some short-term visual acuity increases, in some of the eyes, is gratifying. On the basis of our experiences of posterior pole buckling, this procedure has now become our primary treatment modality for these neural destructive complications of degenerative myopia. Key words: degenerative myopia, lamellar macular hole, macular buckles, macular degeneration, macular

hole, macular schisis, malignant myopia, myopic macular degeneration, myopic macular schisis, myopic macular traction, pathological myopia, progressive myopia, retinal schisis, tractional macular detachment. BRIAN WARD, PHD, MD*† References 1. Curtin BJ. The Myopias. Philadelphia, PA: Harper & Row; 1985:10;237–239. 2. Mc Brien NA, Gentle A. Role of the sclera in the development and pathological complications of myopia. Prog Retin Eye Res 2003;32:307–388. 3. Tano Y. Pathological myopia: where are we now? Am J Ophthalmol 2002;134:645–660. 4. Ward B, Tarutta EP, Mayer MJ. The efficacy and safety of posterior pole buckles in the control of progressive high myopia. Eye (Lond) 2009;23:2169–2174. 5. Takano M, Kishi S. Foveal retinoschisis and retinal detachment in severely myopic eyes with posterior staphyloma. Am J Ophthalmol 1999;128:472–476.