Scleral buckling for rhegmatogenous retinal detachment
Article summary goes here.
= Disease Entity = Rhegmatogenous retinal detachment
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The essential requirements for a rhegmatogenous retinal detachment include a retinal break (rhegma = rent or rupture) and vitreous liquefaction sufficient to allow fluid in the vitreous csavity to pass through the break(s) into the subretinal space. The usual pathological sequence that results in retinal detachment is vitreous liquefaction followed by a posterior vitreous detachment (PVD), which in turn causes retinal tears at the sites of significant vitreoretinal adhesions (Figure 1). In a smaller but significant percentage of cases, a complete PVD does not occur, and vitreoretinal traction occurs in regions of the retina that are near breaks unrelated to the partial PVD. All ocular conditions that are associated with an increased prevalence of vitreous liquefaction and PVD or with an increased number or extent of vitreoretinal adhesions are associated with a higher incidence of retinal detachment.
The majority of eyes with retinal breaks do not develop retinal detachment because normal physiological forces keep the retina in place. However, the combination of retinal breaks, vitreous liquefaction and detachment, traction on the retina (vitreoretinal traction), and intraocular fluid currents associated with movement of liquid vitreous and subretinal fluid can overwhelm these "attachment factors", causing retinal detachment.
Major risk factors have in common an increased incidence of retinal break(s), vitreous liquification and detachment, and abnormal vitreoretinal adhesions. Specific entities include myopia, surgical and non-surgical trauma, lattice degeneration, infectious retinitis, and hereditary vitreoretinal disorders.
As noted above, retinal detachment occurs when the combination of factors that promote retinal detachment overwhelms the normal attachment forces. This is due to a combination of retinal breaks, vitreous changes, and intraocular fluid currents.
Retinal breaks are traditionally classified as holes, tears, or dialyses. Retinal holes are full-thickness retinal defects that are not associated with persistent vitreoretinal traction in their vicinity. They usually occur as a result of localized atrophic intraretinal abnormalities. Retinal tears are usually produced by PVD and subsequent vitreoretinal traction at sites of significant vitreoretinal adhesions. Vitreous traction usually persists at the edge of a tear, which promotes progression of the retinal detachment. Dialyses are linear retinal breaks that occur along the ora serrata. Although most are associated with blunt ocular trauma, dialyses can occur spontaneously.
Aging of the human vitreous (synchysis senilis) is characterized by liquefaction of the vitreous gel and progressively enlarging pools of fluid (lacunae) within the gel. These optically empty liquid spaces coalesce with ageing; extensive liquefaction within the vitreous cavity leads to a reduction in both the shock-absorbing capabilities and the stability of the gel. Posterior vitreous detachment (PVD) usually occurs as an acute event after significant liquefaction of the vitreous gel. The precipitating event is probably a break in the posterior cortical vitreous in the region of the macula.2 This is followed by the immediate passage of intravitreal fluid into the space between the cortical vitreous and retina. Characteristically, this rapid movement of fluid and the associated collapse of the remaining structure of the gel result in extensive separation of the vitreous gel and retina posterior to the vitreous base, especially in the superior quadrants. Partial PVDs usually progress rapidly (within days) to become complete, although they do not always separate from the entire posterior retina. Vitreoretinal traction has a number of causes, which range from simple action of gravitational force on the vitreous gel to prominent transvitreal fibrocellular membranes. Gravitational force is important and probably accounts for the high percentage of superior retinal tears (80%). However, rotational eye movements, which exert strong forces on all vitreoretinal adhesions, are probably more important causes of ongoing vitreoretinal traction. When the eye rotates, the inertia of the detached vitreous gel causes it to lag behind the rotation of the eye wall and, therefore, the attached retina. The retina at the site of a vitreoretinal adhesion exerts force on the vitreous gel, which causes the adjacent vitreous to rotate. The vitreous gel, because of its inertia, exerts an equal and opposite force on the retina, which can cause a retinal break or separate the neural retina farther from the pigment epithelium if subretinal fluid is already present (Figure 2). When the rotational eye movement stops, the vitreous gel continues its internal movement and exerts vitreoretinal traction in the opposite direction.
Continuous flow of liquid vitreous through a retinal break into the subretinal space is necessary to maintain a rhegmatogenous retinal detachment, because subretinal fluid is absorbed continually from the subretinal space via the RPE. Trans-break flow is encouraged by vitreoretinal traction, which tends to elevate the retina from the RPE. Rotary eye movements cause liquid currents in the vitreous to push against the gel adjacent to the retinal break and to dissect beneath the edge of a retinal break into the subretinal space (Figure 2)Subsequent eye movements also have an inertia effect on the subretinal fluid that favors extension of the retinal detachment.
Attempts to prevent retinal detachment have been advocated for many decades, but the value of such interventions remains questionable in most instances. (This subject is dicussed in more detail in another Eye Wiki manuscript.) The American Academy of Ophthalmology Preferred Practice Pattern on the topic (ref) contains only a single evidence-based recommendation for prophylactic therapy. This is in regard to the proven value of treating symptomatic retinal tears associated with persistent vitreoretinal traction.
= History=: The early symptoms of acute retinal detachment are the same as those of an acute PVD: the sudden onset of tiny dark floating objects, frequently associated with photopsia (flashes). Photopsia are usually brief, in the temporal visual field, and are best seen in the dark and associated with eye movement.
Loss of visual field does not occur until sufficient subretinal fluid has passed through the retinal break(s) to cause a retinal detachment posterior to the equator. The majority of retinal breaks are located at the equator or more anteriorly; subretinal fluid initially accumulates in the retinal periphery, where it causes a corresponding loss of peripheral vision in the area that is related inversely to the location of the retinal detachment. The loss of peripheral vision (a “curtain effect”) increases as the detachment enlarges; central visual acuity is lost when subretinal fluid passes beneath the macula. Frequently, patients do not notice any symptoms until the macula becomes involved.
= Diagnosis= If the retina can be well visualized, the diagnosis of rhegmatogenous retinal detachment is made on the basis of clinical examination. In eyes with opaque media, the presence of a retinal detachment is usually determined ultrasonographically; the location and identification of the causative retinal breaks are based upon the configuration of the detachment as well as on the patient’s history and associated findings. The vast majority of retinal detachments are diagnosed easily with a binocular stereoscopic evaluation of the entire retina. Areas of retinal detachment are recognized by elevation of the neural retina from the RPE and loss of pigment epithelial and choroidal detail beneath the elevated retina. Retinal breaks are also discovered by direct examination. Indentation of the peripheral retina (scleral depression) is employed to facilitate visualization of the anterior retina at different angles, and this improves abilities to identify all retinal defects.
Retinal breaks associated with small amounts of subretinal fluid may be difficult to detect; however, the diagnosis becomes more obvious as the retinal detachment increases in size. A stereoscopic vitreoretinal examination typically reveals an elevated sensory retina in the area of detachment, but the critically important identification of all retinal breaks may remain difficult—it is considerably easier to diagnose the retinal detachment than to detect all retinal breaks. Due to the effects of gravity, the topography of a retinal detachment is of major value in the prediction of the most likely locations of retinal breaks.10 Retinal breaks are usually present superiorly within the area of detachment. Thus, if a retinal detachment involves one upper quadrant or both the superior and inferior quadrants on one side of the vertical meridian, the responsible retinal break is likely to be near the superior edge of the detachment. Retinal detachments that involve the inferior quadrants tend to follow the same rules, but the progression of the detachment is often much slower, and symmetrical spread of subretinal fluid may occur on both sides of the break. Therefore, detachments that involve one or both inferior quadrants may have a break near a superior margin of the detachment or in the meridian that bisects the area of detachment. Nevertheless, because multiple retinal breaks are common, the entire periphery of the detached retina must be meticulously examined.
= Differential diagnosis = Retinal detachments that occur as a result of retinal breaks must be distinguished from several conditions in which retinal blood vessels are clearly separated from the pigment epithelium. These include retinal detachments from other causes and retinoschisis. Choroidal lesions that elevate the overlying retina and intravitreal pathology that simulates an elevated retina may also be confused with retinal detachment.
The distinction between different types of retinal detachment can be difficult in eyes with small or undetectable retinal breaks and features associated with intraocular proliferation or exudation. In some cases, both a rhegmatogenous and a traction or exudative component may be important in the pathogenesis of the detachment. This is particularly common in eyes with proliferative diabetic retinopathy and retinal detachment. Pure traction detachments usually have a concave surface, and the shape, location, and extent of the detachment can be accounted for by the evident vitreous traction (see Fig. Diabetic retinal detachments with a rhegmatogenous component are usually more extensive and often have a convex contour. Exudative detachments from a variety of causes are characterized by shifting subretinal fluid, which assumes a dependent position beneath the retina. In most cases, the fluid is located inferiorly and its cause within or beneath the retina may be apparent or quite subtle.
Rhegmatogenous reteinal detachment are indications for surgery. The three major surgical methods include scleral buckling, vitrectomy, and pneumatic retinaopexy (PR), and combinations of all three are frequently employed.
This manuscript will discuss scleral buckling, and Eye Wiki manuscripts regarding the alternatives are available.
Localized indentation of the sclera, choroid, and pigment epithelium beneath a retinal break alters the anatomical and physiological factors associated with the production of a retinal detachment. The fundamental goal of scleral buckling is the functional closure of all retinal breaks, so that normal physiological forces can maintain a permanent state of attachment. Drainage of subretinal fluid and scleral buckling will usually close the responsible break(s) immediately. In a non-drainage procedure, functional closure of retinal breaks can result from several beneficial effects of a scleral buckle, including (1) reduction of vitreoretinal traction by displacing the eye wall and retina centrally; (2) displacement of subretinal fluid away from the location of the retinal break and scleral buckle; (3) postoperative increase in the height of the scleral buckle; (4) approximation of the retinal break and adjacent vitreous gel; (5) increase in resistance to fluid flow through the retinal break, with consequent increase in the relative reattachment forces; and (6) alteration in the concave shape of the eyeball, resulting in a change in the effect of intraocular currents that encourage liquid vitreous to enter the subretinal space. These effects are non-exclusive and probably synergistic, and they are also important in drainage cases. Although contemporary scleral buckling procedures routinely include the creation of a chorioretinal burn, such an adhesion is not always necessary to maintain retinal reattachment.
Principles of scleral buckling
The most important skill required in surgery for retinal detachment is the ability to detect all retinal breaks and additional areas of vitreoretinal pathology. Scleral buckling is performed to produce functional closure of retinal breaks responsible for retinal detachment and to reduce the chances of recurrent detachment. Various kinds and shapes of silicone rubber are used, including segments of silicone sponge as well as solid silicone shaped into bands for encircling the eye and into additional forms to augment the width and height of the buckle in selected areas. The specific configuration of the scleral buckle depends upon a number of factors. Following localization and treatment of retinal breaks and areas of vitreoretinal degeneration, the silicone buckling element is secured to the scleral surface, usually with sutures. Drainage of subretinal fluid is performed in the majority of cases. Intravitreal gas injection is sometimes employed in conjunction with scleral buckling. Problems encountered at any point of the procedure may require modifications in technique.
Scleral buckle configuration
The location, number, size, and types of retinal breaks are important variables affecting the selection of a specific buckling technique. Similarly, the presence of vitreoretinal degeneration, with or without retinal breaks, and of significant vitreoretinal traction unassociated with retinal breaks should be considered in the preoperative assessment. If retinal breaks, vitreoretinal degenerative disorders, and significant vitreoretinal traction are present in multiple quadrants, a circumferential buckle is usually favored. A single retinal break unassociated with additional significant problems is usually managed with an isolated segmental buckle, if not with pneumatic retinopexy. The anterior-posterior dimensions of retinal break(s) and areas of significant vitreoretinal degeneration and vitreoretinal traction are also important considerations in planning a buckling procedure. Scleral buckles should support all edges of the retinal breaks and associated areas of vitreoretinal degeneration. In general, the buckling effect should extend into the zone of the vitreous base to eliminate current and future traction forces..
The internal changes caused by scleral buckling are determined by the size, shape, and consistency of the buckling material, the width of the suture bites placed to attach the silicone rubber to the sclera, the tightness of the tied sutures, and the extent to which an encircling element is tightened. A scleral buckle is associated with a significant displacement of intraocular volume. In order to avoid a large increase in intraocular pressure, drainage of subretinal fluid, paracentesis, or removal of liquid vitreous is usually necessary, particularly in eyes with compromised aqueous outflows and in those in which recent anterior segment surgery has been performed.
The scleral buckling operation
The procedure involves routine prepping and draping, conjunctival incision, identification and treatment of all retina breaks and areas of vitreoretinal degeneration, suturing buckling material to the sclera, and additional techniques as indicated.
Prep and Drape
For scleral buckling, the face, eyelids, and conjunctiva are prepared with appropriate antiseptic techniques, and the drapes are applied. A plastic adhesive drape is placed over the opened lids so that the drape adheres to the margins of the eyelids that are held securely in place with the eyelid speculum.
Conjunctival incision and isolation of rectus muscles
A 360 degree limbal conjunctival incision is usually made for encircling procedures, but a less extensive incision is performed for limited buckling procedures. A five clock-hour peritomy is usually sufficient for a quadrantic detachment when a radial or short circumferential buckle is planned, and only the two rectus muscles bordering the involved quadrant are isolated in this situation. Traction sutures are placed beneath the insertions of the exposed rectus muscles to facilitate positioning the globe. Rather heavy suture material, such as 2-0 silk, is recommended. After the traction sutures are placed, the sclera should be examined. It can be exposed for inspection by rotating the globe with two adjacent traction sutures and pushing the intermuscular fascia posteriorly with a cotton-tipped applicator. The surgeon should look for abnormalities such as anomalous vortex veins or scleral thinning. Thinning is usually seen as radial gray lines in the equatorial or preequatorial area, particularly superior temporally. These lines are called radial staphylomas, scleral cracks, or scleral dehiscences.
After examination of the sclera, the surgeon should carefully examine the retina 360 degrees with binocular indirect ophthalmoscopy and scleral indentation. Important lesions that were not noted preoperatively may become apparent, and occasionally this examination reveals significant changes that have developed since the preoperative examination.
Localization of retinal breaks
A localizing mark is made with a scleral marking device on the point of sclera overlying an edge of the retinal break(s). The tip of the scleral marker is firmly pressed against the eye for a few seconds, and the pressure creates a temporary black mark on the sclera. Alternatively, a flat diathermy probe can be used, yielding a light burn. The localization site is immediately dried and touched with a marking pen, because the pressure effect or light scleral burn disappear quickly. If a break is large, marks should ideally be placed at the posterior, anterior, and lateral margins. For smaller, routine tears, some surgeons prefer to localize with a single mark placed at the center of the anterior edge of the tear, preferring this location because (1) the anterior edge is the usual site of persistent vitreoretinal traction, (2) the anterior edge is always easier to mark than the posterior border, (3) a buckling effect extending from the anterior edge into the area of the vitreous base is desirable, and (4) it is relatively easy to estimate the amount of buckling effect required more posteriorly to support the respective break(s). Other surgeons prefer a single mark placed at the center of the posterior edge of the tear to help ensure that no part of the tear falls too far back on the posterior slope of the buckle. When positioning the buckle relative to the mark, the surgeon must keep in mind whether the posterior or anterior edge of the tear was marked.
Accurate marking is easily performed if the detachment is sufficiently flat to allow the retinal pigment epithelium to be pressed inward against the sensory retina. If the detachment is highly bullous, this is not possible and the surgeon must try to compensate for the parallax effect. With bullous detachments, the tendency is to localize the break too far posteriorly. If the surgeon is aware of the problem, an adequate anterior compensation can be made.
Thermal treatment of retinal breaks
A variety of methods have been employed to irritate the choroid and pigment epithelium so that chorioretinal adhesions seal retinal breaks. The three most popular techniques, which have persisted for many years, are diathermy, cryotherapy, and laser photocoagulation.
Diathermy is no longer employed by most surgeons. It should only be applied through thinned sclera, beneath partial-thickness scleral flaps, to avoid full-thickness destruction of sclera and achieve a more uniform intraocular reaction. The surgeon may apply the diathermy while inspecting the retina with the ophthalmoscope, limiting the intensity to that required to produce a moderately white lesion in the retina. Alternatively, an experienced surgeon can apply diathermy without ophthalmoscopic control, predicting the probable ophthalmoscopic result on the basis of the scleral reaction. Diathermy burns are spaced approximately 1.5 mm apart, producing intermittent pigmentary changes in the fundus that have been referred to as “leopard skin.”
Cryotherapy has gained wide acceptance since its reintroduction in 1964. A survey of retinal surgeons revealed that the vast majority of surgeons now employ it for most buckling cases. Although it is possible to apply cryotherapy beneath partial-thickness scleral flaps, it is not necessary to do so. The goal of cryotherapy is to apply contiguous lesions completely surrounding each retinal break and areas of vitreoretinal degeneration. A single row of confluent freeze spots is generally sufficient, although more than one row may be required anteriorly to extend the future adhesion into the vitreous base.
Cryotherapy should be applied while observing the retina with the ophthalmoscope. A prominent white change develops at the area of retinal freezing. The freezing is generally terminated soon after the surgeon observes the appearance of an ice ball approaching the neurosensory retina. In bullous detachments, the ice ball is not allowed to reach the retina itself, and the freezing of the retinal pigment epithelium is discerned by a change of color to dull orange or gray. If portions of the break remain highly elevated during scleral depression with the cryo probe, treatment can be postponed until some of the subretinal fluid is drained.
A challenge with using cryotherapy is that one cannot determine what areas of the retina have been treated for many minutes to days following treatment. This can lead to over treatment if sequential freezes overlap significantly, and this excessive therapy should be avoided. However, if the burns are not confluent in appropriate areas, an inadequate adhesion will result. Thus the surgeon must form an optimal visual image of the precise limits of prior applications of cryotherapy, and considerable experience is usually required to master this technique. Cryotherapy burns should extend only to the edges of medium and large retinal breaks from retina surrounding them. If the pigment epithelium lying beneath the break is included in the cryo burn, an intravitreal dispersion of pigmented cells capable of proliferation can occur. For the same reason, scleral depression of a treated area at the edge of a break should not be repeated after the treatment, and localization of retinal breaks should always precede cryotherapy.
Laser photocoagulation is not usually used to induce adhesive lesions in scleral buckling surgery for detached retina, because the retinal pigment epithelium is not sufficiently close to the retina to cause a burn. Although the surgeon can close retinal breaks with scleral buckling and/or intravitreal gas and then attempt to apply laser photocoagulation, this is usually easier a day or so following the operation when the retina is quite flat. Attached retinal breaks may sometimes be lasered intraoperatively with the laser indirect ophthalmoscope.
Use of buckling materials
Various materials have been used for scleral buckling, including fascia lata, palmaris tendon, plantaris tendon, knee cartilage, donor sclera, dura mater, polyviol, polyethylene, encircling nonabsorbable and absorbable sutures, gelatin, hydrogel, and silicone. The latter is far the most popular. It is a soft, synthetic rubber material that is nontoxic and nonallergenic. It is produced in a variety of molded shapes that can be modified by the surgeon and used in either solid or sponge form. Implants can be placed within the sclera or on its surface. Although they are not technically “implants” in the latter position, the term has persisted for decades and will be employed in this Monograph. Episcleral implants are currently employed in the vast majority of cases. These can be segmental or encircling in configuration.
Segmental episcleral buckles
Segmental silicone exoplants are secured to the sclera with 5-0 non-absorbable synthetic mattress sutures attached to spatula needles with cutting tips. One-half to two-thirds thickness intrascleral passes at least 6mm long are usually attempted for sponges and broad exoplants, whereas shorter intrascleral passes can be used to support encircling bands. The surgeon applies focal pressure with a cotton applicator near the intended suture site to prevent buckling of the sclera in front of the needle as it is passed through the sclera. Alternatively, a nearby muscle insertion can be grasped with a forceps to provide increased stability and to elevate intraocular pressure. The location of the needle tip should be visualized at all times during its passage through the sclera. Localized scleral buckles may be radially or circumferentially oriented, and a combination of the two may be considered if more extensive buckling is required. Radial scleral buckles provide focal support for a retinal tear and minimize the development of radial retinal folds commonly associated with circumferential buckles, which shorten the circumference of the eye wall but not the circumference of the retina. Circumferential buckles provide a zone of support oriented parallel to the region where vitreous traction is usually most severe, and they are an efficient means of supporting multiple areas of vitreoretinal pathology. When tightened, the sutures indent the exoplant and underlying eye wall. Using an exoplant of a given shape, the height of the buckling effect is determined by the distance between the suture bites and the tightness of the sutures when they are tied. Calipers may be used to measure the distance between the suture bites, and in general these should be 2-3 mm wider than the exoplant for a modest buckling effect and 4-8 mm wider for a relatively high buckle.
When a radially oriented segmental buckle is needed, intrascleral suture limbs are placed parallel to the meridian of the retinal break and equidistant from its edges, and the needle is passed so that the knot can be tied posteriorly (Figure 5-7). The size and type of the retinal break usually dictate the width and length of the exoplant. In general, the width of the silicone element should be at least as wide as the edges of the break marked on the sclera, and the buckle length should support both the posterior end of the break and the vitreous base anterior to the break.
If a circumferentially oriented segmental buckle is required, suture limbs are placed parallel to the limbus. The anterior bite is usually placed just anterior to the posterior margin of the vitreous base, a location estimated as lying about 2-3 mm posterior to an imaginary line drawn between the muscle insertions (and forming a portion of the spiral of Tillaux). A silicone element of sufficient width to support both the anterior and posterior edges of the retinal break(s) or other pathology is used, and the posterior suture bite is placed in a position that will produce an optimal buckling effect.
<3>Encircling episcleral buckles
If a 360 degree encircling circumferential buckle of modest width and height is needed, an encircling #240 , #41, #42, or other silicone band is passed around the circumference of the globe and beneath the rectus muscles. The band is traditionally anchored with a single mattress suture with bites parallel to the limbus placed in the center of each quadrant. Although they are an elegant and effective means of securing a band, scleral tunnels are usually not employed by most surgeons. Suture bites that straddle a silicone band should be placed just far enough apart to allow the band to move freely beneath the suture, and this distance equals the width of the band plus two-times its thickness (Figure 5-8). Narrower bites inhibit circumferential movement of the band, particularly if the sutures are pulled tight. Wider bites will allow the band to move anterior to its desired location when its ends are joined. In its proper position, the band is usually intended to support breaks in the region of the posterior edge of the vitreous base, and these are marked and treated before suture placement. In quadrants without retinal breaks, the vitreous base margin can be marked, or its location can be estimated and the anterior suture bite placed about 2-3 mm posterior to the imaginary line mentioned above. If a grooved segment of silicone tire is required because of a need for more extensive augmentation of the buckle, additional sutures may be required, depending upon the characteristics of the specific case. If a high broad 360-degree encircling scleral buckle is required, two broad mattress sutures are placed in each quadrant to accommodate a silicone tire and an overlying silicone band (Figure 5-9). The anterior suture bite is placed at the estimated location of the ora serrata, and the posterior bite is placed far posteriorly, at a spot dictated by the width of the tire, the desired amount of indentation, and the location of tears. Frequently, this distance is equal to twice the distance from the anterior bite to the marked posterior edge of the retinal break(s). If a vortex vein must be avoided with the posterior suture bite, two small circumferential passes can be made on either side of the vessel. When using segmental scleral buckles produced by circumferentially oriented silicone materials, suture bites are always placed in the location overlying the responsible retinal break(s), because the maximum buckle height is produced in this spot. However, if an increased buckling effect is needed in only a small area in a case in which an encircling band is employed, anchoring sutures are placed away from the important pathology, and a radially oriented piece such as #103 or #106 element is placed beneath the band and usually not sutured. The ends of an encircling band are joined with a silicone Watzke silicone sleeve, tantelum clip, or suture. Tantalum clips appear to be less popular than the sleeve, primarily because of the extra time required for their use, particularly if later adjustment of the length of the band is required. Some degree of twisting of the band near the elastic sleeve can occur when the band is tightened, and this can be avoided by grasping each end near the sleeve and by keeping the ends flat against the periscleral portion already in place. The ends should be rejoined if twisting causes a narrow edge of the band to indent the sclera, as this can lead to later intrusion problems. Since even minimal twisting of the sleeve can affect the inner morphology of the buckling effect, the sleeve should be located in a quadrant relatively free of significant vitreoretinal pathology. Alternatively, a 5-0 suture tied in a loop around the overlapped ends of the encircling band minimizes twisting while allowing adjustment. To increase the tension on the band, traction is placed on the two cut ends of the band while a needle holder grasps the suture and allows it to slip. To decrease tension on the band, traction is placed on segments of the band on either side of the loop..
<3>Modification of routine buckling
The most common problem requiring a modification in technique is the presence of thin sclera (Figure 5-4). When this is encountered, scleral suture bites must be placed in positions that are less potentially hazardous. In most such situations, this can be accomplished with suture passes on either side of the ectatic sclera and/or with the use of a wider piece of silicone buckling material. More exotic means of managing thin sclera with donor sclera, tissue glue, etc, have been described, but pneumatic retinopexy with or without drainage of subretinal fluid or vitrectomy without scleral buckling are usually employed if scleral suturing appears to be impossible.
Rarely used today, intrascleral buckles involve lamellar dissection to create a partial thickness scleral bed. They usually involve only a limited part of the circumference of the globe, but can vary in length from one to twelve hours of the clock and in width from 4 to 12 mm. An encircling band is usually used, attached directly to the surface of the sclera in the areas not undermined, and the ends are joined together with only moderate tension. The implant is placed in the bed of the undermining, and the flaps are then closed over the top with sutures. This “trap-door procedure” creates a satisfactory buckle (Figure 5-10).
<2>Management of subretinal fluid
Decisions regarding the drainage of subretinal fluid are among the most difficult associated with scleral buckling procedures, and considerable differences in opinion exist. Drainage is almost never performed if responsible breaks can be easily and almost completely approximated to the pigment epithelium with a non-drainage technique. Drainage is almost always performed if a high and broad encircling scleral buckle is required. However, in most cases the criteria for drainage or non-drainage are less obvious. In eyes in which drainage was considered to be neither clearly unnecessary nor mandatory, a small randomized trial demonstrated comparable results with both techniques. In most cases, the decision regarding drainage depends upon the size and configuration of retinal tears, the amount of traction, the appearance after the scleral buckle has been elevated beneath the retinal break(s), and the experience of the surgeon regarding the amount of subretinal fluid that can be allowed to remain between the crest of the buckle and the break(s). Most non-drainage procedures are effective if the crest of the buckle is within 3 mm of the respective retinal break. Although this may be relatively easy to accomplish when buckling a single break, the need for more extensive buckling of multiple breaks makes this a more difficult goal and favors a drainage procedure. Because of complications associated with drainage of subretinal fluid, it is avoided unless considered to be necessary for surgical success. If failure to drain results in persistent subretinal fluid postoperatively, an intravitreal gas injection performed in the office can frequently cause the fluid to settle. Nevertheless, most surgeons perform trans-scleral drainage of subretinal fluid in approximately 75% of retinal detachment cases managed with scleral buckling. However, with increasing popularity of primary vitrectomy for retinal detachment, many surgeons now consider vitrectomy in cases that are likely to require drainage and use drainage in a smaller percentage of scleral buckle cases. Still, drainage and non-drainage techniques play a major role in the management of a routine series of cases, and familiarity with both techniques is essential.
The most common indication for a non-drainage technique is a retinal detachment due to a single break that can be approximated close to the pigment epithelium by scleral depression. Following the treatment of the break with cryotherapy and placement of appropriate sutures, the scleral buckle is elevated to the desired height, and the proximity of the retinal break to the surface of the buckle is re-evaluated. If the break is not perfectly positioned, the scleral buckle must be adjusted. The breadth of the buckling effect can be extended with additional sutures placed anterior or posterior to those already holding the buckle. If the posterior edge of the break is not positioned on the center of the buckle crest, at least one arm of the mattress suture must be repositioned. Assuring perfusion of the central retinal artery is critical if non-drainage techniques are employed. Unless fluid has been removed from the eye, placement of a scleral buckle will usually raise intraocular pressure so high that the central retinal artery is no longer perfused. This is temporarily tolerable but pressure must be lowered and perfusion restored approximately five minutes. Whether or not subretinal fluid is drained, pulsating perfusion of the central retinal artery must be confirmed by the end of the case. It can be difficult to determine if the central retinal artery is patent. If pulsations of the central retinal artery are observed following segmental buckling, perfusion is usually sufficient. If pulsations are not visualized and perfusion is questioned, additional digital pressure should be applied to the globe to elicit pulsations. If these do not occur, the arterial flow into the eye has probably ceased, and intraocular pressure must be reduced if pulsations do not begin soon. Intraocular pressure can be reduced by drainage of subretinal fluid, paracentesis, aspiration of fluid vitreous, and/or reduction in height or extent of the buckle. Paracentesis is usually performed in non-drainage procedures to achieve timely reduction of intraocular pressure after placement of the buckle, although this is usually not necessary if only a single radial buckle is placed. If repeated paracenteses cannot reduce intraocular pressure sufficient to reopen the central retinal artery, pressure can also be reduced by aspirating fluid from the posterior vitreous cavity. However, this maneuver is associated with many more potential complications than paracentesis. If optimal buckle size and suture width have been employed, the height of the buckle can be increased by further tightening of mattress sutures after intraocular pressure has returned to relatively normal levels. Sutures are initially tied temporarily to facilitate this adjustment. Perfusion or at least pulsation of the central retinal artery must be documented each time that sutures are tightened, and this is particularly important in eyes with reduced outflow facility.
Drainage of subretinal fluid is performed at a site determined by the configuration of the retinal detachment. Sufficient subretinal fluid is necessary to allows safe drainage. Factors considered in the selection of a drainage site include (1) the distribution of subretinal fluid when the eye is in a position at which drainage will be performed, (2) the location and size of the retinal break(s), (3) the location and configuration of the buckle, (4) the vascularity of the choroid, (5) features of vitreoretinal and epiretinal membrane traction, and (6) the ease of exposure of the proposed drainage site. The optimal locations for drainage are usually just above or below the lateral rectus muscle, because major choroidal vessels are avoided, and exposure of sclera is excellent. Choroidal vessels are also avoided by draining on either side of the three remaining rectus muscles, but exposure is frequently more difficult. If possible, drainage is usually performed some distance from retinal breaks, especially large retinal breaks, so that passage of vitreous through the break(s) and out of the eye can be minimized. The scleral depression effect provided by the buckle or by a cotton tipped applicator can help prevent this occurrence. In unusual situations in which a large buckling effect is required and very little subretinal fluid exists, drainage can be performed immediately beneath a large tear to allow both subretinal and intravitreal fluids to exit the globe. Drainage is performed prior to tightening the scleral buckling elements onto the eye, since a high intraocular pressure at the time of drainage increases the risk of complications. A site is usually selected at or slightly anterior to the equator, and a location that will ultimately be closed by the exoplant is preferred. This avoids the need for a preplaced suture at the sclerotomy site, and it facilitates subsequent management of drainage complications, as noted later. In the situation in which drainage cannot be performed optimally at a site intended to be covered by the buckle, a preplaced suture is employed to close the scleral incision following drainage. This suture is placed after the sclera incision is made but before the choroid is penetrated. A 3-4 mm radial incision through sclera is performed so that the center of the sclerotomy will be at the appropriate location. All scleral fibers are carefully divided until subtle prolapse of uveal tissue is observed (Figure 5-11). The choroid is then closely inspected for prominent choroidal vessels, using loupes and/or the 20 diopter condensing lens and indirect ophthalmoscope. If large visible vessels cannot be avoided during planned penetration, a second site nearby is selected, and another scleral incision is performed. If the area of exposed choroid is free of prominent vessels, it is usually treated lightly with a flat diathermy probe. This causes minimal retraction of the edges of the sclera to improve visualization, and it may reduce the risk of hemorrhage. All significant traction upon the eye is eliminated to reduce intraocular pressure as much as possible. The choroid is then penetrated with a sharp-tipped conical penetrating diathermy electrode or suture needle. Modest pressure is used to insert the device perpendicular to the surface of the sclera until the subretinal space is entered. If the conical diathermy electrode is used, this event is usually heralded by a sudden subtle "pop" which is usually perceived by touch or observation. Because of the tapered shape of the electrode, significant amounts of subretinal fluid do not exit the eye until this device is very slowly withdrawn from the eye. The penetrating diathermy electrode is relatively blunt, compared to a suture needle, and penetration of a soft eye with a congested choroid may be somewhat difficult. This is managed by modest elevation of intraocular pressure with traction upon the muscle fixation sutures. An oblique or tangential path of penetration is recommended by some authors to avoid perforating the retina, but this can result in a flap valve of the choroid, which can limit drainage. If a proper drainage site has been selected, penetration of the retina with the tapered diathermy is exceptionally rare, because it is removed prior to the release of significant amounts of subretinal fluid. Lasers have also been employed to drain subretinal fluid, but the expense and time required to use them do not appear to be balanced by a significant reduction in the rate of complications. As the globe softens during drainage, intraocular pressure is very slowly increased to encourage further drainage and to avoid complications associated with hypotony. If a large tear is present, the sclera or the buckle and sclera overlying the break are indented with a cotton applicator. This maintains intraocular pressure and inhibits passage of intravitreal fluid to the subretinal space. Pressure can also be increased by placing applicators on either side of the sclerotomy site and gently pushing them toward the center of the eye, and these maneuvers also tend to keep the sclerotomy open. Relatively normal intraocular pressure can also be maintained by indenting the sclera at a location far from the sclerotomy site with numbers of cotton applicators. The drainage site is not touched as long as fluid flows through it. Sudden and significant increases in intraocular pressure are avoided to reduce chances of incarceration of the retina in the sclerotomy, and any sudden cessation of drainage requires immediate closure of the sclerotomy and internal examination of the sclerotomy site with the indirect ophthalmoscope. The appearance of pigment granules suspended in the draining subretinal fluid usually indicates that the last of the subretinal fluid is exiting the eye. When drainage ceases, the sclerotomy site is closed by temporarily tying the sutures over an exoplant or by pulling together the ends of an encircling band. If the locations of buckling material will not adequately close the sclerotomy, the scleral incision is closed with the preplaced suture prior to significant elevation of intraocular pressure with the buckle. The eye is quickly inspected following closure of the sclerotomy site and a preliminary adjustment of the scleral buckle. The site of drainage is first evaluated for signs of subretinal bleeding, retinal incarceration, and iatrogenic hole formation, and management of these relatively unusual introperative problems is briefly discussed later. The amount of persistent subretinal fluid is then determined, and the need for further drainage is considered. Significant subretinal fluid is allowed to persist if the optimal amount of buckling nearly closes the retinal break(s). If drainage of additional subretinal fluid is required, the initial sclerotomy site must be closely evaluated with mobile scleral depression, in which a cotton-tipped applicator is rolled circumferentially beneath the area of drainage. If the pigment epithelium is clearly not in contact with the retina, the sclerotomy site can be reopened by reducing intraocular pressure and/or removing the portion of the exoplant that covers the scleral incision. Additional drainage usually occurs spontaneously, or it can be initiated by gently manipulating the edges of the sclerotomy with applicators or a forceps. In some cases, particularly those with exceptionally viscous subretinal fluid, the retina may flatten completely at the site of the sclerotomy while large amounts of subretinal fluid persist elsewhere. In this situation, additional sclerotomies must be performed if additional drainage is required to produce an adequate buckling effect. An alternative and increasingly popular method of draining subretinal fluid is to insert a small 25-27-gauge needle into the subretinal space using direct visualization with the indirect ophthalmoscope or operating microscope. The needle is usually attached to a tuberculin syringe from which the plunger has been removed (Figure 5-12). Digital pressure is exerted on the eye or significant intraocular pressure is maintained with traction sutures as the subretinal fluid passively exits the eye. The needle is dynamically positioned to remain within subretinal fluid, and it is slowly retracted as the retina approximates its tip.
<2>Adjustment of scleral buckle
Following drainage of appropriate amounts of subretinal fluid, an optimal scleral buckling effect is created by adjusting the scleral sutures and the length of the encircling band. Broad sutures over the portion of the buckle supporting large retinal breaks are first temporarily tied in a manner intended to provide optimal width and height. If intraocular pressure remains low and the breaks are in optimal position, the sutures are permanently tied. The height of the buckle is adjusted if it is inadequate or excessive. If a fold of retina continues to communicate with an open retinal break ("fish-mouth phenomenon") following buckle adjustment, a variety of manipulations can be used to solve the dilemma, as noted later. If an encircling band has been used in combination with a wider circumferential tire of hard silicone, its ends are overlapped to provide a modest buckling effect supporting the posterior edge of the vitreous base in areas not occupied by the tire. If the encircling band is used without a tire, it is adjusted to create an indentation of somewhat greater height. The degree to which the band should be tightened depends upon the intraocular pressure, the nature and extent of vitreoretinal pathology, and the necessity of a subsequent intravitreal gas injection. If the intraocular pressure remains quite soft following appropriate adjustment of the scleral buckle and retinal breaks are flat, balanced salt solution should be injected into the vitreous cavity via the pars plana. Attempts to restore normal pressure with further increases in buckle height can lead to a number of postoperative problems. Indications for gas injections are described below. The need to replace buckling materials or sutures is quite unusual if appropriate localization of retinal breaks has been performed. However, augmentation of the buckle in certain areas is frequently desired. This can be accomplished with suture adjustments if wide elements are already in place. If an encircling band has been used, and an augmentation of the buckle is needed in an area supported only by the band, hard silicone pieces of an appropriate size may be placed beneath the band, and these usually are not sutured.
Although scleral buckles are successful in producing a functional closure of retinal breaks in most cases, their effectiveness can be enhanced with accessory techniques, including intravitreal fluid and gas injections, gas-fluid exchanges, and postoperative laser photocoagulation. The first option, injection of balanced salt solution, is employed primarily to restore normal intraocular pressure to a hypotonous eye. Intravitreal gas injection and air fluid exchange are usually used to assist in the internal closure of retinal breaks. Laser photocagulation is usually not used at the time of scleral buckling but can be employed to create or augment a chorioretinal adhesion postoperatively.
<3>Intravitreal injection of balanced salt solution
The solution is drawn into a syringe, and all air is carefully eliminated. A 0.5-inch, 30-gauge disposable needle is recommended. As the surgeon grasps the sclera with a twist pick or forceps, the needle is introduced into the vitreous cavity 3mm (pseudophakic/aphakic eye) or 4 mm (phakic eye) posterior to the limbus. The tip of the needle is directed toward the geometric center of the globe. In a very soft eye, the tip of the needle may occasionally elevate the pars plana epithelium without perforation. Injection in that situation would produce detachment of the pars plana and retina. This can be avoided by direct visualization of the tip of the needle through the pupil and, when the needle is definitely within the vitreous cavity, the injection can be safely carried out. In phakic eyes, care must be taken to keep the tip of the needle near the middle of the vitreous cavity to avoid touching the lens and causing a subsequent cataract. After injection of the required volume to restore normal intraocular pressure, the needle is withdrawn. The self-sealing wound does not require suturing.
<3>Intravitreal gas injection.
Gas injections to internally tamponade retinal breaks are commonly performed in association with scleral buckling procedures. Gas is usually injected after the breaks have been treated and well positioned on the scleral buckle. The type and volume of injected gas depend upon the available potential space within the vitreous cavity as well as the size of retinal break(s) and the desired duration of tamponade. The injection technique is similar to that described in detail in Chapter 6. In the vast majority of cases in which the buckle is in appropriate position, an effective tamponade is necessary for only 24-48 hours. A 1.0 ml bubble of air is usually quite sufficient to tamponade a large retinal break, as a 0.30 ml bubble will maintain contact with a 90-degree arc of the retina. A 1.0 ml bubble of air is not absorbed for three to four days. However, injection of even 0.3 ml of gas into an eye with normal intraocular pressure will cause a marked increase in intraocular pressure and a transient occlusion of the central retinal artery. Therefore, the eye must be quite soft prior to an injection of a large gas bubble, or a smaller volume of an expansile gas is employed. In cases in which a longer tamponade effect is desired, more insoluble gases such as sulfur hexafluoride (SF6) and perfluoropropane (C3F8) are used. These possess two potentially favorable characteristics: expansile qualities if injected as pure gas, and longer duration in the eye. Numerous techniques of gas injection have been described. A simple method is to grasp a muscle insertion to fixate the eye and to penetrate the globe with a 30-gauge needle attached to a tuberculin or 3 ml syringe containing the desired amount and concentration of gas. The injection is performed 4mm posterior to the limbus in a phakic eye and 1mm closer to the limbus in an aphakic or psudophakic case. The site of injection is made uppermost so the bubble will tend to remain at the site of the needle tip, to avoid formation of multiple small bubbles. Using indirect ophthalmoscopy, passage of the needle tip through the pars plana epithelium may be confirmed. The needle is then withdrawn enough to leave about 3 mm of the needle in the eye. The predetermined volume of gas is injected moderately rapidly. The optic nerve is then inspected to document perfusion of the retinal vessels. If pulsations are visualized in a patient with normal blood pressure, no tension-lowering manipulations are performed. If pulsations are not observed and cannot be produced with digital pressure, the intraocular pressure is lowered with a paracentesis if pulsations have not resumed after several minutes. The height of the buckle can also be reduced or some of the gas can be removed if necessary to restore patency of the central retinal artery.
When a relatively large volume of gas is required, and intraocular pressure cannot be adequately lowered by any other means, fluid can be removed from the vitreous cavity prior to gas injection. This is commonly performed during vitreous surgery but rarely during routine scleral buckling operations. If a total posterior vitreous detachment has been documented preoperatively, and the retina is relatively flat, fluid can be aspirated from the space behind the posterior hyaloid with a 25-gauge needle inserted via the pars plana. It is helpful to have a very small volume of balanced salt solution in the syringe. When the needle is in place, 0.1-ml solution should be injected. This displaces vitreous gel at the tip of the needle and thereby facilitates the aspiration of fluid vitreous. Alternatively, a vitrectomy-cutting instrument can be used under indirect ophthalmoscopic control. This alternative has the advantage of reducing possible vitreoretinal traction but involves extra cost and time for setting up equipment. Gas is injected after the eye has been softened by either technique.
In cases in which cryotherapy can not be appropriately performed or excessive treatment is feared, retinal breaks can be treated with laser therapy after the retina is totally reattached with a scleral buckle. Some surgeons prefer this technique as a routine. However, a thin film of persistent subretinal fluid following routine drainage may result in excessive laser energy being required to produce a visible burn, and it may be easier to perform laser treatment a day or two following the primary procedure. In addition, in selected cases, recurrent retinal detachments following routine scleral buckling can be repaired by reattaching the retina with a gas bubble followed by later laser photocoagulation. <2>Closure of incisions
After placement and adjustment of the scleral buckle have been completed, any excess silicone or relatively sharp implant edges should be carefully trimmed, especially in very anterior buckles. Irrigation of the operative field with an antibiotic solution is usually performed, and this should be deep in the plane between Tenon’s capsule and the sclera in all opened quadrants. Peritomies are closed with interrupted or running sutures. Some postoperative suture discomfort can be eliminated by burying the suture knots in Tenon’s space.
Surgical follow up
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