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

The surgeon makes temporary marks on the sclera with a scleral marker like the O’Connor marker or a Gass thimble. Finally, the surgeon enhances these marks with a marking pen, superficial cautery, or both.

The location marks depend on the characteristics of the breaks. For these cases the surgeon marks the posterior edge of small breaks and both ends of lattice degeneration whenever present (Figure 7). In cases in which a dialysis type tear is present, one should mark both edges, as well as the posterior extent to which the retina is likely to fall in a posterior direction (Figure 7). In large horseshoe tears, the posterior edge and both anterior horns are marked. Precise anterior and posterior localization of large horseshoe tears is very important since many of these tears are not radially oriented (Figure 7).

The surgical microscope may be used for external dissection. This is particularly important in re-operations and during the fluid drainage process. Using the microscope gives the surgeon greater control, illumination, and better visualization of tissue details. Although the surgeon also may use the surgical microscope for intraocular visualization during pars plana vitreous surgery, it is important to use the indirect ophthalmoscope (Figure 8), during buckling surgery for primary retinal detachments.

Figure 7: Localization Marks Depending on Retinal Tear Characteristics. In this series of figures, the dotted lines show the internal boundaries of the various types of retinal tears. The black dots show the proper location of the external scleral marks which are made to denote the boundaries of each. 1.) In the case

eration are marked on the sclera. 3.) The boundaries of a dialysis are noted by marking both ends and the posterior extent to which the retina will likely fall. 4.) For large horseshoe tears (Fig. 9 top), the posterior edge and the ends of the anterior flaps are marked externally on the sclera. 5.) Because such large tears may not be radially oriented as shown, it is important

localization of lesions and precise buckling implant procedure for a primary retinal detachments surgery. Please observe how the multicoat 20D lens is managed during the process of drawing the lesions implicated in the retinal detachment. (Art from Jaypee Highlights Medical Publisher).

After locating and marking the retinal tears, the surgeon must decide whether to use a localized exoplant and, if so, whether it should be radial or circumferential (see Figure 10 for a circumferential localized exoplant). He also chooses whether to use an encircling element alone or a combination of a radial and an encircling element (Figure 9). The type of material must also be selected.

Exoplants

Exoplants come in two basic types: silicone sponges, and solid silicone rubber, both of which may also vary in shapes and sizes (Figure 10). Solid silicone rubber is available in bands, straight strips, and symmetric and

Figure 9: Combination of Radial and Circumferential Exoplant Resulting in Excellent Tissue Re-Apposition. The surgeon has decided to make a buckle using a combination of radial (R) and circumferential (C) exoplants, as shown in the lower part of this figure. The position of a retinal tear and hole beneath these exoplants is shown as a dotted line. The tissue apposition internally is perfect as revealed by the path of the slit beam in the top figure. (Art from Jaypee Highlights Medical Publisher).

asymmetric tires. Some solid elements can be placed radially. Silicone sponges are either cylindrical in shape, 3 mm to 5 mm in diameter, or oblong with dimensions of 5 mm by 7 mm. Some sponges are grooved, with a channel in the middle. They are designed to be used in conjunction with an encircling silicone band. Segments of cylindrical sponges can be placed radially or circumferentially.

Figure 10: Different Types of Exoplants. Exoplants come in two basic types: silicone sponges and solid silicone rubber. Samples of each are shown in place on the globe and in cross section. As shown in figure above, solid silicone rubber is available in bands (A) both wide and thin (H), in straight strips (B), asymmetric (C) and symmetric (D) tires. Silicone sponges are shown below, as follows: cylindrical (E), or oblong (F). Sponges can be grooved (G) for placement beneath a band (H). Segments of sponges can be placed circumferentially (G) or radially (I). (Art from Jaypee Highlights Medical Publisher).

Selecting the Exoplant

The best exoplant to use depends upon the characteristics and the extension of the retinal pathology, the volume of subretinal fluid, and the amount of vitreous traction. The surgeon may choose an encircling exoplant in the following types of cases: retinal detachments with multiple breaks, aphakic or pseudophakic eyes, the presence of high myopia, extensive areas of lattice degeneration, PVR grade B or greater, giant tears, and eyes with very thin sclera. The surgeon may choose one or more from a great variety of elements, such as 41 or a 240 band combined with a grooved silicone strip or tire in most cases; occasionally, he will combine a 240 band with a grooved 6.5 mm sponge, in which case its circumferential length depends upon the extent of the retinal pathology (Figure 11).

Segmental circumferential buckles are indicated in closely spaced retinal breaks in the absence of other retinal pathology. Radial exoplants are preferred in cases with large horseshoe tears and relatively posterior tears. In our practice, with most horseshoes tears, we usually prefer a 4- or 5-mm silicone sponge cut in half, lengthwise, along the longitudinal axis of the tear. In cases in which the retinal pathology compromises more than one quadrant, and particularly, if it is associated with mild vitreous traction, one should consider using an encircling 240 solid silicone band (Figure 11).

Figure 11: Indications for Radial Exoplant and Encircling 240 Degrees Solid Silicone Band. Figure A shows a large, relatively posterior horseshoe tear (L) and two small closely spaced equatorial tears (S). Figure B shows the radially placed silicone sponge (M). The interrupted lines in the area of the sponge (L) represent the location of the horseshoe tear beneath the exoplant. The radial sponge exoplant is shown combined with the encircling 240 degree solid silicone band (E). On the area of the encircling band, to the right, the interrupted lines in the shape of a V but marked (S) represent the location of the two small tears beneath the band. Figure C demonstrates the internal view of (B) showing reattachment of the retina and the appearance of the tears on the buckles with excellent apposition of tissues once the operation is completed. (Art from Jaypee Highlights Medical Publisher).

Sutures and Securing the

Exoplant

The next step is the placement of the sutures to hold the exoplant in place to achieve an adequate indentation of the eye wall. Sutures of 5-0 polyester or nylon are placed with a half-curved spatula needle. The sutures should be inserted at approximately half the thickness of the sclera, and the suture bite into the sclera should be 3 mm to 4 mm in length. Suture placement depends upon the buckle being equatorial or radial. With a large, radially-oriented horseshoe tear (Figure 12), the distance between the marks at the anterior part of the tear is measured. This distance is extended by 3 to 4 mm. Sutures are then placed at these points. If the previous steps, have been performed properly, the tear should lie equidistant from the arms of the sutures. The sutures need to be 2 mm in front of the anterior marks and 2 mm posterior to the posterior marks in order to ensure a safe and efficient indentation of the sclera totally covering the tear (Figure 12).

For circumferential and encircling buckles, the goal is to have the tear, or the anterior and posterior marks of the tear, on the anterior slope of the indentation created by the buckle. This means that the distance between the suture bites must be twice as long as the distance between the anterior and the posterior marks of the tears. The tears have to be in the more peripheral half between these two points (Figure 13).

Figure 12: Suture Placement Technique for Radially Placed Exoplants. This conceptual illustration shows a section of the sclera with the proper placement of a radially placed sponge exoplant and a mirror view of the tear, detachment and ora serrata. Above, the foreground view (2) shows the external configuration of the exoplant (E) on the sclera (S) before tightening of the sutures. The image in the mirror (1-M) shows the corresponding internal configuration of the retinal detachment (R), retinal tear (T) and ora serrata (O). Note that the exoplant is centered over the retinal tear (2-dotted lines). The sutures are placed about 2mm anterior (A) to the anterior marks of the tear and also 2mm posterior (B) to the posterior marks. Laterally, the sutures are placed 2mm beyond (C) the anterior scleral marks. Overall, the tear should be between and equidistant from the arms of the suture.

Below, after tightening of the sutures (4), please observe the sponge exoplant (E) depressing the sclera externally in the foreground view. In the mirror view (3-M) showing the internal configuration, one can see the effect of this depression as the retina (R) is now reattached and the tear (T) is closed, flat and centered on the internally raised area (compare with (1)). (Art from Jaypee Highlights Medical Publisher).

Figure 13: Suture Placement Technique for Circumferential and Encircling Buckles. This conceptual illustration shows a section of the sclera with the proper placement of an encircling sponge type buckle. Above, the foreground view (2) shows the external configuration of the buckle

(E) on the sclera (S) before tightening of the sutures. The image in the mirror (1-M) shows the corresponding internal configuration of the retinal detachment (R), retinal tear (T) and ora serrata (O). Note that the sponge is located slightly posterior to the tear, and its anterior and posterior marks. The sutures are placed such that the suture bites are twice as long (D”) as the distance between the anterior and posterior marks of the tear (D’); the tear should be in the anterior half between the suture bites.

Below: following tightening of the encircling buckle sutures, notice the buckle (E) depressing the sclera (S) externally in the foreground view (4). In the mirror view (3-M) showing the internal configuration, one can see the effect of this depression as the retina (R) is now reattached and the tear (T) is closed and flat (compare with (1) above. Note that the tear is properly located on the anterior slope of the invagination. (This same configuration would hold true in the case of a circumferential solid silicone element (not shown), with the sutures placed in general 2mm further apart than the width of a given element, which fully encompass the retinal tear.) (Art from Jaypee Highlights Medical Publisher).

In general, when solid silicone elements are used, sutures are placed 2 mm further apart than the width of a given element. When cylindrical sponges are used, sutures are placed 2 1/2 mm to 3 mm outside the diameter of the sponge. In other quadrants where retinal pathology is not present, the band or the encircling element is placed about 3 mm to 4 mm behind the ora serrata. The scleral buckle is placed loosely to avoid any elevation of intraocular pressure.

Sealing the Retina

The next step involves inducing an adhesive chorioretinal irritation in order to create the scar that will seal the retina. The use of cryotherapy or diathermy has created some controversy in the past. While some reports have suggested that cryotherapy may cause pigment dispersion, which can in theory, lead to PVR, no clinical studies have confirmed this statement. Most problems with this method are caused by overdosing. The surgeons must indent only with the tip of the cryo-probe and not with the shaft to avoid inadvertent posterior freezes. The application of the first freeze to the most anterior aspect of the area of treatment so as to access both location and intensity of cryotherapy, is also recommended.

Some surgeons use diathermy, which requires scleral dissection in order to apply the thermal treatment in a controlled manner and without any scleral damage. It is important to understand that the surgeon’s preferred treatment modality will depend upon the type of training he has received.

Under indirect ophthalmoscopic visualization (Figure 6), we prefer the use the cryoprobe to depress the sclera precisely on the area of the retinal tear. With a small break, the cryoprobe should be depressed precisely at the break, and with a large break it should be depressed at the edges. The retinal pathology must be surrounded by cryoapplications. When treating horseshoe tears, the surgeon must reach the ora serrata from either side of the tear to prevent a recurrence of retinal detachment. Treatment should be applied just long enough for the color of the choroid to begin to change to white. Allowing ice crystals to form is an over application of the treatment, which can lead to pigment dispersion.

Laser treatment with argon or a diode laser attached to an indirect ophthalmoscope has become an alternative to cryotherapy or diathermy. The sclera is depressed in the area of the retinal tear, displacing the subretinal fluid and at the same time bringing the pigment epithelium in contact with the neuroretina (Figure 14). This facilitates a positive reaction that involves both the pigment epithelium and the retina.

While we use cryotherapy in most cases, others prefer the diode laser for an adequate and more gracious way to treat some retinal tears during primary retinal detachment surgery. Laser is an alternative for treating patients with clear media, where there is good visualization of the retinal tear. Patients with some degree of opacification of the lens (or of the capsule if they are pseudophakic) are better candidates for cryotherapy. A probe for transscleral diode laser application is another modality.

Figure 14: Laser Attached to Indirect Ophthalmoscope Treating and Sealing the Tear. Today there is another alternative to cryotherapy or diathermy: laser treatment with the argon or the diode laser attached to an indirect ophthalmoscope. In this internal/external conceptual view, a section of sclera (S) is shown removed to reveal a cross section during scleral depression (arrow) with an applicator (A) and laser application (L). With corresponding visualization through the indirect ophthalmoscope (O), the scleral invagination is seen in the area of the retinal tear (T). This scleral depression displaces the subretinal fluid and at the same time brings the pigment epithelium in contact with the neuroepithelium during application of the laser

(L). This facilitates a good reaction that involves both the pigment epithelium and the retina. Note existing circumferential exoplant (E). (Art from Jaypee Highlights Medical Publisher).

Draining the Subretinal Fluid

After the retina is sealed, the next step is the drainage of the subretinal fluid. This procedure enables the surgeon to decrease the intraocular volume, settle the retinal breaks on the buckle, and obtain a deeper indentation of the sclera to counteract the vitreous traction. Draining of subretinal fluid is recommended in: highly myopic detachments, aphakic and pseudophakic eyes, bullous detachments, multiple breaks, significant vitreous traction, giant tears, inferior breaks, and thin scleras.

The first step in draining the subretinal fluid, using indirect ophthalmoscopic visualization, is to select an area with an adequate amount of fluid to avoid damage to the retina. An area, in which preretinal membranes are present, is preferable because a stiff retina is less likely to be incarcerated. If possible, the surgeon should drain just above or just below the horizontal rectus in order to decrease the risk of bleeding. It is better to drain from the nasal side because, if bleeding occurs, there is less chance the blood will run under the macular area. When subretinal fluid does not reach the horizontal meridians, draining must be done elsewhere; either side of the vertical rectus muscle is another possible site.

Surgical Technique for Sclerotomy

After the drainage site has been chosen, a 3 mm to 4 mm sclerotomy is made with a 64 Beaver blade, under microscopic visualization. The sclera is incised until the choroid is

visualized (Figure 15). Mild cautery applications to the scleral edges cause some gaping of the wound to allow better visualization of the choroid. A mattress 5-0 polyester suture through the right lip of the sclerotomy is placed and gently pulled by the assistant to keep the wound open while the surgeon pulls on the other lip using a 0.3 mm toothed forceps (Figure 16). The illumination and the magnification of the microscope allow the surgeon to avoid the choroidal vessels and to apply exact diathermy touches, using the probe designed for intraocular applications if needed. At this point all external pressure must be avoided.

Then, using a sharp 27 half-inch bent needle, posteriorly oriented to avoid damage to the overlying retina, the surgeon stabs the choroid just enough to enter the subretinal space (Figure 17). The needle is then quickly removed, and the fluid begins to drain (Figure 18). The loss of volume and pressure might be compensated by slightly indenting the eye with cotton tip applicators, which are placed between the globe and the periorbital tissue, away from the drainage site. If the fluid suddenly stops draining, the fundus must again be inspected with the indirect ophthalmoscope before any additional maneuver is attempted. Some pigment granules might be seen in the subretinal fluid

Figure 15: Drainage of Fluid - Surgical Technique for Sclerotomy - Stage 1 - Incision. After the drainage site has been selected, under microscopic visualization, a 3mm to 4mm sclerotomy is made with a 64 Beaver blade (K). The sclera (S) is incised down until the choroid (C) is visualized. (Art from Jaypee Highlights Medical Publisher).

Figure 17: Drainage of Fluid - Surgical Technique for Sclerotomy - Stage 3 - Stabbing the Choroid. Using a sharp 27 half inch bent needle (N), posteriorly oriented to avoid damage to the overlying retina, the surgeon stabs the choroid (C) just enough to enter the subretinal space. The needle is then quickly removed. (Art from Jaypee Highlights Medical Publisher).

Figure 18: Sclerotomy Technique - Fluid Actually Draining. When the needle is removed, fluid begins to drain as shown. If the fluid ceases to drain, the fundus must be examined with the indirect ophthalmoscope. Some pigment granules (P) may be seen in the subretinal fluid when the drainage is almost complete. (Art from Jaypee Highlights Medical Publisher).

when the drainage is almost complete. The ocular fundus is once again inspected with the indirect ophthalmoscope to evaluate the amount of residual fluid and the position of the tears. It is rarely necessary to drain all subretinal fluid, as long as the buckle is adequate in size and position.

Closing the Scleral Wound

The scleral wound is prepared with a preplaced suture, which prevents certain types of complications (Figure 19). The scleral buckle sutures are then tightened, beginning at the area of the breaks, and moving to the other quadrants. If the eye is too soft, filtered air is injected through the pars plana to restore its volume. An air bubble, or a mixture of air and a perfluor-carbonaded gas, also helps to flatten the retina if a fish mouth effect to the retinal tear is present. This fish mouth type of gaping can be induced by relative circumferential shortening of the retina, which causes radial retinal folds to form over the buckle. The suture ends are adjusted enough to obtain the desired indentation effect to close the tears. They are secured with a silicon sleeve, a tantalium clip, or a nonabsorbable suture. When a 4 mm cylindrical sponge is used, a 5-0 polyester suture will secure it from end to end. The fundus is re-examined to evaluate the scleral indentation and the position of the breaks as well as to assure optic nerve perfusion (Figure 20). Tenon’s capsule is secured to the sclera next to the insertion of the rectus muscles in each quadrant to prevent any future extrusion of the exoplant. If the exoplant is not

Figure 19: Sclerotomy Technique - Final Stage - Closing the Wound. The wound is closed with the pre-placed suture as shown. The scleral buckle is tightened. (Art from Jaypee Highlights Medical Publisher).

totally covered with Tenon’s capsule, the risk of subsequent erosion and extrusion of the exoplant is increased.

After Tenon’s layer is closed satisfactorily, the conjunctiva is pulled anteriorly, and the radial cuts are closed with polyglycolic acid sutures, an antibiotic and a corticosteroid are applied topically.

Anatomical and Visual Result after Scleral Buckling

The overall rate of anatomical reattachment with current techniques is 90%. Aphakic and pseudophakic eyes have a slightly less favorable prognosis. Whether the macula was detached and for how long is the primary

Figure 20: Final View of Buckle with Retinal Indentation and Sealing. This internal/external conceptual illustration shows a cross section and corresponding surgeon’s view of the final configuration of a circumferentially placed sponge exoplant (E). The cross section shows a portion of sclera (S) removed for clarity. The surgeon’s view is through the indirect ophthalmoscope

(O). Note the indented configuration in both views. The retina is reattached and the tear (T) is flat. Also note that the tear is properly positioned on the anterior slope of the invagination. (Art from Jaypee Highlights Medical Publisher).