Ординатура / Офтальмология / Английские материалы / Glaucoma Surgery_Trope_2005

bleb fibrosis and failure (2). Furthermore, it makes the patient feel uncomfortable and may predispose to infection.

4.2.3.Surgical Management

Signs of poor visual or bleb outcome require surgery, sooner rather than later. There are some absolute indications for surgery.

1.A flat AC with lenticulo-corneal touch is an emergency and should be operated on immediately. It can threaten vision from endothelial cells loss (direct trauma) and cause corneal decompensation. There can be .50% endothelial cell loss following lenticulo-corneal touch (11). Endothelial cell loss following iridocorneal touch is not usually clinically significant. A shallow AC does not influence the outcome of filtering surgery but a flat AC is associated strongly with bleb failure (2,12). Peripheral anterior synechiae can form and compromise the filtration procedure.

2.“Kissing” choroidal effusions threaten vision as they may result in retinal adhesion. Smaller choroidal effusions tend to resolve slowly when the factors that initiated their formation have been reversed; however, “kissing” choroidals may not and surgical attention is required. The only time “kissing” choroidals can be left is if the chamber is reformed and IOP has increased (either spontaneously or with surgery) and the “kissing” has been present for only 1 2 days and is noted to be resolving.

3.A shallow chamber present for .7 10 days with or without choroidals requires surgical reformation utilizing air, viscoelastic, or gas. We prefer not to drain choroidals unless they are “kissing.” If repeated AC reformation fails, we recommend draining choroidals with AC reformation. If that fails to resolve the over filtration, the wound will need to be resutured by opening the conjunctiva and placing additional sutures into the wound at the leaking areas (often found close to the limbus).

4.Relative indications for surgical intervention; these include a progressively shallowing AC, choroidal effusions close to touching, a hemorrhagic choroidal detachment that is suspected with low IOP because of inflammation, or a flattening bleb with signs of bleb failure. A filtration bleb requires some aqueous flow through the bleb for survival and prolonged hypotony with a flattening bleb is not a good prognostic sign, especially in combination, these may warrant surgical intervention.

5.SURGICAL TREATMENT OPTIONS

In cases of hypotony due to over filtration reforming the AC, draining the choroidal effusions and resuturing the scleral flap or a combination of these will resolve the situation.

5.1.AC Reformation

The best place to correct a flat AC is in an operating or treatment room, using an operating microscope for maximal control; reformation at the slit lamp is an option. The AC can be inflated with air, BSS, viscoelastics (of varying viscosities), or gas. Reforming the AC is a fast, less invasive, and often an effective way of treating flat or shallow AC and choroidal effusions. It is less traumatic than draining choroidal effusions; is associated with a lower

long-term IOP when compared with observation alone; is associated with fewer complications and with a better visual acuity outcome long-term when compared with choroidal drainage (6). This is the first option if the AC is flat (lenticulo-corneal touch), if the AC is shallow with corneal edema for .7 10 days, or if there is a progressive shallowing of the AC with signs of bleb failure.

For the procedure, topical anesthesia is usually sufficient. A sterile technique is mandatory and an antiseptic, such as povidone-iodine, should be used to disinfect the eye, even when this is performed at the slit lamp. A speculum is used to keep the eye open and then air, viscoelastic, or gas is injected via the temporal paracentesis. If access via the paracentesis is not possible then a 30 gage needle can be used to enter the AC. This may be technically challenging with a flat or very shallow AC. It is more hazardous in a phakic eye and must be performed using an operating microscope. Always ensure ocular stability by holding the eye with fine-toothed forceps preferably at the 3 or 9 o’clock position. Insert the needle starting 0.5 mm from the limbus under peripheral conjunctiva with the bevel facing towards the surgeon. On entering the AC the needle tip will touch the iris. As it does so, rotate the syringe 458 so that the bevel enters the AC. Inject and reform the AC at this time. Be very careful not to penetrate the iris and damage the lens. Remember touching the iris can be painful for the patient hence the need for firm ocular stability. Be very careful not to damage the bleb area while performing this maneuver.

Descemet’s membrane tear and detachment are possible complications of this procedure. This complication occurs if the needle is not fully in the AC before the viscoelastic is injected. A method to reduce this risk is by leaving some air in the needle (6). There is greater resistance to air injection if the needle is intracorneal and not intracameral. Take care; with a sufficient push, air can be injected into the cornea causing disruption to the lamellae producing a transient “shattered glass” appearance. This appearance, however, has minimal long-term consequences.

In only reforming the AC, air, gas, or viscoelastic can be used; fast redistribution means that BSS will not alone maintain the AC. Any of these three may alter the hypotony-choroidal effusion vicious cycle; with a formed AC and increased IOP the choroidal effusions absorb. Longer lasting gases, such as sulfur hexafluoride (SF6) and perfluoropropane (C3F8), have been advocated (13,14). Air and gas do cause some endothelial cell loss and cataract in rabbits and humans (15,16); viscoelastics have a wider safety margin for corneal endothelium and the lens. Sodium hyaluronate (Healonw) does not maintain the AC for very long, usually only a day or so (Table 25.1) (17). The most appealing viscoelastic is Healonw5; this is cohesive in low shear situations and fractures into smaller fragments with higher flow rates (18,19). One of us (Trope G) finds air most useful in these cases.

On injecting gas or air, if the patient is phakic, dilating the pupil may increase the lens gas contact area and thus the potential for cataract formation (14). Cycloplegia, however, is an important part of the management. In some cases, gases may be successful where air and viscoelastics have failed (13). Usually an isovolumetric, nonexpansile mixture of air and gas is used (mixed with air so that the bubble does not increase in size), for example, 40 50% SF6 and 12 15% C3F8. When these concentrations are used, the detrimental effect to corneal endothelium is equivalent to air alone. Success has been reported with 20 40% SF6 with minimal effect on the lens and cornea (20). A recent report of two cases used a combination of 100% SF6 and Healon with success (21). If using air or viscoelastic, the AC should be fully inflated or hyper-inflated taking care not to raise the IOP excessively. If using gas in nonexpansile concentrations, the AC can be filled and the size of the bubble is limited by the size of the AC ( 0.2 mL) (14). However, caution must be exercised if higher concentrations are to be used; 100%

C3F8 will quadruple in size over several days and could potentially cause very high IOP. The advantages and disadvantages of each substance are outlined in the Table 25.1.

5.2.Drainage of Choroidal Effusions

The second operative option is draining the choroidal effusions via a sclerotomy. Draining the choroidal effusions and reforming the AC reverses both the pathologies present. It is mandatory if the choroidal detachments are “kissing,” if the effusions are touching the posterior surface of the lens, or when AC reformation alone fails to restore the AC and bleb function and there is a significant effusion present.

Drainage of choroidal effusions should only be performed in an operating room. Often a corneal stay suture is not necessary. Reform the AC with BSS or viscoelastic through the operative paracentesis (or a newly created one). Make a circumferential infero-temporal and/or infero-nasal conjunctival incision 3 5 mm from the limbus. Create a 2 4 mm long horizontal sclerotomy with #11 Bard-Parker blade (or similar) centered 3.5 mm from the limbus over the pars plana [Fig. 25.2(a)]. Using diathermy if needed, gently cut down till the supra-choroidal space is entered. The sclerotomy can be extended to create two full thickness cuts meeting at an angle (in the shape of an “L” or “T”). A spatula can be introduced between the pars plana and sclera [Fig. 25.2(a)]. Drain supra-choroidal fluid and reform the AC with BSS or viscoelastic. Repeat this process until no further fluid can be drained. You can encourage more fluid drainage with gentle pressure on the globe with a cotton bud alongside the sclerotomy or by reforming the AC while lifting the lips of the sclerotomy [Fig. 25.2(b)]. Drainage can take time. To document a cyclodialysis cleft, dilute 2% fluorescein with BSS and inject it into the AC to see if it passes through the sclerotomy (22). As supra-choroidal fluid is light yellow in color, recognizing the fluorescein may be challenging. Suspect a cleft if the AC fails to remain formed. Examine the posterior segment with an indirect ophthalmoscope to document shrinkage of the effusions. Leave the sclerotomy open and close the conjunctiva with a Vicryl suture. Preferably use a viscoelastic to reform the AC at the end of the procedure. Choroidal effusion drainage is associated with a worse outcome for

Figure 25.2 Posterior sclerotomy: (From Maurice H Luntz and Raymond Harrison. Glaucoma Surgery, 2nd ed). (a) Scleral incision and introducing a flat spatula and (b) draining fluid.

visual acuity (6). Possible complications include infection, inflammation, and suprachoroidal hemorrhage (22).

5.3.Scleral Flap Repair

This involves re-opening the drainage bleb. This is done in the operating room under topical or sub-Tenon’s anesthesia. The sutures are then removed from the conjunctival wound and the wound edges gently opened. Be prepared to deal with some bleeding but use cautery sparingly so as not to damage the conjunctiva.

To repair the scleral flap, place 10/0 nylon sutures across the leaking areas. These are often found close to the limbus. If this is not possible (e.g., scleral thinning or dehiscence), a scleral patch graft may be necessary. Be prepared for this possibility. To close the conjunctiva effectively, resection of thin, ischemic leaking tissue may be necessary to close the defect. A conjunctival (advancement pedicle or sliding) flap or an autograft from the inferior conjunctiva or the other eye may be necessary. Suturing down the flap with AC reformation and choroidal drainage definitively raises the IOP and reverses the cycle of hypotony and choroidal effusion. However, because the conjunctiva is disturbed at the fistula site, there is a significant risk of bleb fibrosis and failure.

6.CONCLUSIONS

The timing of surgical treatment for shallow or flat AC, with or without choroidal detachment, depends on early recognition and diagnosis of vision threatening or bleb threatening complications. Corneal decompensation, retinal adhesion, and fixed chorioretinal folds are likely causes of permanent vision loss. In addition, bleb function may be compromised by periods of hypotony. Milder degrees of choroidal effusion and shallow AC usually resolve with time and without surgical intervention. Among interventions, AC reformation yields the best visual and IOP outcomes for shallow or flat chambers and should be used as the first invasive step; air, viscoelastics, and gases can be used and choice of substance depends on surgeon preference and availability. If this fails, choroidal effusion drainage with or without scleral flap repair should be considered.

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Figure 26.1 (See color insert) Fundus photograph detailing choroidal folds.

2.CAUSE(S)

The usual causes of hypotony are overfiltration, or a leaking filtration bleb in the postoperative period. Hypotony from aqueous shutdown is rare (2), although ciliary body toxicity from mitomycin C application has been reported (8). Other causes such as severe coughing, argon laser suture lysis, especially if a bleb leak was produced, or even argon laser trabeculoplasty have been reported (1,9 14). The incidence of hypotony following argon laser suture lysis has been reported in 21% (12), but resolved with conservative management in 12 of the 13 patients affected. The authors noted a decreased risk of hypotony when the suture lysis was delayed after the surgery. The usual recommendation is to wait at least a week before performing argon laser suture lysis if antimetabolites, particularly mitomycin C, have been used in order to prevent hypotony in the early postoperative period (15,16). However, this is not always practical with lysis often performed from day 2 onwards (17). Another condition that may, rarely, predispose to hypotony maculopathy is pseudotumor cerebri. One report has suggested that an imbalance between low IOP following trabeculectomy and raised intracranial pressure may result in a translaminar pressure differential that results in optic disc swelling as well as macular changes (18). The underlying reason why some patients with hypotony develop maculopathy and others do not remains unclear, although it is suspected that varying degrees of scleral rigidity may contribute, with patients having less scleral rigidity being more predisposed to maculopathy. Similarly, the presence of a choroidal effusion has been reported to be associated with lower risk of macular changes (19).

3.DIAGNOSIS

Hypotony maculopathy is diagnosed clinically and with the aid of intravenous fluorescein angiography. Gass (5) published an early description of hypotony maculopathy, and was the first to use the term, although he stated that it could more accurately be called “hypotony chorioretinopathy,” as the entire fundus is affected. Gass described choroidal folds radiating away from the fovea, most marked nasal to the optic disc, with overlying retinal folds (Fig. 26.2). There may be elevation of the optic disc margin. Findings seen