During the follow-up visit, gonioscopy, visual acuity examination, intraocular pressure (IOP), and postoperative complication were recorded, and the medication regimen was adjusted by the treating physician.
Primary outcome measures included a drop in IOP and improvement in visual acuity and also the extent of PAS.
Twelve patients were included in this study, including 2 men and 10 women. Mean patient age was 64.33±13.26 years (range: 37 to 78 y), and the underlying mechanism of angle closure included pupillary block (n=12). Two eyes had acute ACG related to enlarged or dislocated lens. Mean time of follow-up was 7.4 months, with a standard deviation of 1.4 months and the range was 6 to 10 months. Table 1 details further patient characteristics. Gonioscopy (before the surgery) or endoscopy (during the surgery) revealed 12 of 12 patients presenting with PAS ranging from 30 to 360 degrees before EGSL.
In the procedure of GSL, the view of the chamber angle was clear (Fig. 2A). All PAS were eliminated and ciliary body band became completely visible in all eyes (Fig. 2B).
Minimal hyphema occurred in 1 patient. No significant intraoperative complications, such as iridodialysis, occurred in any patient. Clear and convenient direct visualization provided a potentially precise and safe manipulation during synechialysis.
For patient outcomes, please refer to Table 1. The absolute success rate (IOP <21 mm Hg without medication) was 8 of 10. IOP was finally controlled under 21 mm Hg in the 12 eyes of 12 patients with no medication. At the final examination, IOP and the extent of PAS significantly decreased.
Visual acuity improved in 11 of 12 patients (91.7%). Few postoperative complications were noted in this series. Several patients (n=3) were noted to develop significant stromal edema of the cornea, which subsided with conservative therapy within 1 month postoperatively; 3 patients exhibited fibrin exudation. For most cases, EGSL was performed shortly after an acute angle closure attack or occurrence of flat anterior chamber. Finally, 2 patients who underwent EGSL with 360-degree PAS before surgery presented with a newly closed angle a few days postoperatively, and their IOP could not be controlled. These 2 patients were subsequently treated with trabeculectomy and the IOP was controlled at the last follow-up.
Recently, GSL with or without lens extraction and posterior chamber IOL implantation has been shown in different populations to be a good surgical option in the management of ACG.2–6 However, direct visualization of the chamber angle is one of the difficult procedures during GSL using conventional gonioscopic prism lens. Because the angle between the patient's and the surgeon's ocular axes must be at least 30 degrees, it requires tilting of the operating microscope, eyeball rotation with bridle sutures to enhance observation of the superior and inferior chamber angle, and adjustment of patient's head position to visualize the nasal and temporal angle areas during the operation. The plane of the trabecular meshwork is severely oblique to the surgeon's visual axis. The focus points between Schwalbe line and the iris recess differ under high magnification. These limitations reduce the quality of the images of the chamber angle and make the procedures hard to manipulate. Moreover, corneal opacity is also a major problem. Corneal edema or opacification renders gonioscopic observation of the chamber angle difficult, even impossible. Removing the opaque corneal epithelium does not always improve visibility. As a consequence, GSL surgery may not be possible. In the past few years, however, new slimmer fiber optic and even current-coupled device-based probes for microendoscopy have become available.24–26 Although the size of the instruments has been decreasing, the resolving power and image quality of the new generation microendoscopes have considerably improved. Consequently, the evolving potential of this fast developing technology has been appreciated in intraocular surgery. Currently, ophthalmic microendoscopes have been used successfully to illuminate and view the internal ocular structures clearly in complicated pars plana vitrectomy,12,27 transscleral IOL fixation,28 and ab interno glaucoma surgery.16–23 In this paper, the author managed to take advantage of microendoscopy to obtain an optimized visualization for the anterior chamber angle conveniently when performing GSL procedures.
Intraocular microendoscopy renders the anterior chamber structures visible to the surgeon irrespective of the media. As a result, EGSL could be performed easily regardless of corneal conditions. This gives the surgeons a better option when performing the operation. For example, in this paper, there are 2 cases of acute ACG related to enlarged or dislocated lens, where preoperative or intraoperative gonioscopy is infeasible because of cornea edema and opacities. However, with microendoscopy, the AS and the range of PAS could be viewed clearly during the surgery regardless of corneal opacity. It may conduce to make a better option, namely phacoemulsification-GSL or phacoemulsification-trabeculectomy.
Intraocular microendoscopy offers 5 other advantages:
- Tilting the operating microscope is not necessary, which aids surgical manipulation.
- The patient's head remains upright during surgery because head repositioning has been eliminated.
- The operating procedure is less invasive because no bridle sutures are needed.
- Compared with the conventional visualization system that uses surgical loupes, surgeons can obtain a greater magnified view of the AS by using an intraocular microendoscopy. A highly magnified image of the AS allows us to safely perform intracameral surgical procedures.8
- Surgical manipulation is much more convenient because there is no contact lens on the cornea during the operation. Consequently, manipulation could be more accurate and less harmful to patients.
Intraocular microendoscopy, however, has some drawbacks. First, the technique does demand some adaptation on the part of the surgeon because video monitor control, nonstereoscopic viewing, and sometimes single instrument intraocular manipulation all demand technical adaptation with a steep learning curve. Second, there exist substantial complications related to the endoscopy itself. Gayton29 reported that an iris adhesion to the endoprobe led to total aniridia in 1 patient undergoing laser. Third, EGSL may require 2 surgical incisions, 1 incision for endoscope into the anterior chamber, another for equipment access. If GSL is combined with phacoemulsification, no additional surgical incision or lengthened incision is required. The shortcoming mentioned above could be avoided.
Other visualization techniques also proposed using an indirect mirror gonioscopic lens1 and a double-mirror gonioscopic lens30 or double-mirror goniolens with dual viewing system.31 These methods are advantageous because they provide an upright image of the AS without tilting the patient's head and/or the microscope during the surgery. However, all the above techniques proposed using gonioscopic lens on the surface of the cornea during the operation. It is not convenient to manipulate and the corneal opacity might preclude AS viewing. Moreover, the disadvantages associated with the first lens include, the angle view is reversed, and the light reflected from its surface makes the view less optimal.8 The drawbacks of the latter include the reflection from the lens surface and the small area of interest that can be viewed.
Clinical data in the present preliminary series demonstrated that EGSL was effective for the management of synechial ACG. The reduction of IOP was similar to that in the previous studies.2–4 The recurrence of PAS was quite limited in our cases.
GSL is effective in lowering IOP in (Oriental) eyes with ACG and PAS.3 Lens extraction or phacoemulsification, even in eyes with good visual acuity, may open the angle and normalize the IOP.32,33 GSL is even more effective when combined with extracapsular cataract extraction. To avoid potential postoperative problems associated with the lens, combined GSL and lens extraction has been advocated.4,34 As lens extraction gives more room in the anterior chamber for EGSL, EGSL is also easier to manipulate. As discussed above, it is possible to presume that EGSL in aphakia eyes or combined with lens extraction is much more safe and effective.
The site of clear cornea or sclera tunnel incision of cataract surgery is determined according to the position of angle synechiae. As superior and nasal angle adhesion appears more frequently in ACG, a clear-cornea incision is usually made in temporal, superior temporal, or inferior temporal quadrant. Meanwhile, the site of side puncture in cornea can be determined accordingly.
Complete synechialysis may potentially prevent the recurrence of PAS and IOP increase because it could open the whole angle, rebuild the normal structure of the anterior chamber, and possibly restore trabecular function and aqueous humor outflow. We also found out that GSL via endoscopy combined with phacoemulsification and lens implantation was very safe and simple. As a result, we performed this procedure when the circumferential extent of PAS is 90 degrees or less.
Though the IOP is apparently already well controlled in 2 patients with flat anterior chamber after trabeculectomy, filtration failure may occur over time because of scarring of the filtering bleb. Performing GSL for PAS, which were sequelae of flat anterior chamber after trabeculectomy when the IOP is apparently already well controlled, will exhibit its effect. This is because GSL could open the angle, may restore trabecular function, and improve aqueous humor outflow to prevent the recurrence of IOP increase even after the blebs are encapsulated. In addition, GSL in patients with flat anterior chamber after trabeculectomy may decrease the inflammatory reaction and become helpful to the reformation of the anterior chamber. Moreover, we believed that recuperating the normal anterior chamber structure has potential benefit for the patients. As well, the procedures of performing GSL are very easy and safe. On the basis of the above reasons, we perform GSL for the patients with flat anterior chamber after trabeculectomy.
Because of the small number of patients in our case series and the relatively short follow-up, our study remains to be one of a preliminary nature. Clinical data in the present preliminary series demonstrated that EGSL was effective for the management of synechial ACG. Visual acuity was found to be improved after phacoemulsification-GSL in majority of the patients (11/12). The recurrence of PAS was quite limited in our case series. The surgeon could completely disinsert PAS in all quadrants with no intraoperative complication. It is interesting to know whether complete synechialysis reduces the recurrence of PAS.
The main limitation of the study include the small sample population (n=12), a relatively short follow-up time (mean: 7.4 mo), and the lack of a control group to compare this sample with a similar group of patients that may have undergone GSL with the conventional visualization system. To determine the best surgical approach for the treatment of ACG, we need large-scale randomized controlled trials to compare the efficacy of all the options mentioned, namely trabeculectomy, lens extraction, phacotrabeculectomy, GSL, phaco-GSL, and GSL combined with trabeculectomy.
As intraocular microendoscopy provides a clear and higher magnified view of the chamber angle irrespective of the media, application of this method to GSL enhances the accuracy, safety, and convenience of the surgical procedure.
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Keywords:© 2010 Lippincott Williams & Wilkins, Inc.
angle-closure; glaucoma; goniosynechialysis; endoscopy