Main

Sir,

Aqueous drainage implants are successfully used in the treatment of severe cases of glaucoma that are refractory to standard antiglaucomatous surgery. However, complications following these implants can occur.1 In this paper, we report a case of acquired Brown's syndrome (ABS) that occurred 3 weeks following the surgical implantation of an Ahmed valve implant in the superior nasal quadrant of an eye with neovascular glaucoma. Unlike a previous report2 in which an Ahmed valve caused ABS because the implant was placed in a patient with a small orbit, in the present case there was no implant–orbital disproportion, and the ABS occurred presumably secondary to fibrosis and consequent shortening of the superior oblique tendon of the affected eye.

Case report

A 74-year-old male patient was admitted to our Glaucoma Service complaining of pain in the right eye (RE) during the last 3 months. He had been submitted to trabeculectomy in this eye in another hospital, 6 months previously. When first examined by our staff, his best-corrected visual acuity was 20/400 in the RE and 20/25 in the left eye (LE). Slit-lamp examination of the RE revealed a diffuse conjunctival hyperaemia, fibrosis in the superior temporal quadrant (area of previous trabeculectomy), mild corneal odema, hyphaema (1 mm), iris neovascularization, ectropion uveae, and discrete nuclear opacification of the lens; the LE was unremarkable. The intraocular pressure (IOP) was 62 mmHg in RE and 14 mmHg in LE. Gonioscopy revealed peripheral anterior synechia in 360° of the angle; the LE angle was open. Ophthalmoscopy revealed a pale optic disc with a cup/disc ratio of 0.9 in RE. In LE the cup/disc ratio was 0.3. Ocular motility was normal.

Fluorescein angiograms of the RE taken 1 year before were available and indicated that the patient had been previously affected by a central retinal arterial occlusion before developing neovascular glaucoma. The patient then received retinal pan-photocoagulation therapy as well as clinical treatment to decrease the IOP. Despite the retinal laser therapy and the maximally tolerated medication the IOP was 42 mmHg. Drainage implant (Ahmed valve, model AGV-S2) surgery was planned. The superior nasal quadrant was chosen as the location for the implant due to the fact that the superior temporal region was extremely fibrotic due to a previous trabeculectomy. Within the first few days postsurgery, the IOP was 15 mmHg. However, within 3 weeks of surgery the patient presented a hypotropic RE in the primary position, with limitation of elevation in all superior gazes, but greater in adducted position (Figures 1 and 2). The forced duction test of this eye showed a mechanical restriction of elevation in adduction, which characterizes an ABS. As the IOP was under control and the patient did not complain of the ocular deviation, we opted for observation alone with regular follow-up.

Figure 1
figure 1

Acquired Brown's syndrome 3 weeks after superior nasal placement of the Ahmed implant in the RE. Note the inability to elevate the RE in the adducted position.

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Figure 2
figure 2

(a) Observe the large fibrotic bleb in the superior nasal region of the RE. (b) Ultrasound of the same eye revealing that there was no implant–orbital disproportion.

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Comments

Aqueous drainage implants are currently used in the treatment of cases of glaucoma refractory to standard antiglaucomatous surgery. Despite the satisfactory results in the control of the IOP, multiple complications are associated with these implants, including hypotony, cataracts, choroidal effusion, and haemorrhage, corneal decompensation, flat anterior chamber, retinal detachment, endophthalmitis, tube or plate erosion, and hyphaema.1 Extraocular motility disturbances are not rare following surgery with these drainage devices. In fact, muscle palsies, ABS syndrome, and generalized restrictions can occur.1

Ball et al3 described the first case of ABS secondary to a drainage valve implant, in this case a Baerveldt type, which was placed in the superior nasal quadrant of a glaucomatous eye of a patient with Cogan–Reese syndrome. The authors thought that the ABS resulted from expansion of the fibrous capsule around the bleb, causing a mechanical restriction and capture of the superior oblique tendon. Later, Dobler et al4 and Dobler-Dixon et al1 described four cases of ABS following a double-plate Molteno implant. ABS has also been reported secondary to a Krupin valve.5 In these previously mentioned papers, the patients had the drainage device implanted in the superior nasal quadrant of the affected eyes. Prata Jr et al5 suggested that the restriction of ocular motility was due to the presence of large filtering blebs or increased inflammation and scar formation in the superior nasal quadrant. These authors also hypothesized that the size of the implant was a predisposing factor for the development of ocular motility disturbances. Nevertheless, even with smaller implants, like Ahmed's type, these problems can occur. Indeed, Coats et al2 described a case in which the primary cause of ABS was the disproportion between the orbital size and the Ahmed implant, since ocular deviation began immediately after surgery.

In the present case, there was no disproportion between the size of the orbit and the implant, which demonstrated that even with the use of an implant of a regular size (Ahmed), limitation of ocular motility could occur due to fibrosis. This fibrotic reaction presumably caused a shortening of the superior oblique tendon, causing limited elevation in the adduction of the affected eye of our patient.

In selected cases in which the superior nasal region is the only possible place to implant the device, one must choose those with small areas of drainage and the procedure must be performed with the least inflammatory stimuli. Moreover, patients must be informed about the possibility of postoperative complications such as ocular motility abnormalities and diplopia.