Delayed acute angle closure after macular-hole surgery

Main

Sir,

Intraocular pressure (IOP) elevation is a common complication of pars plana vitreous surgery.¹ Acute glaucoma may occur in the postoperative period secondary to angle closure caused by surgical adjuvants such as long-acting expansile gases, silicone oil, and perfluorocarbon liquids; by postoperative inflammation, and by oedema of the ciliary body and anterior rotation of ciliary processes.^1,2,3,4 Macular-hole surgery predisposes to angle closure because of prolonged prone positioning and the routine use of cycloplegic agents postoperatively. Since surgery to close a macular hole is a relatively recent innovation, to our knowledge only two cases of angle-closure glaucoma following this surgery have been recorded.⁵ We report two further cases of acute angle-closure glaucoma following macular-hole surgery in patients with axial hypermetropia, in whom neither symptoms nor signs suggestive of angle closure existed preoperatively.

Case reports

Two hypermetropic women in their seventh and eighth decades of life were referred with a diagnosis of a unilateral macular hole (detailed clinical characteristics are summarized in Table 1). They had no past ocular or medical history of note and gave no history suggestive of intermittent angle closure. After dilatation with guttae tropicamide 1% and guttae phenylephrine 2.5%, the IOP was found to be within the normal range, and they did not experience any subsequent symptoms of angle closure. Preoperative gonioscopic examination was not undertaken in these patients as there was no obvious abnormality of the anterior chamber depth. They underwent a routine vitrectomy with epiretinal membrane and internal limiting membrane peel (under indocyanine green visualisation), followed by 15% perfluoropropane gas injection.

Table 1 Detailed clinical characteristics of the patients

Postoperatively, guttae dexamethasone 0.1% four times daily, guttae cyclopentolate 1% twice daily, and guttae chloramphenicol four times daily were prescribed, and they were instructed to posture face-down for 50 min every hour for 2 weeks. On the first postoperative day, the IOP was normal in both patients, with no evidence of pupillary block. The anterior chamber was formed and there was a 70–90% gas fill. At 1 week postoperatively, both patients developed an acutely painful red eye and reduced vision. Examination revealed an inflamed eye with corneal oedema and an IOP of 45 mmHg in the first case and 70 mm Hg in the second. The anterior chamber was noted to be shallow, and gonioscopy confirmed that the angle was closed in the operated eye and narrow but open in the fellow eye. In one case there was 30% gas fill and in the other about 75%. Prone positioning was stopped, the IOP was controlled with medical therapy, and bilateral peripheral YAG laser iridotomies were performed. After 1 week, the patients were asymptomatic and the IOP was normal.

Comment

In a hypermetropic phakic eye with a short axial length, and a relatively large lens, prone positioning shifts the lens–iris diaphragm anteriorly, thus shallowing the anterior chamber and narrowing the angle. This is likely to happen after prolonged face-down posturing following macular-hole surgery, and the regular use of guttae cyclopentolate postoperatively provides another risk factor for acute angle closure. A 15% perfluoropropane gas–air mixture is nonexpansile and is unlikely to have been responsible for the event as there was no gas-overfill, and the IOP was normal in both patients on the first postoperative day. Furthermore, by the time they presented with acute angle closure, the gas bubble was much smaller than in the immediate postoperative period. Resolution of the angle closure by a peripheral iridotomy rules out oedema of the ciliary body or anterior rotation of ciliary processes as being the primary causative factors.

It is evident from the above cases that the postoperative conditions following macular-hole surgery may provoke an attack of angle closure in an eye that on routine clinical evaluation may not be considered at high risk for spontaneous angle closure. All patients undergoing this surgery should be counselled about the risk of acute angle closure postoperatively. In addition, to decrease the possibility of postoperative pupillary block, gonioscopic examination should be undertaken in all hypermetropic patients who are undergoing macular-hole surgery, and a prophylactic YAG laser iridotomy should be performed in those with narrow angles. This may not entirely reduce the risk of acute angle closure, as this complication has been described following macular-hole surgery in an eye with a prophylactic YAG iridotomy.⁵ If the acute attack cannot be reversed then peripheral iridoplasty or goniosynechialysis could be considered.⁵ Combined phacoemulsification with lens implant and vitrectomy may also be an option and may be useful in some cases, as a significant proportion of these patients are likely to develop a cataract after the surgery.^6,7