Sir,

Peripheral iridoplasty using either argon or diode laser has been reported highly effective in lowering the intraocular pressure (IOP) in acute primary angle-closure (APAC).1 Rapid reduction of the IOP during APAC can result in decompression retinopathy.2, 3 We report two cases of decompression retinopathy following laser peripheral iridoplasty in two patients with APAC.

Case reports

Case 1: A 57-year-old Chinese woman presented with a 4-day duration bilateral APAC after taking antitussive (dextromethorphan HBr, phenylpropanolamine, promethazine). The vision was 6/20 and the IOP was 68 mmHg in both eyes. She had no history of hypertension but the blood pressure was transiently elevated to 177/100 mmHg at presentation. She had migraine treated with panadol and tenormin. She was also an α-thalassaemia trait. Her complete blood count and clotting profile were normal. She was treated with immediate argon laser peripheral iridoplasty, tiomolol, and pilocarpine eyedrops without systemic carbonic anhydrase inhibitor. The IOP was lowered within 30 min to 34 and 30 mmHg in the right and left eye, respectively. In 2 h, the IOP was 16 mmHg both eyes. Fundal examination at that time showed normal optic nerve head appearance in both eyes. On the next day before laser peripheral iridotomy was performed, the patient complained of a central scotoma in her left eye and the vision dropped to 6/120 while the right eye was 6/15. Examination revealed scattered pre- and intraretinal haemorrhages with involvement of the macula in her left eye and disc oedema in both eyes (Figure 1a and b). The haemorrhages and the disc oedema resolved completely after 4 weeks and the left eye vision returned to 6/15 (Figure 1c and d).

Figure 1
figure 1

(a) Left eye showing disc oedema and scattered retinal haemorrhages involving the macula. (b) Right eye showing disc oedema. (c) Left eye showing resolution of the retinal haemorrhages and disc oedema. (d) Right eye showing resolution of disc oedema.

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Case 2: A 57-year-old Chinese woman presented with a 12-h duration APAC in her left eye. She was healthy and blood investigations were normal. The vision at presentation was 6/60 and the IOP was 68 mmHg. She was treated with topical timolol, piolcarpine, and systemic aceazolamide. However, the IOP remained at 52 mmHg after 6 h. Diode laser peripheral iridoplasty was performed. The IOP decreased to 28 mmHg in 1 h. Fundal examination 2 h later showed a normal optic disc. On the next day before laser peripheral iridotomy was performed, she was found to have preretinal and vitreous haemorrhages in her attacked eye over the macula (Figure 2). At 4 months after the attack there was still residual blood clot in the vitreous. The vision returned to 6/9 and the IOP was 11 mmHg.

Figure 2
figure 2

Left eye B scan ultrasound showing preretinal haemorrhage.

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Comment

Decompression retinopathy has been reported in APAC following laser peripheral iridotomy.2,3 It was believed that the haemodynamic change associated with the sudden decrease in the markedly elevated IOP produced the retinal haemorrhage. Laser peripheral iridoplasty has been shown to lower the IOP rapidly in APAC.1 As a result of the rapid IOP reduction, it carries the risk of decompression retinopathy. The retinal and the vitreous haemorrhage in our patients could be explained by the sudden reduction of IOP. The disc oedema of the first patient could be explained by a forward shift of the lamina cribrosa with acute obstruction of the axonal flow from rapid reduction of the IOP. Our first patient had migraine and was also an α-thalassaemia trait both of which were associated with haematological and vascular abnormality. Whether these were the predisposing factors for the decompression retinopathy is unknown. In previous reports of decompression retinopathy following laser peripheral iridotomy in APAC, both patients were female in the 50–60 years age group. Our two patients are also females and in the 50 s. Female gender may not be a true risk factor and its predominance may be explained by the fact that APAC is more common in female.

Although decompression retinopathy usually presents with retinal haemorrhages and resolves spontaneously within a few weeks, it can lead to preretinal and vitreous haemorrhage and may take months to resolve. In our two patients, there was complete recovery of the visual acuity and there was no residual visual field defect at their last follow-up. Waheeb et al3 reported a case of decompression retinopathy following laser peripheral iridotomy and recommended significant IOP reduction before laser treatment. In our cases, the retinal haemorrhages and disc oedema occurred soon after laser peripheral iridoplasty before laser peripheral iridotomy was performed. This illustrated that the rapid IOP reduction itself might be the cause of the decompression retinopathy and lowering the IOP significantly before laser peripheral iridotomy may not necessarily prevent its occurrence. Although urgent IOP reduction is crucial in preventing irreversible nerve damage in APAC, the potential risk of decompression retinopathy from rapid IOP reduction using laser peripheral iridoplasty should be born in mind. We recommend thorough fundal examination after the acute attack is aborted.