Sir,

We wish to thank Dr Oguz for his correspondence regarding our report of ‘Sildenafil-associated consecutive nonarteritic anterior ischaemic optic neuropathy, cilioretinal artery occlusion, and central retinal vein occlusion in a haemodialysis patient’.1 Dr Oguz suggests that nonarteritic anterior ischaemic optic neuropathy (NA-AION) could not be explained by detrimental effect of sildenafil on the vascular supply of the optic nerve. He also adds that other factors could have been involved in NA-AION, cilioretinal artery occlusion, and central retinal vein occlusion.

The originality of this case presentation1 is that it is the first report of sildenafil-related NA-AION, cilioretinal artery, and central retinal vein occlusions. After the first attack of NA-AION in the left eye of the patient, which developed by ingestion of 100 mg of sildenafil for the first time the night before, the patient represented with a darkened superior visual field in his right eye for months later. Ignoring warnings against sildenafil, he had taken another 100 mg tablet. We think that the development of NA-AION in both eyes of the patient after ingestion of sildenafil is very important and must be taken into consideration by ophthalmologists and all general practitioners.

Dr Oguz's suggestion, which proposes that other factors could have been involved in NA-AION, cilioretinal artery occlusion, and central retinal vein occlusion, is valid. The pathogenesis of NAION is multifactorial, and includes structural and blood flow abnormalities and insufficient circulation in branches of the short posterior ciliary vessels.2 A 36-year-old male patient suffering from chronic renal failure which required haemodialysis three times a week was presented in our case report. Most patients on haemodialysis have cardiovascular pathology, with conditions such as atherosclerosis, anaemia, hypotension, and hypertension. Our patient had had episodes of hypotension during the day and night, and also after haemodialysis sessions, and he had a small cup-to-disc ratio. We suspect that the first sildenafil dose reduced arterial pressure significantly (most markedly at 1–2 h after administration), leading to NA-AION, cilioretinal artery occlusion, and central retinal vein occlusion.

Pomeranz and Bhavsar3 reported seven patients who had typical features of NA-AION within 36 h after ingestion of sildenafil citrate. They suggest that sildenafil may provoke NA-AION in individuals with an atherosclerotic risk profile. We think that patients need to know the potential ocular complications of sildenafil, and history of NA-AION should be a definite contraindication. Any prescription of this drug should require a detailed ophthalmologic examination and risk factor assessment before therapy is initiated especially in patients with an atheriosclerotic risk profile. We agree with Dr Oguz that more clinical/experimental multidisciplinary studies are needed to clarify all ocular effects of sildenafil.