Keeping an Eye on Optic Neuritis Studies in Mainland China

We read with great interest the review article by Dr. Woung and associates.1 They reviewed the recent important studies on optic neuritis in Asia, and compared them with those in Western countries. Their article included the studies addressed in Taiwan, Japan, India, and Singapore. However, several important studies in mainland China had not been included. We would like to review them in this letter. Almost all the studies in Asia that were published in the English language investigated unilateral and bilateral acute optic neuritis (AON) simultaneously. In the Optic Neuritis Treatment Trial (ONTT), however, the investigators only recruited the patients with unilateral AON.2 According to the literature, the proportion of bilateral AON in Asia is 25–33%.3 It is unsuitable to mix bilateral and unilateral AON, and to compare them with ONTT due to the significantly different features of bilateral and unilateral AON. In mainland China, Dr. Du described unilateral and bilateral AON separately,3,4 and found that bilateral AON has some clinical differences from unilateral AON, including a higher prevalence of male cases and disc swelling, and more severe initial visual loss, but quicker visual recovery.3 In our experiences, considerable Chinese patients with AON have a very poor visual prognosis.4,5 Dr. Lai and associates studied this subgroup of Chinese patients, and found that these patients have a high positive rate of anti-aquaporin-4 antibody (neuromyelitis optica immunoglobulin G),6,7 which is a highly sensitive and specific antibody in patients with neuromyelitis optica. For this reason, Dr. Lai’s studies had partly demonstrated the hypotheses proposed by Dr. Du, that a proportion of Chinese patients with AON might develop neuromyelitis optica during long-term follow-up, or might be a forme fruste of neuromyelitis optica.8 Although most knowledge of clinical aspects of optic neuritis is from the Optic Neuritis Treatment Trial, some cases in the Optic Neuritis Treatment Trial also had poor visual recovery, and the reason remains unclear, which is similar to the situation clinicians in China have to face almost every day. We hope our colleagues in the world keep an eye on optic neuritis studies in mainland China.