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Spaceflight environmental factors may affect the nonvisual function of the retina, mediated by a reduction in melanopsin expression and ipRGC survival, contributing to circadian disruption.

Background The Heimann-Bielschowsky phenomenon (HBP) is an unusual form of monocular vertical pendular nystagmus and is usually asymptomatic. It always occurs in an eye with longstanding, profound visual loss. Reports of HBP are few and HBP is probably underdiagnosed. Recognition of HBP could prevent unnecessary and potentially harmful investigations. The purpose of this study was to report a series of patients with HBP and to summarise the international literature on the subject in order to better define the clinical presentation of HBP. Patients and Methods The study was approved by the local ethics committee. Medical records of patients diagnosed with HBP and examined by one of us (F. X. B.) were retrieved. Eye movements were quantified, either from video or eye tracking recordings, in all patients. The international literature on HBP was reviewed using the keywords “Heimann-Bielschowsky” or “monocular nystagmus”. Results From 2007 to 2017, we retrieved seven patients with HBP. In the literature, we found only 8 publications, accounting for 66 cases. In both our cases and those from the literature, VA was worse in the eye with HBP and was usually ≤ 20/200. Visual loss was either congenital or acquired and resulted from a variety of aetiologies. The eye movement was strictly monocular, pendular, mostly vertical, but sometimes oblique. Characteristically, its frequency was irregular but low (0.2 to 2.6 Hz in our cases, 0.05 to 5 Hz in the literature) and its amplitude very variable (1 to 9° and 1.5 to 50°, respectively). Extraocular movements were always preserved. Conclusions HBP is a benign monocular eye movement disorder that is always secondary to severe visual loss. Being asymptomatic, HBP is still under-recognised and easily overlooked. Furthermore, both amplitude and frequency of HBP may be small and irregular. Recognition of HBP is mandatory in order to prevent costly, unnecessary, and potentially hazardous investigations, and caution is advised, as cataract surgery might be responsible for postoperative oscillopsia.

Heimann-Bielschowsky phenomenon (HBP) is a rare form of dissociated nystagmus. 1 A 38year-old man complained of poor vision in his right eye for 6 years. Right visual acuity was 20/ 200 due to traumatic aphakia (cataract extraction without intraocular lens) and 20/20 in the left eye. An asymptomatic coarse, low frequency, pendular, vertical nystagmus was manifest in the right eye only (video, http://links.lww.com/WNL/A177). HBP is an asymptomatic monocular slow, pendular, mostly vertical nystagmus, which can develop years after uniocular severe visual loss. 1 The pathogenesis of HBP is debated, but vertical fusion disruption due to monocular visual loss is hypothesized. 2 Recognizing HBP should prevent unnecessary investigations or treatments. Author contributions Audrey Nguyen: drafting the manuscript, analysis of data. François-Xavier Borruat: revising the manuscript, study concept. Study funding No targeted funding reported.