The Heimann-Bielschowsky Phenomenon: A Retrospective Case Series and Literature Review.

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.