Downbeat nystagmus with a pseudocycloid waveform: improvement with base-out prisms

Area of Science:

• Neuro-ophthalmology
• Nutritional Neuroscience
• Medical Nutrition Therapy

Background:

• Prolonged intravenous therapy for hyperemesis gravidarum can lead to nutritional deficiencies.
• Nutritional deficiencies can manifest with neurological symptoms, including ocular motor abnormalities.
• Downbeat nystagmus is an involuntary eye movement disorder characterized by a downward drift.

Purpose of the Study:

• To describe a case of downbeat nystagmus and oscillopsia secondary to nutritional deficiency.
• To characterize the nystagmus waveform using advanced oculography.
• To evaluate the therapeutic efficacy of base-out prisms in managing convergence-induced nystagmus.

Main Methods:

• Case report of a patient with hyperemesis gravidarum and subsequent neurological symptoms.
• Wide bandwidth infrared oculography to record and analyze nystagmus characteristics.
• Clinical assessment of visual acuity and oscillopsia before and after prism prescription.

Main Results:

• The patient presented with downbeat nystagmus in the primary gaze position and oscillopsia.
• Oculography revealed a pseudocycloid nystagmus waveform with an increasing-velocity exponential slow phase.
• Addition of base-out prisms to spectacle lenses reduced oscillopsia and damped nystagmus, improving visual acuity.

Conclusions:

• Nutritional deficiency is a potential cause of acquired downbeat nystagmus.
• Infrared oculography can precisely characterize nystagmus waveforms.
• Base-out prisms can be an effective treatment for specific types of nystagmus and associated visual disturbances.