Nystagmus is BEST described as which of the following?

• A. Eye swollen shut
• B. Inability to accommodate to light
• C. Rapid decrease in visual acuity
• D. Involuntary lateral movement of eye

Answer: (A)

Nystagmus is defined by rhythmic, involuntary movements of the eyeballs. The hallmark is that the eyes move on their own in a predictable, repetitive way, often side-to-side (horizontal) but can also be vertical or circular. This involuntary eye motion can disrupt gaze stability and is commonly related to vestibular or neurological issues. The other options describe conditions or symptoms that aren’t the defining feature of nystagmus—eye swelling, difficulty with accommodation, or a general rapid drop in visual acuity. Therefore, the best description is the involuntary lateral movement of the eye.