Which form is most similar to end-point nystagmus but includes additional ocular motor abnormalities?

• A. Gaze-evoked nystagmus
• B. Spasmus nutans
• C. Latent nystagmus
• D. Convergence-retraction syndrome

Answer: (A)

End-point nystagmus is a gaze-holding phenomenon that appears when the eyes reach the far edge of their range, reflecting a limitation in maintaining fixation at an extreme gaze. The form that is most similar but includes additional ocular motor abnormalities arises when the eyes cannot hold an eccentric position over time due to a defective neural integrator. This leads to a drift back toward midline followed by a corrective saccade, producing a nystagmus that is not only present at eccentric gaze but often accompanied by other signs such as rebound movements, dysmetric or erroneous saccades, and impaired pursuit. In other words, it shares the gaze-holding nature of end-point nystagmus but brings extra ocular motor abnormalities because the system that normally sustains eccentric gaze is not functioning properly.

Other described conditions differ in their typical context and signs: spasmus nutans occurs in infancy with a triad of nystagmus, head bobbing, and head turning; latent nystagmus emerges and changes with binocular vision (often seen when one eye is occluded); convergence-retraction syndrome is a dorsal midbrain syndrome with upgaze limitation and convergence-retraction on attempted upgaze.