Dissociated vertical deviation (DVD): The saccadic and slow eye movements.

Area of Science:

• Ophthalmology
• Neuroscience
• Vision Science

Background:

• Dissociated vertical deviation (DVD) is a vertical strabismus often linked to infantile esotropia, latent nystagmus, and excyclotorsion.
• DVD typically manifests around three years of age, prompting investigation into its underlying cause.

Purpose of the Study:

• To investigate whether dissociated vertical deviation (DVD) originates from an abnormal motor vergence system or a broader visual system disorder.
• To characterize the eye movement dynamics during DVD to elucidate its pathophysiology.

Main Methods:

• Vertical eye movements of six subjects with DVD were analyzed using the magnetic search eye coil system during cover-uncover and alternate cover tests.
• Quantification of saccadic asymmetry during DVD upward movements and pure vertical saccades was performed.

Main Results:

• Three subjects exhibited smooth vertical divergence movements, while the other three showed a combination of smooth and asymmetrical saccade-like movements.
• Analysis of DVD latencies, peak velocities, time constants, and saccadic asymmetries provided insights into the movement characteristics.

Conclusions:

• The observed movement patterns, including latencies and saccadic asymmetries, suggest that dissociated vertical deviation (DVD) is a manifestation of an abnormal vertical vergence system.
• DVD appears to be primarily a motor system disorder rather than a generalized visual processing deficit.