Latent Nystagmus and DVD in Infantile Esotropia

This is a 20-year-old woman with infantile esotropia (s/p strabismus surgery as a child) who demonstrated latent nystagmus and presumed dissociated vertical deviation (DVD) OS, which are commonly seen with infantile esotropia (also inferior oblique overaction and monocular nasotemporal asymmetry to an optokinetic stimulus, other common features). Latent nystagmus changes direction depending upon the eye viewing - e.g., right-beating nystagmus with left eye occluded and left-beating nystagmus with right eye occluded. DVD is a condition where one eye drifts upwards and is commonly associated with infantile esotropia, although inferior oblique (IO) overaction can look similar. In her case, there was only subtle IO overaction with versions and ductions to the right and left. Her left eye drifted upward by the same amount regardless of the direction of gaze (e.g., in up, down, right and left gaze - would expect this mainly in adduction with pure IO overaction), so it was felt that the left upward drift was more related to DVD than IO overaction, although both could certainly have been contributing