Resting positions of vergence and their relation to asthenopic complaints.

Dark vergence is a resting position of vergence, measured in a dark visual field to eliminate fusional, accommodative, and proximal stimuli. Dark vergence differs among subjects: the average subject converges to a viewing distance of about 1 m, while the inter-individual range is from infinity to about 40 cm. This paper reviews previous ergonomic studies on dark vergence in relation to asthenopic complaints that occur when working at near computer screens: subjects with distant dark vergence exert more convergence and experience stronger asthenopic complaints than subjects with near dark vergence.

Objective vs subjective measurements of dark vergence.

Dark vergence is a resting position of vergence (tonic vergence), measured in a dark visual field to eliminate fusional, accommodative, and proximal stimuli. The vergence resting position is relevant for measures of phoria and fixation disparity. Dark vergence differs reliably among subjects: the average subject converges at a viewing distance of about 1 m, while the inter-individual range is from infinity to about 40 cm.