Effect of horizontal vergence on the motor and sensory components of vertical fusion.

PURPOSE To compare motor and sensory capabilities for fusion of vertical disparities at different angles of horizontal vergence in healthy humans. METHODS Eye movements were recorded from both eyes of 12 healthy subjects using three-axis search coils. The stimulus was a cross (+) (3.4 x 3.2 degrees , vertically and horizontally, respectively) presented to each eye with a stereoscopic display. Vertical disparities were introduced by adjusting the vertical position of the cross in front of one eye. The disparity was increased in small increments (0.08 degrees ) every 8 seconds. Viewing was defined as "near" if there was a horizontal disparity that elicited 6 degrees to 15 degrees convergence, depending on the subject's capability for horizontal fusion; viewing was defined as "far" at 1 degrees convergence. Maximum motor (measured), sensory (stimulus minus motor), and total (motor plus sensory) vertical fusion were compared. RESULTS In 9 (75%) of 12 subjects the maximum total vertical fusion was more in near than in far viewing. The three who did not show this effect had relatively weak horizontal fusion. For the entire group, the motor component differed significantly between far (mean, 1.42 degrees ) and near (mean, 2.13 degrees). Total vertical fusion capability (motor plus sensory) also differed significantly between far (mean, 1.68 degrees ) and near (mean, 2.39 degrees ). For the sensory component there was no difference between between far (mean, 0.268 degrees ) and near (mean, 0.270 degrees ). As vertical disparity increased in a single trial, however, there was a small gradual increase of the contribution of the sensory component to vertical fusion. CONCLUSIONS Vertical fusion capability usually increases with convergence. This increase is caused primarily by an increase in the motor component. There is a gradual but small increase in the sensory component as target disparity slowly increases.

[1]  L. Hardy,et al.  Routine Examinations of the Ocular Muscles and Nonoperative Treatment , 1927 .

[2]  A L Duwaer.  Nonmotor component of fusional response to vertical disparity: a second look using an afterimage method. , 1982, Journal of the Optical Society of America.

[3]  J. Steen,et al.  Unequal amplitude saccades produced by aniseikonic patterns: Effects of viewing distance , 1995, Vision Research.

[4]  H. Collewijn,et al.  Human gaze stability in the horizontal, vertical and torsional direction during voluntary head movements, evaluated with a three-dimensional scleral induction coil technique , 1987, Vision Research.

[5]  Andrew E. Kertesz,et al.  Measurement of human vertical fusional response , 1978, Vision Research.

[6]  David S. Zee,et al.  Control oil vertical eye alignment in three-dimensional space , 1995, Vision Research.

[7]  Patterns of eye-hand dominance in baseball players. , 1988 .

[8]  Clifton M. Schor,et al.  Isovergence surfaces: the conjugacy of vertical eye movements in tertiary positions of gaze , 1994, Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians.

[9]  Christopher W. Tyler,et al.  Spatio-temporal properties of Panum's fusional area , 1981, Vision Research.

[10]  C M Schor,et al.  Distance cues for vertical vergence adaptation. , 1995, Optometry and vision science : official publication of the American Academy of Optometry.

[11]  H. Collewijn,et al.  Eye torsion associated with disparity-induced vertical vergence in humans , 1994, Vision Research.

[12]  K Sharma,et al.  Vertical fusion amplitude in normal adults. , 1992, American journal of ophthalmology.

[13]  Robert S. Allison,et al.  The dynamics of vertical vergence , 1997, Experimental Brain Research.

[14]  Martin J. Steinbach,et al.  Additivity of fuslonal vergence and pursuit eye movements , 1980, Vision Research.

[15]  J. T. Enright,et al.  Unexpected role of the oblique muscles in the human vertical fusional reflex. , 1992, The Journal of physiology.

[16]  M. Mets,et al.  Vertical Fusional Vergences in Patients with Superior Oblique Muscle Palsies , 1990 .

[17]  S. Véronneau-Troutman.  Fresnel prism membrane in acquired extraocular muscle palsy. , 1974, The American orthoptic journal.

[18]  H. Collewijn,et al.  Instability of ocular torsion during fixation: Cyclovergence is more stable than cycloversion , 1994, Vision Research.

[19]  B. Julesz,et al.  Extension of Panum's fusional area in binocularly stabilized vision. , 1967, Journal of the Optical Society of America.

[20]  Tutis Vilis,et al.  Rotation of Listing's plane by horizontal, vertical and oblique prism-induced vergence , 1995, Vision Research.

[21]  Clifton M. Schor,et al.  Context-specific adaptation of vertical vergence to correlates of eye position , 1997, Vision Research.

[22]  P. Romano,et al.  Patterns of eye-hand dominance in baseball players. , 1988, The New England journal of medicine.

[23]  Experimental investigation of vertical fusional movements. , 1949, American journal of optometry and archives of American Academy of Optometry.

[24]  M J Steinbach,et al.  Additivity of fusional vergence and pursuit eye movements. , 1980, Vision research.

[25]  D. Straumann,et al.  Transient torsion during and after saccades , 1995, Vision Research.

[26]  R. Rutstein.  Vertical vergence adaptation for normal and hyperphoric patients. , 1992, Optometry and vision science : official publication of the American Academy of Optometry.

[27]  Vertical Fusional Response to Asymmetric Disparities , 1983, IEEE Transactions on Biomedical Engineering.

[28]  Clifton M. Schor,et al.  An adaptable association between vertical and horizontal vergence , 1995, Vision Research.

[29]  G. K. Noorden,et al.  Binocular vision and ocular motility;: Theory and management of strabismus , 1974 .

[30]  Z. Kapoula,et al.  Disconjugate Adaptation of the Vertical Oculomotor System , 1996, Vision Research.

[31]  H. Collewijn,et al.  Precise recording of human eye movements , 1975, Vision Research.