Sensitivity analysis of relative accommodation and vergence

A sensitivity analysis was performed to determine the variation in response to changes in parameter values of a previously developed nonlinear static model of accommodation and vergence. To determine normal behavior, model simulation responses were computed using previously obtained parameter values in 4 subjects under 2 conditions. In the first, relative accommodation was evaluated by maintaining the vergence stimulus constant at 2.5 meter angles (MA) and varying the accommodative stimulus from -2.5 to 2.5 diopters (D) in 0.25-D steps. In the second, relative vergence was evaluated by maintaining the accommodative stimulus constant at 2.5 D and varying the vergence stimulus from 25 prism diopters (PD) base-in to 25 PD base-out in 5-PD steps. Sensitivity of the model parameters, consisting of controller gains for accommodation (ACG) and vergence (VCG), crosslink gains for accommodation-to-vergence (AC) and vergence-to-accommodation (CA), deadspace operators for accommodation (AE/spl plusmn/AD) and vergence (VE/spl plusmn/VD), and the tonic levels for accommodation (ABIAS) and vergence (VBIAS) were assessed by varying them at 50% and 150% of their normal values. It was found that the accommodation and vergence systems mere most sensitive to variation in crosslink gain, moderately sensitive to variation in controller gain and tonic level, and least sensitive to variation in size of the deadspace. These results may provide a quantitative basis for the occurrence of ocular dysfunctions associated with abnormal crosslink gains, such as strabismus, in clinical patients.<<ETX>>

[1]  G. Hung.  Linear model of accommodation and vergence can account for discrepancies between AC/A measures using the fixation disparity and phoria methods , 1991, Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians.

[2]  G. B. Wetherill,et al.  SEQUENTIAL ESTIMATION OF POINTS ON A PSYCHOMETRIC FUNCTION. , 1965, The British journal of mathematical and statistical psychology.

[3]  R. Duckman.  The incidence of visual anomalies in a population of cerebral palsied children. , 1979, Journal of the American Optometric Association.

[4]  K N OGLE,et al.  Depth of focus of the human eye. , 1959, Journal of the Optical Society of America.

[5]  Kenneth J. Ciuffreda,et al.  AMBLYOPIA: BASIC AND CLINICAL ASPECTS , 1991 .

[6]  K. N. Ogle.  Researches in binocular vision. , 1950 .

[7]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[8]  George K. Hung,et al.  A Dual-Mode Dynamic Model of the Vergence Eye Movement System , 1986, IEEE Transactions on Biomedical Engineering.

[9]  L. Stark,et al.  Dynamic vergence eye movements in strabismus and amblyopia: asymmetric vergence. , 1981, The British journal of ophthalmology.

[10]  K. Ciuffreda,et al.  Static accommodation in congenital nystagmus. , 1993, Investigative ophthalmology & visual science.

[11]  W N Charman,et al.  Perceptual detectability of ocular accommodation microfluctuations. , 1989, Journal of the Optical Society of America. A, Optics and image science.

[12]  G. Brink,et al.  Diplopia thresholds and the initiation of vergence eye-movements , 1981, Vision Research.

[13]  Kenneth J. Ciuffreda,et al.  Vergence eye movements : basic and clinical aspects , 1983 .

[14]  George K. Hung,et al.  Static Behavior of Accommodation and Vergence: Computer Simulation of an Interactive Dual-Feedback System , 1980, IEEE Transactions on Biomedical Engineering.

[15]  D E Mitchell,et al.  A review of the concept of "Panum's fusional areas". , 1966, American journal of optometry and archives of American Academy of Optometry.

[16]  G K Hung,et al.  Quantitative assessment of disparity vergence components. , 1986, Investigative ophthalmology & visual science.

[17]  G Smith,et al.  Effect of Defocus on Blur Thresholds and on Thresholds of Perceived Change in Blur: Comparison of Source and Observer Methods , 1989, Optometry and vision science : official publication of the American Academy of Optometry.

[18]  G K Hung,et al.  Dual‐mode behaviour in the human accommodation system , 1988, Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians.

[19]  G.K. Hung.  Quantitative analysis of associated and disassociated phorias: linear and nonlinear static models , 1992, IEEE Transactions on Biomedical Engineering.

[20]  J. C. Kotulak,et al.  The Accommodative Response to Subthreshold Blur and to Perceptual Fading during the Troxler Phenomenon , 1986, Perception.

[21]  Campbell Fw.  A method for measuring the depth of field of the human eye. , 1954 .

[22]  M. De.  A review of the concept of "Panum's fusional areas". , 1966 .

[23]  Charles Sheard,et al.  ZONES OF OCULAR COMFORT , 1930 .

[24]  A. Kertesz,et al.  Fusional responses of strabismics to foveal and extrafoveal stimulation. , 1985, Investigative ophthalmology & visual science.

[25]  G K Hung.  Adaptation model of accommodation and vergence , 1992, Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians.

[26]  John D'Azzo,et al.  Linear Control System Analysis and Design: Conventional and Modern , 1977 .

[27]  R. Leigh,et al.  The neurology of eye movements , 1984 .

[28]  G. Hung.  Fixation disparity under open‐and closed‐loop accommodation , 1990, Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians.

[29]  Kenneth N. Ogle,et al.  Oculomotor imbalance in binocular vision and fixation disparity , 1968 .

[30]  G. Breinin,et al.  The effect of pupil size on accommodation, convergence, and the AC/A ratio. , 1962, Investigative ophthalmology.

[31]  J L Semmlow,et al.  Accommodative and fusional components of fixation disparity. , 1979, Investigative ophthalmology & visual science.