Quantifying interactions between accommodation and vergence in a binocularly normal population

Laura E. Sweeney*, Dirk Seidel, Mhairi Day, Lyle S. Gray

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)
246 Downloads (Pure)


Stimulation of the accommodation system results in a response in the vergence system via accommodative vergence cross-link interactions, and stimulation of the vergence system results in an accommodation response via vergence accommodation cross-link interactions. Cross-link interactions are necessary in order to ensure simultaneous responses in the accommodation and vergence systems. The crosslink interactions are represented most comprehensively by the response AC/A (accommodative vergence) and CA/C (vergence accommodation) ratios, although the stimulus AC/A ratio is measured clinically, and the stimulus CA/C ratio is seldom measured in clinical practice. The present study aims to quantify both stimulus and response AC/A and CA/C ratios in a binocularly normal population, and determine the relationship between them. 25 Subjects (mean±SD age 21.0±1.9years) were recruited from the university population. A significant linear relationship was found between the stimulus and response ratios, for both AC/A (r 2=0.96, p<0.001) and CA/C ratios (r 2=0.40, p<0.05). Good agreement was found between the stimulus and response AC/A ratios (95% CI -0.06 to 0.24MA/D). Stimulus and response CA/C ratios are linearly related. Stimulus CA/C ratios were higher than response ratios at low values, and lower than response ratios at high values (95% CI -0.46 to 0.42D/MA). Agreement between stimulus and response CA/C ratios is poorer than that found for AC/A ratios due to increased variability in vergence responses when viewing the Gaussian blurred target. This study has shown that more work is needed to refine the methodology of CA/C ratio measurement.

Original languageEnglish
Pages (from-to)121-129
Number of pages9
JournalVision Research
Early online date18 Oct 2014
Publication statusPublished - Dec 2014


  • vergence
  • accommodation
  • oculomotor function

ASJC Scopus subject areas

  • Optometry
  • Neuroscience (miscellaneous)
  • Ophthalmology


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