AC/A - CA/C - or neither? Why we should re-think some theoretical vergence-accommodation models.
Past Event Date:
Speaker:Professor Anna Horwood PhD DBO(T), University of Reading, Infant Vision Laboratory, School of Psychology & Clinical Language Sciences, UK
Room 204 - Main Conference Room
Clinicians are taught that the AC/A ratio (accommodation - convergence/accommodation) is an important theoretical concept which should influence patient care. Theoretical teaching on the management of binocular vision problems is often based on this “fixed and stable” relationship – but in practice, it is rarely used to change clinical decision-making, it is rarely measured, and the ratio which IS measured clinically is imprecise.
Scientists investigating vergence-accommodation models are still uncertain about what lies within these models and fail to explain how vergence-accommodation models behave in strabismus and anomalies of binocular vision.
While the AC/A relationship may be important for a small, select group of patients, the research in our laboratory suggests that, in general, the CA/C (convergence - accommodation/convergence) relationship is much more important in everyday conditions and many clinical situations.
My talk will outline how issues relating to the CA/C relationship can impact on patient care and our understanding of binocular vision. It will go on to discuss how both the AC/A and CA/C linkages may be more flexible than generally considered.
Most Recent Publications
- "Asymmetrical accommodation in hyperopic anisometropic amblyopia." Brit J Ophthalmol 2017 Published Online First: 19 October 2017 http://centaur.reading.ac.uk/72157/
- "Convergence and accommodation development is pre-programmed in premature infants." Investigative Ophthalmology & Visual Science, 56. pp. 5370-5380. http://iovs.arvojournals.org/article.aspx?articleid=2427530
- "Developmental changes in the balance of disparity, blur and looming/proximity cues to drive ocular alignment and focus." Perception, 42, 693-715 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4533891/
Review /discussion pieces
"Disparity-driven vs blur-driven models of accommodation and convergence in binocular vision and intermittent strabismus." Journal of the American Association of Pediatric Ophthalmology and Strabismus, 18 (6). pp. 576-583. http://www.sciencedirect.com/science/article/pii/S1091853114005187?via%3Dihub
Main methods paper for all subsequent papers:
"The use of cues to convergence and accommodation in naïve, uninstructed participants." Vision Research , 48(15), 1613-24 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4533892/