Decreased accommodation during decompensation of distance exotropia
- 1Infant Vision Laboratory, School of Psychology & Clinical Language Sciences, University of Reading, Reading, UK
- 2Department of Orthoptics, Royal Berkshire Hospital, Reading, UK
- Correspondence to Dr Anna Horwood, School of Psychology & Clinical Language Sciences, University of Reading, Earley Gate, Reading RG6 6AL, UK;
Contributors AMH is principal investigator on the funding award, and designed the study, and carried out ethics applications, recruitment, testing, data analysis, interpretation and writing. PMR was closely involved in study design and discussions on interpretation of data, and co-wrote the paper.
- Accepted 31 July 2011
- Published Online First 25 August 2011
Objective Disparity cues can be a major drive to accommodation via the convergence accommodation to convergence (CA/C) linkage, but, on decompensation of exotropia, disparity cues are extinguished by suppression so this drive is lost. This study investigated accommodation and vergence responses to disparity, blur and proximal cues in a group of distance exotropes aged between 4 and 11 years both during decompensation and when exotropic.
Methods 19 participants with distance exotropia were tested using a PlusoptiXSO4 photo refractor set in a remote haploscopic device that assessed simultaneous vergence and accommodation to a range of targets incorporating different combinations of blur, disparity and proximal cues at four fixation distances between 2 m and 33 cm. Responses on decompensation were compared with those from the same children when their deviation was controlled.
Results Manifest exotropia was more common in the more impoverished cue conditions. When decompensated for near, mean accommodation gain for the all-cue (naturalistic) target was significantly reduced (p<0.0001), with resultant mean under-accommodation of 2.33 D at 33 cm. The profile of near cues usage changed after decompensation, with blur and proximity driving residual responses, but these remaining cues did not compensate for loss of accommodation caused by the removal of disparity.
Conclusions Accommodation often reduces on decompensation of distance exotropia as the drive from convergence is extinguished, providing a further reason to try to prevent decompensation for near.
- Distance exotropia accommodation decompensation AC/A CA/C
- child health (paediatrics)
- treatment other
- optics and refraction
- visual perception
- experimental and laboratory
Funding This research was supported by a UK Department of Health Research Capacity Development Fellowship award PDA 01/05/031 to AMH.
Competing interests None.
Patient consent The study adhered to the tenets of the Declaration of Helsinki and was scrutinised and supervised by University of Reading and UK National Health Service Ethics Committees. Parents of children under 6 years of age gave fully informed consent on their behalf. Parents of children older than 6 years gave fully informed consent while the children themselves gave age-appropriate assent.
Ethics approval This study was conducted with the approval of the Berkshire NHS and University of Reading Research Ethics Committees.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The data form part of a much larger dataset that is still being analysed. No specific requirements for data sharing were specified by the funders, but it is possible that the whole dataset will eventually be stored centrally at the University of Reading and be made publically available.