Ludden, SM, Horwood, AM, Riddell PM Strabismus 2017: 25(3); 95-100
- We found that in naturalistic conditions, children did not always accommodate accurately on a near target.
- Although accommodation was better to small print, responses were very variable and often poorer than the literature would suggest is normal
Previous research indicates that a significant proportion of children underaccommodate at 1/3 m. Accommodation may vary with task demand, so children may accommodate appropriately if required, for example, when reading small print. This study explores the range of accommodative responses elicited in typical children, under naturalistic conditions, to a range of targets.
We identified 24 typically developing children from the University of Reading Child Database. Primary-school children attending UK Year 2 (age 6-7 years) or Year 6 (age 10-11 years) with minimum distance visual acuity of 0.200 logMAR and near visual acuity of 0.100 logMAR were recruited for participation. A remote haploscopic photorefractor was used to assess naturalistic, sustained, binocular accommodative responses to a variety of targets. At 33 cm, accommodative targets included individual letters, age-appropriate text in large print equivalent to early primary-school books, small N5 equivalent print, a visual search task (“Where’s Wally”), a clown picture containing a range of spatial frequencies, and a children’s cartoon. Participants were given minimal instructions for task completion. The target presentation order was counterbalanced. The results reported in this study were obtained during a longer testing session involving different target types and fixation distances.
The accommodative response observed with each target varied across participants to both the clown target and single letters of a size used in school reading books the accommodative responses were 2.4±0.48 D (range 0.85-2.97 D) and 2.47±0.37 D (range 1.48-3.09 D), respectively. The accommodative response to N5 print (3.06±0.52 D) was statistically better than all other targets other than the visual search and larger print tasks (P<0.05).
Even to demanding N5 text, accommodation is variable between participants, but is better than that to less demanding targets. Tasks experienced by children in everyday or clinical situations will stimulate an unknown amount of accommodation for near fixation.