BACKGROUND/AIMS: To investigate crowding ratios in children with a visual impairment due to ocular disease (n = 58) and normally sighted children (n = 75) aged 4 to 8 years using several variants of two clinically available tests with different optotype spacing (fixed or proportional to the optotype size). METHODS: Crowding ratios, calculated by dividing the single acuity by the linear acuity, were measured binocularly with the C-test and the LH line chart. Ratios >1.00 indicate crowding. RESULTS: The charts with fixed spacing revealed significantly higher crowding ratios for visually impaired children than normally sighted children (both for measurements at 40 cm and 5 m). The age-related reduction of the crowding ratios seen in normally sighted children when tested with near-vision charts with fixed spacing was not present in the visually impaired group. Visually impaired children with nystagmus showed higher crowding ratios than visually impaired children without nystagmus. The chart with proportional intersymbol spacing (ISS) did not reveal differences between the normally sighted and visually impaired children; nor did it show group, age, or nystagmus effects. CONCLUSION: Visually impaired children showed higher crowding ratios than normally sighted children when measured with charts with fixed ISS. This study illustrates that test design and target/flanker interference as a manifestation of crowding are critical issues to bear in mind when assessing crowding ratios in children.
BACKGROUND/AIMS: To investigate crowding ratios in children with a visual impairment due to ocular disease (n = 58) and normally sighted children (n = 75) aged 4 to 8 years using several variants of two clinically available tests with different optotype spacing (fixed or proportional to the optotype size). METHODS: Crowding ratios, calculated by dividing the single acuity by the linear acuity, were measured binocularly with the C-test and the LH line chart. Ratios >1.00 indicate crowding. RESULTS: The charts with fixed spacing revealed significantly higher crowding ratios for visually impaired children than normally sighted children (both for measurements at 40 cm and 5 m). The age-related reduction of the crowding ratios seen in normally sighted children when tested with near-vision charts with fixed spacing was not present in the visually impaired group. Visually impaired children with nystagmus showed higher crowding ratios than visually impaired children without nystagmus. The chart with proportional intersymbol spacing (ISS) did not reveal differences between the normally sighted and visually impaired children; nor did it show group, age, or nystagmus effects. CONCLUSION: Visually impaired children showed higher crowding ratios than normally sighted children when measured with charts with fixed ISS. This study illustrates that test design and target/flanker interference as a manifestation of crowding are critical issues to bear in mind when assessing crowding ratios in children.
Authors: Bianca Huurneman; F Nienke Boonstra; Cornelis A Verezen; Antonius H N Cillessen; Ger van Rens; Ralf F A Cox Journal: Graefes Arch Clin Exp Ophthalmol Date: 2013-03-16 Impact factor: 3.117
Authors: Bianca Huurneman; F Nienke Boonstra; Ralf Fa Cox; Antonius Hn Cillessen; Ger van Rens Journal: BMC Ophthalmol Date: 2012-07-23 Impact factor: 2.209
Authors: Daniëlle G M Bosch; F Nienke Boonstra; Michèl A A P Willemsen; Frans P M Cremers; Bert B A de Vries Journal: BMC Ophthalmol Date: 2014-05-01 Impact factor: 2.209
Authors: Joyce Liebrand-Schurink; Ralf F A Cox; Ger H M B van Rens; Antonius H N Cillessen; Ruud G J Meulenbroek; Frouke N Boonstra Journal: Front Psychol Date: 2016-06-23
Authors: Karlijn Woutersen; Albert V van den Berg; F Nienke Boonstra; Thomas Theelen; Jeroen Goossens Journal: PLoS One Date: 2018-05-01 Impact factor: 3.240