TY - JOUR
T1 - Crowding and visual acuity measured in adults using paediatric test letters, pictures and symbols
AU - Lalor, Sarah J.H.
AU - Formankiewicz, Monika A.
AU - Waugh, Sarah J.
N1 - Funding Information:
Sarah J. H. Lalor was funded by an Anglia Ruskin University Graduate Teaching Assistantship . This study was funded in part by a grant from the Evelyn Trust , Cambridge, U.K. Portions of this work were presented at The European Academy of Optometry and Optics annual conference in 2012.
Publisher Copyright:
© 2016 The Authors.
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2016/4/1
Y1 - 2016/4/1
N2 - Crowding refers to the degradation of visual acuity for target optotypes with, versus without, surrounding features. Crowding is important clinically, however the effect of target-flanker spacing on acuity for symbols and pictures, compared to letters, has not been investigated. Five adults with corrected-to-normal vision had visual acuity measured for modified single target versions of Kay Pictures, Lea Symbols, HOTV and Cambridge Crowding Cards, tests. Single optotypes were presented in isolation and with surrounding features placed 0-5 stroke-widths away. Visual acuity measured with Kay Picture optotypes is 0.13-0.19 logMAR better than for other test optotypes and varies significantly across picture. The magnitude of crowding is strongest when the surrounding features abut, or are placed 1 stroke-width away from the target optotype. The slope of the psychometric function is steeper in the region just beyond maximum crowding. Crowding is strongest and the psychometric function steepest, with the Cambridge Crowding Cards arrangement, than when any single optotype is surrounded by a box. Estimates of crowding extent are less variable across test when expressed in units of stroke-width, than optotype-width. Crowding for single target presentations of letters, symbols and pictures used in paediatric visual acuity tests can be maximised and made more sensitive to change in visual acuity, by careful selection of optotype, by surrounding the target with similar flankers, and by using a closer target-flanker separation than half an optotype-width.
AB - Crowding refers to the degradation of visual acuity for target optotypes with, versus without, surrounding features. Crowding is important clinically, however the effect of target-flanker spacing on acuity for symbols and pictures, compared to letters, has not been investigated. Five adults with corrected-to-normal vision had visual acuity measured for modified single target versions of Kay Pictures, Lea Symbols, HOTV and Cambridge Crowding Cards, tests. Single optotypes were presented in isolation and with surrounding features placed 0-5 stroke-widths away. Visual acuity measured with Kay Picture optotypes is 0.13-0.19 logMAR better than for other test optotypes and varies significantly across picture. The magnitude of crowding is strongest when the surrounding features abut, or are placed 1 stroke-width away from the target optotype. The slope of the psychometric function is steeper in the region just beyond maximum crowding. Crowding is strongest and the psychometric function steepest, with the Cambridge Crowding Cards arrangement, than when any single optotype is surrounded by a box. Estimates of crowding extent are less variable across test when expressed in units of stroke-width, than optotype-width. Crowding for single target presentations of letters, symbols and pictures used in paediatric visual acuity tests can be maximised and made more sensitive to change in visual acuity, by careful selection of optotype, by surrounding the target with similar flankers, and by using a closer target-flanker separation than half an optotype-width.
KW - Crowding
KW - Paediatric visual acuity charts
KW - Psychometric function slopes
KW - Symbol and picture optotypes
KW - Visual acuity
UR - http://www.scopus.com/inward/record.url?scp=84958259588&partnerID=8YFLogxK
U2 - 10.1016/j.visres.2016.01.007
DO - 10.1016/j.visres.2016.01.007
M3 - Article
C2 - 26878696
AN - SCOPUS:84958259588
VL - 121
SP - 31
EP - 38
JO - Vision Research
JF - Vision Research
SN - 0042-6989
ER -