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To crowd or not to crowd? The influence of surrounding contours on measures of visual acuity
Author(s) -
BARRETT BT
Publication year - 2010
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2010.4425.x
Subject(s) - crowding , crowding out , reading (process) , psychology , cognitive psychology , linguistics , philosophy , monetary economics , economics
Purpose Crowding refers to the finding that visual acuity (VA) for isolated letters is better than the VA measured when the letters to be identified are flanked by other letters. Although crowding was first described over 50 years ago, it remains the subject of much research interest. Here, I summarise the reasons why crowding is so important and the current thinking about it. Methods Crowding is important for at least three reasons: (1) Children and amblyopes suffer more from the effects of crowding. Accurate VA measures are a key component of attempts to detect and diagnose visual disorders that first emerge in early life but whose effects can last a lifetime. (2) Following on from (1), crowding has had, and continues to have, a major influence on VA test‐chart design. This is because crowded VA scores can’t easily be predicted from unflanked VA scores. (3) Until recently, crowding was studied only from the perspective of its influence on VA measures. However, it is now recognised that crowding influences not just the ability to identify letters but all kinds of object recognition. For example, eye care professionals need to be aware that crowding limits reading speed, and hence that changes to letter/word spacing can improve reading proficiency. Results Recent research findings greatly simplify the story about crowding, but they also highlight how the significance of crowding for eye care professionals extends well beyond VA measurement. Conclusion Crowding has important implications for patients both in the clinic and for their everyday activities, most notably in relation to reading. With greater understanding of crowding, we are in a better position to help and advise our patients.