The effect of flankers on three tasks in central, peripheral, and amblyopic vision

Dennis M Levi, Thom Carney
Journal of Vision 2011, 11 (1): 10
Using identical stimuli and methods, we assessed the effects of flankers on three different tasks, orientation discrimination, contrast discrimination, and detection, in central, peripheral, and amblyopic vision. The goal was to understand the factors that limit performance of a task in the presence of flankers in each of these visual systems. The results demonstrate that: (1) For unflanked targets, the losses in peripheral and amblyopic vision (relative to the normal fovea) are ordered, with the loss of unflanked contrast discrimination thresholds considerably smaller than those for either detection or orientation discrimination. (2) For flanked targets, in normal foveal vision and anisometropic amblyopia, the critical distance is more or less proportional to the target size, whereas in peripheral and strabismic amblyopic vision, the critical distance shows much less (or no) dependence on target size. (3) For the normal fovea, and anisometropic amblyopia, when the target is large (>≈0.2 deg) the amount of threshold elevation induced by flankers is low, increasing when the target is very small. On the other hand, for the periphery and the amblyopic eyes of most strabismic amblyopes, the elevation is large over the range of sizes tested. (4) In peripheral and strabismic amblyopic vision, remote flankers elevate orientation discrimination and contrast discrimination thresholds but not detection thresholds. Our results show clearly that the effects of flanks depend on both the task and the type of visual system. We conclude that in normal foveal vision and anisometropic amblyopia, the effects of flankers largely reflects a reduction in visibility and may be explained by masking. On the other hand, in peripheral vision and strabismic amblyopia, the effects of flankers on orientation discrimination and to a lesser extent contrast discrimination cannot be explained by simple masking and are due to crowding.

Full Text Links

Find Full Text Links for this Article


You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read

Save your favorite articles in one place with a free QxMD account.


Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"