Abstract
Purpose: :
Neuroscientists at MIT have shown that congenitally blind people with recoverable optical vision exhibit acceptable performance in visual acuity, color vision and other low-level visual tests but have some profound deficits in the interpretation of these images (Ostrovsky et al, 2009). The most notable deficits are a disruption of visual segmentation in which overlapping regions of line-drawn or transparent objects are seen as separate objects and of visual binding in which parts of an object are not perceptually joined together as a single object. These and other deficits also appear in some neurological patients. This pattern of disruption in form vision can lead to mistaken diagnosis of deficits in low-level vision when using common optometric tests such as the Ishihara plates in which groups of similar dots must be joined together to form figures or numbers.
Methods: :
We have created visual acuity, CSF, and color vision tests that do not require segmentation and binding abilities. These are to be presented on iPads in conjunction with the existing high-level perceptual tests.
Results: :
In this form-agnostic paradigm, visual acuity and CSF are tested with a matching task for band-passed Landolt Cs of different contrasts. Color vision is tested using a matching task similar to the City University Color Test. These tests require no patient instructions beyond those for the perceptual tests, requiring only stimulus matching rather than color or pattern naming. Disruption of segmentation and binding should have little or no effect on the results.
Conclusions: :
Traditional optometric tests can be redesigned to avoid the effects of patient deficits in the processing of visual form. In addition, these tests require fewer patient instructions, can be used on laptop and tablet computers, and blend in with the procedures of the MIT perception test battery. The tests are designed for patients with neurological losses but are appropriate for all patients.
Keywords: shape, form, contour, object perception • perception • color vision