The effects of field size and luminance on contrast sensitivity differences between specifically reading disabled and normal children.

Contrast sensitivity functions were measured for normal and specifically disabled readers in experiments which varied either field size or luminance level. The nature of the differences between groups was unaffected by field size, implying that spatial summation in specifically disabled readers is normal. Increasing luminance, however, increased the range over which disabled readers are less sensitive than normal readers. The results are discussed in terms of possible differences in underlying mechanisms.