Fig. 3. lbk larvae show a strong visual impairment. (A) Optokinetic responses (OKRs) of 5dpf lbk and sibling larvae (n=6) stimulated with a sinusoidal grating. Although sibling larvae show a strong increase in eye tracking velocity with increasing contrast of the moving pattern, lbk mutants lack an OKR at all contrast levels, suggesting that the mutants are behaviourally blind. Error bars indicate standard deviations. The difference between wild-type and lbk larvae was significant at all levels of contrast. Significance was tested by inference statistics described by Rinner et al. (Rinner et al., 2005a) with a significance level of 5%. (B) Electroretinograms (ERGs) of 5 dpf lbk and sibling larvae measured over five log intensities of light. Mutant larvae (right) show a dramatically reduced b-wave compared with age-matched siblings (left). Red brackets indicate 100 ms light stimuli.