a-Wave implicit time difference from post- to pre-treatment tests in treatment () v. control () groups. Ssd and Sh: with higher light intensity stimulation (Ssd and Sh: 3 and 10 cd·s/m2, respectively) in the dark-adapted state, a- and b-wave responses are obtained, demonstrating mixed rod and cone function. Pc: rods are desensitised using 30 cd·s/m2 of background light for 10 min, after which cones are stimulated using 3 cd·s/m2 in the light-adapted state. Values are means, with standard errors represented by vertical bars. Significant treatment × time interaction: ** P < 0·01. Ssd, electroretinography response from scotopic standard-intensity light stimulation; Sh, response from scotopic high-intensity light stimulation; Pc, photopic cone response.