Because of the young age of the chicks at the time of the surgery, the fellow eyes showed a gradual, relative myopic shift in their refractions over the monitoring period (
P < 0.001, repeated-measures ANOVA), a manifestation of normal emmetropization (
Fig. 3B ,
Table 1 ). Experimental eyes also underwent emmetropization. Thus, compared with their fellow eyes, the highly hyperopic eyes of the uncorrected LX group showed a greater myopic shift over the observation period (experimental vs. fellow:
P < 0.001, repeated-measures ANOVA,
Fig. 3B ,
Table 1 ). Partial correction of the lensectomy-induced hyperopia with a +20 D lens reduced but did not eliminate this myopic shift in refractive error (experimental vs. fellow:
P = 0.003, repeated-measures ANOVA;
Fig. 3B ,
Table 1 ). In contrast, the addition to LX eyes of a +30 D lens, which generally overcorrected the induced hyperopia, rendering them slightly myopic, induced a small hyperopic shift in refractive error (experimental vs. fellow:
P = 0.045, repeated-measures ANOVA,
Fig. 3B ,
Table 1 ). sham-surgery eyes wearing −30 D lenses (sham/−30 D) showed much greater and more consistent myopic shifts in refractive error than did the LX eyes over the same period, even though both groups were exposed initially to similarly large hyperopic focusing errors (
Table 1 , P < 0.001, repeated-measures ANOVA). The changes in the sham/−30 D group also differed significantly from those of the two lens-treated LX groups (sham/−30 D vs. LX/+20 D,
P < 0.001; sham/−30 D versus LX/+30 D group,
P < 0.001, repeated-measures ANOVA). There also were significant intergroup differences in the changes in the refractive errors of the three LX groups (
P = 0.02, repeated-measures ANOVA), with differences being significant for LX/+30 D versus LX/+20 D (
P = 0.020) and LX/+30 D versus LX (
P = 0.004), but not for LX versus LX/+20 D (one-way ANOVA; LSD multiple comparisons).