Results (see
Fig. 2) show that crowding magnitude (
Equation 1) depends on group (
F(2, 170) = 38.81;
P < 0.0001) being higher in strabismic amblyopic eyes (strab AE = 0.31 ± 0.14 logMAR), than in anisometropic amblyopic eyes (aniso AE = 0.11 ± 0.021 logMAR), fellow eyes (strab FE = 0.12 ± 0.012 logMAR, and aniso FE = 0.12 ± 0.018 logMAR) and healthy control eyes (RE = 0.093 ± 0.013 logMAR, the left eye (LE) = 0.094 ± 0.011 logMAR). Results were unaffected if data from the RE or LE of controls were used. Crowding magnitude also depended on the eye (
F(1, 170) = 53.23;
P < 0.0001) and age (
F(1, 170) = 426.54;
P < 0.0001). Post hoc comparisons revealed that crowding in control eyes was not different from that in fellow eyes of subjects with amblyopia (pediatric: aniso
P = 0.976 or strab
P = 1.000; juvenile/adult: aniso
P = 1.000 or strab
P = 0.987). Crowding was significantly higher for fellow and control eyes in the pediatric group, than in the juvenile/adult groups (pediatric: RE 0.16 ± 0.019 logMAR and the LE 0.16 ± 0.016 logMAR versus juvenile/adult: RE 0.028 ± 0.018 logMAR and the LE 0.025 ± 0.015 logMAR,
P < 0.0001; aniso FE: pediatric 0.21 ± 0.026 logMAR versus juvenile/adult 0.035 ± 0.024 logMAR,
P < 0.0001; strab FE: pediatric 0.17 ± 0.016 versus juvenile/adult 0.057 ± 0.018 logMAR,
P = 0.0001), but not in amblyopic eyes (aniso AE: pediatric 0.12 ± 0.031 versus juvenile/adult 0.094 ± 0.028 logMAR, both
P = 1.000 and strab AE: pediatric 0.31 ± 0.018 versus juvenile/adult 0.30 ± 0.021 logMAR). Crowding magnitude in strab AEs was higher than in control eyes in both age groups (pediatric:
P < 0.0001 and juvenile/adult:
P < 0.0001) and higher than in aniso AEs (pediatric:
P < 0.0001 and juvenile/adult:
P < 0.0001). It was not different between control eyes and aniso AEs (pediatric:
P = 0.989 versus juvenile/adults:
P = 0.584). Analyses conducted on five subgroups according to visual acuity (controls, low anisos, high anisos, low strabs, and high strabs) confirmed these results with one additional finding: no differences were found between crowding for low aniso versus high aniso groups (pediatric: low aniso AE 0.19 ± 0.047 versus high aniso AE 0.063 ± 0.041 logMAR,
P = 0.538; juvenile/adult: low aniso AE 0.090 ± 0.036 versus high aniso AE 0.10 ± 0.043 logMAR,
P = 1.000) or for low strab versus high strab groups (pediatric: low strab AE 0.35 ± 0.036 versus high strab AE 0.30 ± 0.021 logMAR,
P = 0.977; juvenile/adult: low strab AE 0.28 ± 0.041 versus high strab AE 0.31 ± 0.024 logMAR,
P = 1.000).