PURPOSE: To examine after-cataract and eye growth in lensectomized newborn rabbits implanted with capsule tension rings of different sizes. SETTING: S:t Eriks Eye Hospital, Karolinska Institute, Stockholm, Sweden. METHODS: Two groups of 24-day-old rabbits were used. In Group 1 (n = 9), lensectomy was performed in both eyes. In one randomly selected eye, an open poly(methyl methacrylate) (PMMA) capsule tension ring with a 7.0 mm diameter and 0.13 mm thickness was implanted in the capsular bag. The other eye was left aphakic. In Group 2 (n = 10), an open PMMA capsule tension ring with a 10.0 mm diameter and 0.13 mm thickness was implanted in one randomly selected eye, and the other eye was left aphakic. Axial length, corneal diameter, corneal thickness, and intraocular pressure (IOP) were measured in all eyes preoperatively and 1, 2, and 3 months after surgery. The wet mass of the after-cataract was measured at 3 months. Three Group 1 eyes and four Group 2 eyes developed secondary glaucoma and were excluded from the study. RESULTS: Axial growth did not differ significantly between the eyes implanted with the 7.0 mm ring and the aphakic eyes (mean difference 0.01 mm; F3;15 = 0.02; P > .25). Corneal diameter also did not differ (two-way analysis of variance [ANOVA]). Axial length growth was less in the eyes implanted with the 10.0 mm ring than in the aphakic eyes (mean difference 1.05 mm; F3;15 = 2.06; P .25; two-way ANOVA). Amount of after-cataract did not differ significantly between the aphakic eyes and the eyes implanted with the 7.0 mm ring. It was significantly less in the eyes with the 10.0 mm ring than in those with the 7.0 mm ring (Wilcoxon signed-rank test) and in the aphakic eyes (P