OCULAR GROWTH IN NEWBORN RABBIT EYES IMPLANTED WITH A POLY(METHYL METHACRYLATE) OR SILICONE INTRAOCULAR-LENS

Purpose: To examine eye growth in lensectomized infant rabbits implant ed with a poly(methyl methacrylate) (PMMA) or a silicone intraocular l ens (IOL). Setting: S:t Eriks Eye Hospital, Karolinska Institute, Stoc kholm, Sweden. Methods: Two groups of 3-week-old rabbits were used. In Group 1 (n = 13), lensectomy was performed in both eyes. In one rando mly selected eye, a +30 diopter (D) heparin-surface-modified (HSM) PMM A IOL was implanted in the capsular bag; the other eye was left aphaki c. In Group 2 (n = 10), a +21 D HSM PMMA IOL was implanted in one rand omly selected eye and a +21 D silicone IOL was implanted in the other. Axial length, corneal diameter, corneal thickness, and intraocular pr essure (IOP) were measured in all eyes preoperatively and 1, 2, and 3 months after surgery. The wet mass of the after-cataract was measured 3 months after surgery. The ciliary body with the ciliary processes an d the peripheral retina were examined histologically after formalin fi xation. The two IOL types were compressed to 7.0 mm, corresponding to the diameter of the 3-week-old rabbit lens. Results: In Group 1, the a xial length was significantly decreased in the eye with an HSM PMMA IO L compared with the fellow aphakic eye (P < .01, two-way analysis of v ariance [ANOVA]). No significant difference in corneal diameter, corne al thickness, or IOP was found between the eyes. The wet mass of the d issected after-cataract was significantly less in the eye implanted wi th an IOL. Two animals had an elevated IOP with secondary glaucoma in their aphakic eye and were excluded from the study. In Group 2, axial length in eyes with the HSM PMMA IOL was less than in the eyes with th e silicone IOL (P < .25, two-way ANOVA). No difference in corneal diam eter, corneal thickness, or IOP was found. The amount of after-catarac t was not altered. Histologically, the eyes with the HSM PMMA IOL show ed retinal degeneration, neovascularization of the ciliary body accomp anied by a large number of inflammatory cells, and tumid ciliary proce sses. The eyes with the silicone IOL showed only minor changes. The ap hakic eyes presented even less histological change. The compression te st demonstrated that three times the compression force was needed to s queeze the HSM PMMA lens than the silicone IOL. Conclusion: The result s suggest that in the young rabbit eye, implanting a regular-size HSM PMMA IOL destroys intraocular tissues and reduces eye growth significa ntly. Replacing the PMMA IOL with a silicone IOL improves the ocular g rowth.