Development of After-cataract in Pseudophakic Eyes with Silicone or PMMA Intraocular Lens

Foldable intraocular lenses(IOLs) arebeing used and wide spread with some advantages such asn little surgically induced astigmatism and rapid visual rehabilitation, but the effect of foldable IOLs on long-term safety and the formation of after-cataract was not understood clearly yet. 48 patients(54 eyes) which underwent Nd-YAG capsulotomy from 1995 to 1997 at the Kangnam St. Mary`s Hostpital were studied. All the cases had been operated by one operator(Joo) with the same technique except for incision method. The average interval from cataract surgery to Nd-YAG capsulotomy was 31 months in PMMA group and 15 months in silicone group. This difference between the two groups was statistically significant(P=0.0002). The ratio of Elschnig pearl type to fibrosis type in after-c attract was 16:6 in PMMA group and 13:18 in silicone group. The average of the total energy used in Nd-YAG laser capsulotomy was 256mJ in PMMA group and 309mJ in silicone group. However, damages caused by YAG laser were severer and more common on the silicone IOLs than on the PMMA IOLs. Silicone IOL induces after-cataract faster than PMMA IOL and the major type of after-cataract in pseudophakia with silicone IOL is fibrosis.

Postsurgical Inflammation Measured with Laser Flare Meter after Silicone or PMMA Intraocular Lens Implantation

It has been reported that silicone intraocular lens(IOL) induces severer and longer intraocular inflammation than polymethylmethacrylate(PMMA) IOL after extracapsular cataract extraction and IOL implantation. In order to evaluate the effect of IOL type on intraocular inflammation the authors measured the aqueous flare intensity by using the laser flare meter(FM 500 Kowa company) from postoperative one day to six months in 100 eyes with phacoemulsification followed by silicone IOL implantation (silicone group) and 100 eyes with phacoemulsification followed by PMMA IOL implantation(PMMA group). Every subject had a simple cataractous lens without systemic disease like diabetes or hypertension. There were no statistically significant differences between two groups in postsurgical aqueous flare intensity during the followed up period(p>0.05). The changes of aqueous flare intensity was spiking on the postoperative one day, declining rapidly in the first week and then keeping a steady state in both groups. Conclusively, we considered that surgically induced inflammation was not influenced by IOL type of PMMA or silicone in cataract operation without complication.

Effects on the surrounding tissues and morphological changes of components after implantation of PMMA and heparin surface modified PMMA intraocular lens in rabbit eyes

The aim of this study was to evaluate the cellular response and morphological changes of cells on the intraocular lens(IOL) implanted over a course of time and to identify the basic mechanism of IOL adaptation to tissue reaction in the implanted eye by comparing polymethylmethacrylate (PMMA) IOL with heparin surface modified PMMA IOL. ECCE using Healon was done in 36 eyes of 36 rabbits. A heparin surface modified IOL was implanted in 18 eyes (Group I), while PMMA IOL was implanted into another 18 eyes (Group II). Corneal thickness and endothelial cell density were measured for 3 months. Postoperatively, the eyes were enucleated, and a cytopathologic examination of the cells on the surface of the IOL and their ultrastructural changes were observed with light and scanning microscope at various points of time. The findings of this present study suggested that heparin surface modified PMMA IOL reduced the degree of endothelial cell damage, postoperative tissue reaction, and pigment deposits on the surface of the IOL. These were statistically significant. The most important cell was considered to be the macrophage for the adaptation of IOL in the eye which gradually changedinto a fibroblast-like cell, giant cell and finally disappeared after forming an acellular membrane on the IOL.

Effects on the Surrounding Tissues and Morphological Changes of Cellular Components after Implantation of PMMA and Heparin Surface Modified PMMA Intraocular Lens in Rabbit Eyes

The aim of this study was to evaluate cellular response and morphological changes of the cells on the intraocular lens(IOL) implanted according to the progress of time, and to identify the basic mechanism of IOL adaptation to tissue reaction in the implanted eye by comparing polymethylmethacrylate(PMMA) IOL with heparin surface modified PMMA IOL. ECCE using Healon(R) was done in thirty-six eyes of thirty six rabbits. A heparinsurface modified IOL was implanted in 18 eyes(Group I) while PMMA IOL into another 18 eyes(Group II). Corneal thickness and endothelial cell density were measured for three months. Postoperatively, eyes were enucleated and cytopathologic examination of cells on the surface of the IOL and their ultrastructual changes were observed with light and scanning microscope at various points of time. This finding of present study suggested heparin surface modified PMMA IOL reduced the degree of endothelial cell damage, postoperative tissue reaction and pigment deposits on the surface of the IOL. These were statistically significant. The most important cell was considered to be the macrophage for the adaptation of IOL in the eye and they gradually changes into fibroblast-like cell, giant cell and disappeared finally after forming acellular membrane on the IOL.

Comparison of Corneal Endothelial Cell Damage with Intraocular Lenses

The damage of corneal endothelial cell was studied among the 3 groups into which posterior chamber lenses of PMMA IOL, soft IOL(Hydrogel(R), and heparin surface modified PMMA IOL had been placed after planned extracapsular cataract extraction. The subjects were 76 eyes and the damage was assessed through measurement of central corneal endothelial cell density with specular microscope for 90 days. The mean corneal endothelial cell loss at 7th day of postoperative period was 9.2% in PMMA IOL group, 9.8% in soft IOL group, and 5.6% in heparin surface modified PMMA IOL group respectively. The heparin surface modified PMMA IOL group showed significant reduction of endothelial cell loss in contrast to the others at 7th day of postoperative period(p<0.05). There was no significant difference statistically in corneal endothelial cell density among the 3 groups at 30th day and 90th day of postoperative periods respectively.