Hydrogel intraocular lens experience with endocapsular implantation

A systematic overview of the incidence of posterior capsule opacification

OBJECTIVE

Reported rates of posterior capsule opacification (PCO) vary widely and are based on various definitions of PCO, varying lengths and intervals of follow-up, and the use of different surgical techniques, intraocular lens (i.o.l.) designs, and methods of IOL implantation. This study was designed to obtain a more precise overall estimate of the incidence of PCO and to explore factors that might influence the rate of PCO development.

DESIGN

A meta-analysis.

METHODS

Published articles were selected for study based on a computerized MEDLINE search of the literature and a manual search of the bibliographies of relevant articles. Articles meeting selected inclusion criteria were reviewed systematically, and the reported data were abstracted and synthesized using the statistical techniques of meta-analysis.

MAIN OUTCOME MEASURE

Pooled estimates of the proportion of eyes developing PCO at three postoperative timepoints--1 year, 3 years, and 5 years--were measured.

RESULTS

There is significant heterogeneity among published rates of PCO. The overall pooled estimates (95% confidence limits) of the incidence of PCO were 11.8% (9.3%-14.3%) at 1 year, 20.7% (16.6%-24.9%) at 3 years, and 28.4% (18.4%-38.4%) at 5 years after surgery. There is no evidence of a significant decline in PCO incidence during the study period.

CONCLUSIONS

Visually significant PCO develops in more than 25% of patients undergoing standard extracapsular cataract extraction or phacoemulsification with posterior chamber intraocular lens implantation over the first 5 years after surgery. Patient characteristics, surgical techniques, and differences in research design and reporting may account for some of the variability in reported rates. However, no specific factors were identified in the authors' analysis. More precise estimates of incidence and identification of risk factors for PCO will depend on the development of a standardized measurement of PCO and wider adoption of more rigorous study methodology.

Intraocular lens implantation in infants with congenital cataracts

We evaluated 21 eyes of 13 infants between two and eight months old who had primary posterior chamber intraocular lens (IOL) implantation for congenital cataracts between 1988 and 1993. Twelve eyes had a posterior capsulorhexis or plaque peeling at the time of implantation and one eye had a vitrectomy. Eight eyes had no posterior capsule procedure during the initial surgery. Follow-up ranged from six months to five years. All eyes developed one or multiple posterior synechias and all, except one, required secondary capsulectomy and vitrectomy between one month and one year. Twenty eyes attained stable IOL fixation and a clear visual axis. In one eye, the IOL decentered downward. Patients with bilateral cataracts had greater visual improvement than those with a cataract in one eye only. No patient could manage spectacles postoperatively. Our findings show the benefits of posterior capsulectomy and anterior vitrectomy done in the early postoperative period and that IOL implantation in infants is a reasonable treatment in some parts of the world.

Results of intraocular lens implantation in paediatric aphakia

Intraocular lenses were implanted in 16 eyes of 13 patients with congenital cataract, and visual progress was plotted using a preferential-looking technique. Initial surgery was by lens aspiration with preservation of the posterior capsule, and subsequent posterior capsulotomy without anterior vitrectomy. Poly-HEMA posterior chamber lenses were used, usually as a primary procedure but in four cases as a secondary procedure after contact lens failure. No serious complications were encountered. Most eyes achieved a very significant visual improvement, and none were worse than preoperatively. Residual refractive error was highly unpredictable, but did not exceed 6 dioptres. The importance of rigorous occlusion therapy is stressed. With close follow-up, this procedure offers an effective and safe method for the correction of unilateral paediatric aphakia, and, in selected cases only, for bilateral aphakia.

Lens epithelial cells adhere less to HEMA than to PMMA intraocular lenses

Following cataract surgery proliferation of residual lens epithelial cells may occur causing secondary opacification and loss of visual acuity. Using an in vitro system the abilities of bovine and porcine lens epithelial cells to adhere to two types of intraocular lens have been assessed. Lens epithelial cells adhere significantly less to lenses composed of poly 2 hydroxyethylmethacrylate (HEMA) than to polymethylmethacrylate (PMMA).

Evaluation of 150 consecutive cases of poly HEMA posterior chamber lenses implanted in the bag using a small-incision technique

We report the results of 150 capsular bag implantations of the IOGEL PC-12 hydrogel lens. Mean follow-up was seven months. Following capsulorhexis and phacoemulsification, a Faulkner folder was used to insert the lens through a 3.5 mm to 4.0 mm scleral tunnel incision. Initially, a number of surgical complications were encountered. Because of increasing experience and modified instrumentation and technique, these did not occur in the later cases. Visual results were good, all eyes gaining a best case visual acuity of 20/40 or better and 97% achieving 20/25 or better. Morphological results were satisfactory. Generally the lenses remained centered and at a distance from the iris. Retention of viscoelastic substance or debris between the lens and the posterior capsule, occasionally observed at the start of the series, has been avoided by retrolental aspiration. Persistent pigment dispersion, which was observed when the lens had been implanted in the sulcus, was not seen. Tolerance of the lens material was generally satisfactory. There were six cases (4%) of fibrinoid uveitis, which is a relatively high incidence. From our experience and results we conclude that this implantation procedure allowed controlled insertion and placement of the IOGEL lens, provided that adequate instrumentation and technique was used; visual performance was comparable to that of poly(methyl methacrylate) lenses; capsular bag fixation furnished satisfactory morphological results, provided an adequately shaped capsulorhexis was performed.

Results of the intercapsular technique with the IOGEL lens

Standard biconvex 12 mm diameter IOGEL PC-1 hydrogel intraocular lenses were inserted into the eyes of 55 patients using intercapsular in-the-bag placement and extracapsular ciliary sulcus placement. All patients had senile cataracts. Endothelial specular microscopic assessment was performed preoperatively and postoperatively at six and 12 months. Viscoelastic agents were not used in any of the cases and upper haptic positioning was achieved with dialing and irrigation and iris retraction in each group, respectively. Major complications in both groups were iridocapsular synechias. This resulted in dislocation of a single haptic into the anterior chamber angle in one ciliary-sulcus-placed lens and in an updrawn pupil in one of the intercapsular cases. Pigment dispersion syndrome occurred in one case with a ciliary-sulcus-placed lens. In one case in each group a Nd:YAG laser posterior capsulotomy was performed. Whereas the visual results in each group were similar, the percentage cell loss was significantly greater in the group with lenses in the ciliary sulcus at six months postoperatively. The lower cell loss in the intercapsular group was attributed to the protective effect of the anterior capsule on the endothelium during the major intraocular manipulations.