Five-year Follow-up of a Prospective Study Comparing Hydrogel with PMMA Single Piece Lenses

Retrospective evaluation of intraocular lenses in adults younger than 60 years

Data from the U.S. Food and Drug Administration, the American Academy of Ophthalmology's National Eyecare Outcomes Network, and Storm Eye Institute databases were analyzed for short- and long-term safety and efficacy outcomes of intraocular lens (IOL) implantation in adults younger than 60 years and 60 years and older. Statistical analyses for significance were performed where appropriate. A comprehensive literature review was conducted to identify safety and efficacy outcomes and their relationship to patient age at the time of implantation. Analyses established that the performance of IOLs in adults younger than 60 years was comparable to that in adults older than 60 years and supported the use of IOLs in the younger adult population.

The influence of implant design on accuracy of postoperative refraction

PURPOSE

To assess the degree of accuracy of postoperative refraction that may be achieved with modern techniques and a new lens of modern design.

METHODS

Five hundred eyes underwent refraction at one week and one month following phacoemulsification and implantation of the Centerflex lens (Rayner Intraocular Lenses Ltd style 570H). Results were compared with the target that had been computerised at the time of surgery, using the Hoffer Q formula for axial lengths less than 22.0 mm, the SRK-T for lengths greater than 24.5 mm and a mean of the two formulae for lengths between 22.0 and 24.5 mm. Statistical analysis used Fisher's exact and one way ANOVA tests.

RESULTS

At one month 97% of refractions were within 1.0 D spherical equivalent (SE) of target and 81% within 0.5 SE. The mean absolute error was 0.37 +/- 0.39 SD. 75.8% of all eyes achieved 6/12 unaided and 88.6% achieved 6/9 with correction. In only 1.2% the refraction between one week and one month had altered by 0.5 D or more.

CONCLUSIONS

The Centerflex when combined with modern methods of power calculation, can be associated with a high degree of accuracy in postoperative refraction.

Intraocular lens bioactivity tested using rabbit corneal tissue cultures

PURPOSE

To evaluate the effects of different intraocular lens (IOL) materials on epithelial cell growth to test the sandwich theory; i.e., a bioactivity-based explanation of posterior capsule opacification (PCO) after cataract surgery.

SETTING

Central Hospital, Vaasa, and Institute of Dentistry and Turku Center for Biomaterials, University of Turku, Finland.

METHODS

Rabbit corneal tissue cultures were set up on poly(methyl methacrylate) (PMMA), heparin-surface-modified (HSM) PMMA, silicone, acrylate, and hydrogel IOLs for 1 week. The tissue consisted of intact epithelium and half the thickness of the corneal stroma, which was placed against the IOL. The growth of the epithelium was examined by light microscopy to evaluate the attachment of the corneal explant to the IOL surface.

RESULTS

All tissue samples grew well under the culture conditions. When grown on PMMA, HSM PMMA, silicone, and hydrogel, the tissue did not attach to the IOL or the epithelium grew around the explant, suggesting that the attachment of the stroma to the IOL was poor or nonexistent. Some explants on acrylate IOLs attached directly to the IOL surface with no epithelial ingrowth between the stroma and the IOL.

CONCLUSIONS

This tissue culture method can be used to examine the behavior of corneal tissue in contact with different IOL materials. The results suggest that the acrylate IOL may have bioactive properties. This, with the lens optic's square edge, may hinder lens epithelial cell proliferation and thus prevent PCO.

12 year results of a prospective trial comparing poly(methyl methacrylate) and poly(hydroxyethyl methacrylate) intraocular lenses

PURPOSE

To compare long-term biocompatibility of single-piece poly(methyl methacrylate) (PMMA) and poly(hydroxyethyl methacrylate) (P-HEMA) intraocular lenses (IOLs).

SETTING

District General Hospital, United Kingdom.

METHODS

In a prospective trial of 250 eyes that had uncomplicated extracapsular cataract extraction, 2 groups of 125 eyes each were matched for age and sex. One group received single-piece looped PMMA IOLs and the other, single-piece solid-haptic P-HEMA IOLs. In all eyes, the IOLs were implanted in the capsular bag at the time of surgery using the envelope technique.

RESULTS

Twelve years after surgery, 75 eyes were available for examination. In the PMMA group (40 eyes), 50% had a visual acuity of 20/20 and 50% had intact capsules, many of them with a degree of fibrosis. In the P-HEMA group (35 eyes), 71% had an acuity of 20/20 and 80% had intact capsules (P = .0085).

CONCLUSION

In the long term, biocompatibility was better in the P-HEMA group than in the PMMA group.

Effect of intraocular lens and anterior capsule opening type on posterior capsule opacification

PURPOSE

To determine the effect of intraocular lens (IOL) type and anterior capsulectomy technique on the incidence of posterior capsule opacification.

SETTING

Department of Ophthalmology, Medical Faculty, University of Ondokuz Mayis, Samsun, Turkey.

METHODS

Three hundred two eyes of 294 patients were examined retrospectively after IOL implantation in the capsular bag performed between February 1991 and November 1996. Patients were divided into 3 groups according to IOL type: poly(methyl methacrylate) (PMMA); heparin-surface-modified PMMA (HSM PMMA); plate-haptic silicone. Envelope capsulectomy or continuous curvilinear capsulorhexis (CCC) was used. Mean follow-up was 27 months (range 12 to 33 months).

RESULTS

Posterior capsule opacification developed in 47 cases (15.6%): 21.7% in the PMMA lens group after planned extracapsular cataract extraction (ECCE), 17.4% in the HSM PMMA lens group after planned ECCE, and 7.7% in the plate-haptic silicone lens group after phacoemulsification. Posterior capsule opacification occurred less in patients who had anterior capsulectomy using the CCC technique (11.5%) than in those having an envelope capsulectomy (24.5%) (P < .05). Posterior capsule opacification was significantly less in eyes with a capsular-bag-fixated plate-haptic silicone lens than in those with a PMMA or HSM PMMA IOL (P < .05).

CONCLUSION

This study demonstrated that the anterior capsulectomy technique and the IOL type influence the incidence of PCO.

Evaluation of the first 50 ACR360 acrylic intraocular lens implantations

PURPOSE

To evaluate the clinical results of implantation of the ACR360 soft acrylic intraocular lens (IOL).

SETTING

Civico Hospital, Lugano, Switzerland.

METHODS

This prospective, medium-term study comprised the first 50 consecutive patients who had small incision scleral tunnel phacoemulsification and implantation of an ACR360 acrylic IOL (loptex/Allergan). Intraoperative and postoperative complications, best corrected visual acuity (BCVA), intraocular pressure (IOP), preoperative and postoperative astigmatism, and IOL centration were recorded. Mean follow-up was 12 months +/- 3 (SD).

RESULTS

One day postoperatively, 94% of best cases (n = 46) achieved a BCVA of 20/40 or better and 54%, 20/25 or better. At 2 weeks, 98% had 20/40 or better and 78%, 20/25 or better. After 6 months, all patients achieved a BCVA of 20/40 or better and 83%, 20/25 or better. No statistically significant changes in keratometric astigmatism or IOP occurred.

CONCLUSIONS

The ACR360 IOL gave clinical results comparable to those of other foldable lenses; however, it can also be implanted in cases of intraoperative capsular complications and in eyes with intravitreal silicone oil. Development of an injecting system for implantation and substituting the polypropylene loops with poly(methyl methacrylate) haptics could improve lens quality.

Preliminary results with a new hydrogel intraocular lens

The merits of hydrogel as an intraocular lens material are that it is soft, foldable, hydrophilic, autoclavable and more biocompatible than polymethylmethacrylate (PMMA). Twenty eyes were implanted with a new hydrogel design after phacoemulsification. Fifty per cent achieved a corrected acuity of 6/5 and all achieved 6/9 with correction. Results confirmed an excellent biocompatibility of the material but two cases of asymptomatic decentration indicated the occasional instability within the capsular sac. For best results the hydrogel requires an intact capsulorrhexis with a diameter between 4.5 and 5.0 mm.