Surface Alterations on PMMA-Intraocular Lenses Induced by Different Implantation Forceps

Acrylic intraocular lens damage after folding using a forceps insertion technique

PURPOSE

To analyze intraocular lens (IOL) surface abnormalities seen after folding using a forceps insertion technique.

SETTING

Mayo Clinic, Rochester, Minnesota, USA.

METHODS

Acrylic AcrySof MA60AC IOLs were examined using an Axio Imager microscope before and after they were folded using a forceps insertion technique. Differential interference contrast, brightfield reflected light, and darkfield reflected light imaging techniques were used as necessary. The effects of temperature, time, and ophthalmic viscosurgical device (OVD) on optic surface abnormalities after folding were studied.

RESULTS

All 17 IOLs examined had smooth, defect-free optic surfaces before folding. After folding, anterior optic surface depressions were observed in all IOLs; the depressions corresponded to the contact area of the titanium insertion forceps. Surface depressions were present up to 72 hours after folding, were more pronounced when an insertion forceps with a high degree of wear was used, and were greater when the IOL was warmed to 98 degrees F before folding. Coating the IOL surface with OVD before grasping it with the insertion forceps prevented formation of depressions.

CONCLUSIONS

The anterior optic surface of the acrylic IOL was vulnerable to forceps-induced surface depressions. Surface abnormalities were prevented by coating the anterior optic surface with OVD before grasping it with a metal insertion forceps.

Edge profile of commercially available square-edged intraocular lenses

PURPOSE

To analyze the sharpness of the posterior optic edge profile and edge thickness of intraocular lenses (IOLs) marketed with a square-edged profile.

SETTING

Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.

METHODS

Seventeen square-edged 20.0 diopter IOLs of different manufacture, design, and material were selected. After the environmental scanning electron microscopy technique was standardized, repeatability of the technique was tested. Posterior optic edges of all IOLs were scanned at a magnification of x 500. Local radii of curvature of the posterior optic edges were measured by purpose-designed software. Optic edge thickness was also measured from the electron micrographs.

RESULTS

The repeatability of the scanning technique was excellent (+/-0.10 microm). The radius of curvature of posterior optic edges ranged from 7.6 to 23.1 microm. Hydrophilic acrylic IOLs (except the HumanOptics MC Microlens 611 MI-B and 1CU) had radii of curvatures more than 10.0 microm of the posterior optic edge compared with hydrophobic acrylic and silicone IOLs (<10.0 microm) except the Hoya AF-1 (19.9 microm). Alcon AcrySof single-piece (SN60WF), HumanOptics 1CU, and AMO Clariflex CLRFLXC IOLs had the thinnest optic edges in the hydrophobic, hydrophilic, and silicone groups, respectively.

CONCLUSIONS

Commercially marketed square-edged IOLs differed in the sharpness of the posterior optic edge. Hydrophobic acrylic and silicone IOLs have sharper posterior optic square edge than most hydrophilic acrylic IOLs. This probably reflects difference in manufacturing techniques. Differences in posterior optic edge profile may explain variation in posterior capsule opacification performance with different IOLs and materials.

Scanning electron microscopic characteristics of phakic intraocular lenses

OBJECTIVE

To analyze the surface quality of new generation phakic intraocular lenses (IOLs).

DESIGN

Experimental materials study.

MATERIALS

Three different new generation phakic IOLs: angle-fixated anterior chamber lens Chiron Vision NuVita MA20 (polymethylmethacrylate [PMMAD, iris-fixated anterior chamber lens Ophtec Artisan Iris-Claw (PMMA), posterior chamber lens Staar ICM (polymer from porcine collagen and 2-hydroxyethyl methacrylate [HEMA]).

METHODS

Representative samples of three different phakic IOLs underwent surface and edge-finish examination with light microscopy (LM). The phakic IOLs were then examined by use of scanning electron microscopy (SEM), and particular attention was given to optic surface quality, edge finish, haptic, and optic/haptic junction.

RESULTS

In all IOLs the LM examination showed a smooth and homogeneous surface. No irregularities, particularly at the optic front and back surface, optic edge, haptic, and the optic/haptic junctions, were detected by SEM. One exception was a minor surface roughness at the claws of an Artisan iris-fixated anterior chamber IOL.

CONCLUSIONS

Phakic IOLs are implanted either in the anterior or posterior chamber of healthy eyes, and high standards for their surface quality are required. The evaluation of surface properties with LM and SEM did not reveal any defects that contraindicate the implantation of phakic IOLs.

Effect of folding on the multifocal silicone intraocular lens: scanning electron microscopic study

PURPOSE

To evaluate whether the surface of the refractive zonal multifocal silicone intraocular lens (IOL) is altered by different folding and implantation instruments and is more sensitive to manipulation during folding than the surface of a monofocal IOL.

SETTING

Department of Ophthalmology, University Hospital, Kiel, Germany.

METHODS

Evaluated were the refractive multifocal silicone IOL (SA-40N, Array) and an otherwise identical monofocal IOL (SI-40NB) from the same manufacturer (Allergan Inc.). Different folding devices (folding blocks, folding and implantation forceps, and an injector system) were used. The IOLs were kept folded for 60 seconds; 24 hours later, scanning electron microscopy (SEM) was performed. In addition, the cartridges of the injector system were examined by SEM.

RESULTS

Overall, regardless of the folding and implantation instruments used, both the multifocal and monofocal IOLs had discrete surface alterations. The cartridges of the injector system had a rough surface at the tip, while the proximal portion appeared smooth.

CONCLUSION

There were no signs of lesions particularly affecting the surface of multifocal IOLs.

Silicone-covered forceps for rigid intraocular lens implantation

Metal implantation forceps can damage the surface of poly(methyl methacrylate) and heparin-surface-modified intraocular lenses (IOLs) during insertion. A new implantation forceps with silicone sleeves covering the tips has been successfully used during IOL implantation. Scanning electron microscopic studies showed that the silicone sleeves prevent forceps-induced IOL surface defects.

Scanning electron microscopic analysis of foldable acrylic and hydrogel intraocular lenses

OBJECTIVE

To analyze the surface quality of foldable acrylic and hydrogel intraocular lenses (IOLs).

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, and Institute of Anatomy and Cellular Biology, University of Giessen, Germany.

METHODS

We studied eight foldable IOL models with optics made of six different acrylate/methacrylate polymers: Acrylens ACR360 (loptex), AcrySof MA60BM (Alcon), MemoryLens U940A (Mentor), 92S and 92C (Morcher), Hydroview H60M (Storz), HydroSof SH30BC (Alcon), and ISH66 (Corneal). Four IOLs of each design were examined. Light and scanning electron microscopy were performed before and after IOL folding with forceps.

RESULTS

All IOL models had excellent optic and haptic surfaces. The haptic-optic junctions revealed minimal empty spaces or irregularities in three of the five three-piece IOLs and smooth surfaces in all one-piece IOLs. Minimal surface alterations and superficial defects caused by folding were detectable in the two acrylate (acrylic) IOLs (loptex ACR360, Alcon MA60BM) with low water content.

CONCLUSION

Intraocular lenses of acrylate/methacrylate polymers had excellent surface quality. The acrylic IOLs were vulnerable to mild folding or forceps defects; however, these were less marked than those previously noted with poly(methyl methacrylate) IOLs.