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Preliminary results of cataract extraction with implantation of a single-piece AcrySof intraocular lens

Caporossi, Aldo MD*,a; Casprini, Fabrizio MDa; Tosi, Gian Marco MDa; Baiocchi, Stefano MDa

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Journal of Cataract & Refractive Surgery: April 2002 - Volume 28 - Issue 4 - p 652-655
doi: 10.1016/S0886-3350(01)01121-X
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Abstract

Since its introduction in 1994, the AcrySof® acrylic intraocular lens (IOL) (Alcon Surgical) has assumed a prominent role in cataract surgery. AcrySof quickly became the preferred IOL optic material of many cataract surgeons.

The MA30BA, the most widely used AcrySof model, is a foldable posterior chamber IOL with truncated hydrophobic optics and poly(methyl methacrylate) (PMMA) haptics. The MA30BA has several advantages over PMMA and silicone IOLs including a decreased incidence of posterior capsule opacification (PCO) and the consequent reduced need for neodymium:YAG (Nd:YAG) laser capsulotomy1,2 and lower inflammatory reaction on the IOL surface.3 The optic geometry of the AcrySof IOL,3,4 its good biocompatibility,5,6 and its strong adhesion to the posterior capsule5,7 are important factors in preventing PCO.

The AcrySof SA30AL IOL was introduced to increase the IOL's biocompatibility and reduce PCO. This study comprised 20 patients who had phacoemulsification and implantation of the AcrySof SA30AL IOL.

Patients and Methods

This single-center prospective study at the Department of Ophthalmology and Neurosurgery of the University of Siena comprised 20 eyes of 20 patients who had cataract surgery and implantation of an AcrySof SA30AL IOL between March and April 2000 by the same surgeon (A.C.). The mean age of the patients was 69.5 years (range 61 to 78 years). No patient had systemic or ocular disease (eg, diabetic retinopathy, age-related macular degeneration, glaucoma) that would interfere with postoperative visual acuity. Patients with nuclear cataract were selected so a fully dilated fundus examination could be performed in all eyes.

The AcrySof SA30AL (Figure 1) is a foldable, single-piece IOL with optic and haptics of phenylethyl acrylate and phenylethyl methacrylate copolymer cross linked with butanediol acrylate, a material with good residual memory. The refractive index is 1.55. The diameter of the biconvex optic is 5.5 mm and the overall length, 12.5 mm. The lens has a smooth surface and a sharp edge. The haptics have a modified L design and an angulation of 0 degrees (Figure 2).

Figure 1.
Figure 1.:
(Caporossi) The AcrySof SA30AL lens.
Figure 2.
Figure 2.:
(Caporossi) The optic edge and haptic of the AcrySof SA30AL lens create a path for cells to proliferate as they travel from the equatorial capsule.

Surgery was performed using local anesthesia comprising a peribulbar injection of lidocaine and bupivacaine. After a 3.2 mm wide, self sealing, short corneal tunnel with a 3.2 shelving keratotomy was created, sodium hyaluronate (Biolon®) was used to reform and stabilize the surgical planes and protect the corneal endothelium. A 4.00 to 5.25 mm continuous curvilinear capsulorhexis was made with a Caporossi forceps, and the nucleus was removed by divide-and-conquer phacoemulsification using an Alcon Legacy machine. The posterior capsule was polished as necessary. For insertion, the lens was folded longitudinally with a Universal Caporossi folder and holder. The leading haptic was inserted in the capsular bag through the enlarged 3.2 mm wound. The scleral wound was not sutured.

Follow-up visits were at 1 day, 1 week, and 3, 6, and 8 months. The main outcome measures were control of IOL folding, ease of IOL implantation, IOL centration, intraoperative and postoperative complications, visual acuity, and the incidence of PCO and anterior capsule opacification (ACO). Lens centration and opacification were evaluated by retroillumination with slitlamp microscopy.

Results

In all cases, the AcrySof SA30AL IOL showed good flexibility and thus required minimal compression during folding and implantation. The strength and memory of the haptics were excellent, and the unfolding was controlled and rapid.

No intraoperative complications were observed. Postoperatively, there was no haze, IOL discoloration, or inflammatory cell deposits on the IOL surface. The IOL was well centered in all cases at every follow-up.

The mean preoperative best corrected visual acuity was 20/60 (range 20/80 to 20/40). One week after surgery, it was 20/40 in 2 patients, 20/30 in 5 patients, 20/25 in 8 patients, and 20/20 in 5 patients.

No eye developed ACO or phimosis. At 6 months, 1 eye had a well-demarcated, 1.7 mm diameter oval area of lens epithelial cell (LEC) proliferation on the posterior capsule far from the visual axis that did not affect visual acuity (Figure 3).

Figure 3.
Figure 3.:
(Caporossi) A 1.7 mm area of LEC proliferation on the posterior capsule in 1 patient did not involve the visual axis.

Discussion

The AcrySof SA30AL IOL was easily and safely implanted in the capsular bag through a 3.2 mm incision in all cases. The strength and memory of the haptics were excellent, allowing the IOL to be folded during implantation with no damage. Because the IOL is so flexible, minimal compression is required to fold it for implantation and the unfolding is well controlled and rapid. The haptic shape probably contributes to the lens' stability in the capsular bag and to the absence of IOL tilting and decentration. Moreover, because of the single-piece design, the compression force is low and the compression force decay remains stable. This is in contrast to poly(methyl methacrylate) (PMMA) haptics, which require higher compression forces that rapidly diminish (Figure 3). The low but stable compression force decay of the AcrySof SA30AL increases stabilization of the lens in the capsular bag as a result of anterior and posterior capsule adherence. This leads to a lower incidence of posterior capsule folds and PCO than with PMMA haptics.

Figure 4.
Figure 4.:
(Caporossi) Comparison of haptic compression force decay between a multipiece PMMA IOL (12.5 and 13.0 mm) and the single-piece AcrySof SA30AL (12.5 mm) (10.0 mm diameter, water @ 35°C ± 2°C).

As expected, there were no cases of ACO or phimosis. We were, however, surprised to find a well-demarcated oval area of LEC proliferation on the posterior capsule in 1 patient 6 months after surgery; an examination 2 months later found the area unchanged.

Hollick et al.8 report that the rate of PCO and Nd:YAG laser capsulotomy is significantly lower with the AcrySof lens than with PMMA and silicone IOLs. It has been postulated that this difference could be the result of lens material biocompatibility and edge design and the strong adhesion to the posterior capsule of the AcrySof optic. Nishi and Nishi3 found no difference in the prevention of LEC migration between AcrySof and PMMA IOLs with similar sharp-edged optic designs, suggesting the importance of IOL design in preventing PCO.

In an experimental animal model study, Yoon and coauthors9 found that the combined use of an IOL and intracapsular ring or an intracapsular ring alone led to less PCO than extracapsular cataract extraction only. This suggests that the IOL haptic design may have a role in preventing PCO by maintaining posterior capsule tension and forming a mechanical barrier to the lens epithelium.

The AcrySof SA30AL IOL haptic design should be evaluated as a possible cause of the LEC proliferation onto the posterior capsule in 1 of our patients. We believe the haptic width should be increased to balance the high flexibility of the haptic material, which could reduce IOL stability in the capsular bag. The wide haptic width may prevent the anterior capsule from touching the posterior capsule, forming a path for LEC proliferation. Another possible explanation is that a small residual plaque of LECs proliferated, forming an oval area of opacification on the posterior capsule. Two months after the PCO was detected in our patient, the area had not enlarged. However, we cannot exclude the possibility of this happening later.

In conclusion, preliminary results indicate that the AcrySof SA30AL IOL is effective, safe, and easily manipulated. However, to draw conclusions, numerous series of cases with a prolonged follow-up must be evaluated. Significantly more data and time are needed to verify the incidence of LEC proliferation onto the posterior capsule.

References

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2. Hayashi H, Hayashi K, Nakao F, Hayashi F. Quantitative comparison of posterior capsule opacification after polymethylmethacrylate, silicone and soft acrylic intraocular lens implantation. Arch Ophthalmol 1998; 116:1579-1582
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9. Yoon YD, Lim SJ, Kim HB. The effect of the haptic portion of intraocular lens on the development of posterior capsule opacification in rabbit. Yonsei Med J 1999; 40:232-237
© 2002 by Lippincott Williams & Wilkins, Inc.