From Associated Eye Care, Stillwater, Minn (Lane); TLC Eye Care of Michigan, Jackson, Mich (Ernest); Jules Stein Eye Institute and the Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, Calif (Miller); and Alcon Laboratories Inc, Ft Worth, Tex (Hileman, Harris, Waycaster).
This study was sponsored by Alcon Laboratories Inc, Ft Worth, Tex. Drs Hileman and Waycaster and Mr Harris are employees of Alcon Laboratories Inc. Drs Lane, Ernest, and Miller were study investigators and consultants to Alcon Laboratories Inc.
Portions of this report were presented previously (Lane SS. The AcrySof Toric IOL’s FDA trial results: a look at the clinical data. Cataract and Refractive Surgery Today. 2006;5:66–68).
Study concept and design (S.S.L., K.S.H., B.H.); data collection (S.S.L., P.E., K.M.M., K.S.H., B.H., C.R.W.); interpretation and analysis of data (S.S.L., P.E., K.S.H., C.R.W.); drafting of the manuscript (S.S.L., K.S.H., C.R.W.); critical revision of the manuscript (S.S.L., P.E., K.M.M., K.S.H., B.H., C.R.W.); statistical expertise (C.R.W.); obtained funding (K.S.H.); administrative, technical, or material support (K.M.M., K.S.H., B.H., C.R.W.); supervision (S.S.L., P.E.)
Correspondence: Stephen S. Lane, MD, Associated Eye Care, 2950 Curve Crest Blvd W, Stillwater, MN 55082. Tel: 651.275.3000; Fax: 651.275.3099; E-mail: email@example.com
Recent advances in cataract surgery techniques and intraocular lens (IOL) technology have led to the development of astigmatism-correcting toric IOLs. The success of early toric IOL models has been limited by rotational instability. Significant rotation degrades the corrective power of the IOL and has been reported in 16% to 25% of cases.1–4 Thus, a high degree of rotational stability is now an essential feature in toric IOLs.
The single-piece, acrylic AcrySof toric IOL (Alcon Laboratories Inc, Ft Worth, Tex) provides spherical and astigmatic correction. Its unique haptic design and bioadhesive characteristics improve adhesion of the IOL to the capsular bag,5,6 enhancing lens stability.
A randomized, patient-masked, parallel-group, multi-center, 1-year study compared the efficacy and safety of the AcrySof toric IOL and an AcrySof spherical control IOL. The AcrySof toric IOL demonstrated favorable efficacy, rotational stability, safety, and distance spectacle freedom in 517 patients with corneal astigmatism. The unilateral results of all 517 patients are pending publication (unpublished data 2009). Following US Food and Drug Administration and institutional review board approval to allow bilateral implantation, patients who participated in the larger study and who required fellow-eye cataract surgery were offered the option of fellow-eye implantation with the same IOL. This report focuses on the results of this substudy.
Patients and Methods
All patients provided informed consent and the study protocol was approved by the applicable institutional review board. Eligible patients were adults of either gender who had at least 0.75 diopter (D) preoperative with-the-rule or oblique regular corneal astigmatism or at least 1.00 D of preoperative against-the-rule regular corneal astigmatism, a dilated pupil diameter ≥6.0 mm, and need of spherical correction between 12.00 and 25.00 D. Patients with irregular corneal astigmatism, keratopathy, or corneal edema were excluded.
The AcrySof toric IOL and the AcrySof spherical control IOL are made from a cross-linked, soft, acrylic polymer with a chemically bonded ultraviolet absorber. Both have single-piece construction, a 6.0-mm optic diameter, asymmetrical biconvex optics, and an overall length of 13.0 mm. The haptics have no angulation and are made of the same acrylic material as the optic. The toric IOL has a toric component on the posterior surface of the optic, which is marked with indentations near the haptic/optic junction representing the flat meridian of the IOL. The spherical control IOL is identical, except it does not have a toric component or markings.
Surgical procedures were consistent with standard practice for the spherical control IOL. For the toric IOL, reference marks were made on the limbus of the operative eye before surgery (eg, 0°, 90°, and 180°), with the patient seated upright to compensate for cyclorotation. After temporal incision (left eye, 0±15°; right eye, 180±15°), the anterior capsule was opened with a continuous-tear capsulorrhexis (4.5- to 5.5-mm diameter). After phacoemulsification and cortical clean up, an axis marking was made at the limbus indicating the implantation axis determined by using manufacturer-provided software (toric calculator, Alcon Laboratories Inc). The lens was folded and inserted into the capsular bag using the Monarch II IOL delivery system and B cartridge (Alcon Laboratories Inc). Next, the IOL was rotated until the IOL axis-marking indentations were aligned with the patient’s lens placement limbus reference marks. Ophthalmic viscoelastic device (OVD) was thoroughly removed while avoiding IOL rotation. Fine realignment of the IOL was performed following OVD removal if needed. Intraocular lens alignment was confirmed before wound closure. No limbal relaxing incisions were made as part of the surgical treatment.
Six-month evaluations included distance uncorrected (UCVA) and best distance spectacle-corrected visual acuity (BSCVA) (assessed with an Early Treatment Diabetic Retinopathy Study [ETDRS] chart), tonometry, slit-lamp microscopy, and a patient satisfaction questionnaire. Statistical analysis was performed using the Cochran-Mantel-Haenszel test with rank scores or two-sample independent t tests.
Sixty-two patients (n=40, toric IOL; n=22, spherical control IOL) opted to undergo implantation in their fellow eye of the same lens they initially received and attended 6-month follow-up. Average age and gender were similar between groups: age: 69.1±11.9 years (toric IOL) and 74.5±9.2 years (spherical control IOL); male gender: 55.6% (toric IOL), 41.7% (spherical control IOL). The majority of patients in both groups were Caucasian. All corneal incisions were temporal, with final mean incision sizes of 3.0 mm for the toric IOL and 3.1 mm for the spherical control IOL
Spectacle independence was greater for the toric IOL group (Fig 1). Ninety-seven percent of patients with toric IOLs reported they had not used spectacles for distance vision in the past month compared with 50% of those with spherical control IOLs. More than twice as many patients with toric IOLs did not require prescription glasses for near or distance than those with spherical control IOLs (75.7% vs 36.3%, P=.0190). The percentage of patients who required prescription spectacles of any type (bifocals, distance, or reading) was 24.3% in patients with toric IOLs but was 63.7% for those with spherical control IOLs.
Figure 1. Distance Spectacle Wear 6 Months After Surgery. Data Were not Available for Three Patients with AcrySof Toric IOLs.
Patients who received bilateral toric IOLs had significantly less absolute residual refractive cylinder than those with bilateral spherical control IOLs (Fig 2). A greater proportion of patients with toric IOLs (60.0%) achieved a residual cylinder between 0.00 and 0.50 D in the second operative eye compared with 22.7% of patients with spherical control IOLs.
Figure 2. Absolute Residual Refractive Cylinder at the Spectacle Plane 6 Months After Surgery.
The improvements in residual refractive cylinder were reflected in the visual acuity results. Patients with toric IOLs had significantly better binocular distance UCVA than those with control IOLs. On average, patients with toric IOLs had one line better (ETDRS chart) binocular distance UCVA than patients with spherical control IOLs (P=.0014) (Fig 3). As expected, distance BSCVA was similar between groups.
Figure 3. Binocular Distance Uncorrected Visual Acuity (UCVA) and Best Spectacle-Corrected Visual Acuity (BSCVA) 6 Months After Surgery. Data Were not Available for Two Patients with Acrysof Toric IOLs.
Almost all patients in both groups were either satisfied or very satisfied with their uncorrected distance vision, whether at night, during the day, or indoors. A larger proportion of patients with bilateral toric IOLs reported being very satisfied with their uncorrected distance vision, both during the daytime (83.8% vs 64.7%, P=.12) and indoors (86.5% vs 64.7%, P=.07), but both measures failed to reach statistical significance.
This analysis of bilaterally implanted patients from a larger, randomized clinical study comparing the AcrySof toric IOL with the AcrySof spherical control IOL highlights several advantages of the toric IOL. The superior distance UCVA of patients bilaterally implanted with the AcrySof toric IOL demonstrates an important clinical advantage that translates into spectacle independence for distance vision. Furthermore, because most patients who received the AcrySof toric IOL did not need astigmatic-correcting prescription glasses, this IOL may be associated with a lower cost of care. The greater spectacle freedom observed with the AcrySof toric IOL in this study may be attributable to the rotational stability of the lens, improved distance UCVA, and accurate predictability of lens cylinder correction. The improved rotational stability of the AcrySof toric IOL7 represents a significant advantage over earlier toric lenses, which have been plagued with rotational issues.1–4 Furthermore, advances in technology and surgical technique may permit smaller incision sizes than were observed in this study. This study’s findings are particularly relevant as corneal astigmatism is common. In a large prospective study of 2415 cataract surgery patients, 64.4% had corneal astigmatism between 0.25 and 1.25 D and 22.2% had ≥1.50 D corneal astigmatism.8
Findings from this study demonstrate that the AcrySof toric IOL represents an attractive option for patients with cataracts and pre-existing corneal astigmatism, providing them with excellent distance vision and permitting the majority to enjoy the benefits of spectacle freedom for distance vision.
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- Ferrer-Blasco T, Montés-Micó R, Peixoto-de-Matos SC, González-Méijome JM, Cervino A. Prevalence of corneal astigmatism before cataract surgery. J Cataract Refract Surg. 2009;35:70–75. doi:10.1016/j.jcrs.2008.09.027 [CrossRef]