Assessment of Postoperative Vision and Cylinder Correction

For years, surgeons waited for a multifocal toric IOL to come to market. Although outcomes with multifocal IOLs were excellent, there was still the potential for residual astigmatism to reduce postoperative UCVA and for patients to require secondary enhancements. Surgeons had to use other methods, such as limbal relaxing incisions, to treat patients who presented with more than 0.75 to 1.00 D of preexisting astigmatism. A toric multifocal IOL, cataract surgeons reasoned, would assist in the quest to provide patients with accurate astigmatic and refractive correction at the time of surgery, especially for high levels of astigmatism.

With several models of multifocal toric IOLs now available, surgeons have reported good postoperative outcomes.^1-6 We recently participated in the largest study of a diffractive multifocal toric IOL to date, and our results confirm those of previous investigations.⁶

MULTICENTER STUDY

The AT LISA multifocal toric 909M IOL (Carl Zeiss Meditec) is positioned in the capsular bag by aligning two linear reference marks on the optic with the corneal steep meridian. On the anterior surface of the IOL are the aspheric and toric components, and on the posterior surface the diffractive component; the design provides a near add of 3.75 D at the IOL plane.

We participated in a multicenter observational study designed to confirm the safety, reliability, and efficacy of the AT LISA multifocal toric IOL. Our primary aim was to evaluate visual outcomes and cylinder correction in astigmatic patients; secondary aims included evaluation of IOL stability, postoperative misalignment, depth of field, and contrast sensitivity.

All 148 patients included in the study had bilateral cataract, regular astigmatism, a desire for spectacle independence, and an expected visual acuity of 0.5 logMAR or better. Patients older than 75 years and those with known amblyopia, previous ocular surgery, ocular disease, corneal thickness less than 500 μm, and endothelial cell density of 1,200 cells/mm² or less were excluded.

All eyes had normal intraocular pressure (IOP; mean, 14.9 ±3.5 mm Hg), and 24.6% of patients reported the presence of glare under bright light or with light spots. Under photopic conditions, mean pupil diameter was 3.6 ±0.9 mm; under mesopic conditions, it was 4.7 ±1.1 mm. Preoperatively, mean distance UCVA was 0.7 ±0.5 log- MAR, mean distance BCVA was 0.2 ±0.3 logMAR, mean near UCVA was 0.7 ±0.4 logMAR, and mean distance-corrected near BCVA was 0.3 ±0.3 logMAR. Table 1 includes preoperative refraction, keratometry, and biometry information.

SURGICAL TECHNIQUE

Preoperatively, the horizontal and steepest corneal meridians were marked with the patient in a seated position. Intraoperatively, the surgeon made the main incision in his or her preferred location (clear cornea [n=9], near clear cornea [n=8], scleral tunnel [n=3]) and performed the capsulorrhexis (mean size, 5.5 ±0.5 mm). The mean incision length was 2.1 ±0.3 mm intraoperatively and 2.2 ±0.3 mm immediately postoperatively. The phacoemulsification technique was of the surgeon’s preference. Capsular polishing was performed in 87% of eyes.

All IOLs were implanted with an AT.Shooter A2-20000/ ACM2 or an A6/AT.Smart Cartridge Set single-use injector (both by Carl Zeiss Meditec) and rotated into place by aligning the reference marks located on the IOL with the corneal marks at the steepest meridian. The four-haptic design of the IOL allows both clockwise and counterclockwise rotation of the lens, and this aided in orienting and rotating the lens into its final position. Proper orientation was confirmed after removal of the ophthalmic viscosurgical device.

EVALUATION AND RESULTS

In order to be included in the evaluation, microincision cataract surgery had to be uneventful, and the IOL had to be located in the capsular bag with 360º overlap of the capsulorrhexis edge by the IOL. In total, 142 patients (284 eyes) were included in the statistical analysis; two patients who received a nontoric IOL in their second eye and four patients who had operative reports for one eye only were excluded.

Patients were examined within the first postoperative week for safety, including evidence of IOL rotation, and for monocular visual acuity. In examinations at 30 to 60 days, 90 to 120 days, and 180 to 210 days, they were evaluated for safety and for subjective and objective refractions, monocular and binocular distance and near visual acuities, pupil diameter, corneal topography, and contrast sensitivity. Additionally, a binocular defocus curve was obtained at the 90- to 120-day visit.

Distance vision. Because eyes with suboptimal potential visual acuity were included in this study, postoperative distance UCVA and BCVA were slightly lower than has been seen in similar studies with diffractive multifocal IOLs.^7-12 At 1 month, 48% of eyes achieved a distance UCVA of 0.1 logMAR or better and 85% of 0.3 logMAR or better. These results were stable through 6-month follow-up. The monocular distance BCVA was 0.3 logMAR or better in all eyes, and 87% achieved 0.1 logMAR or better (Table 2). A comparison of distance BCVA and UCVA revealed a difference of 4 to 5 letters, which is consistent with the refractive outcomes.

Our results showed that the improvements in distance visual acuity from preoperative levels (mean, 0.7 ±0.5 logMAR) confirm that the AT LISA multifocal toric IOL effectively restores distance vision.

Near vision. At 1 week postoperative, mean near visual acuity improved from preoperative levels; it improved again from 1 week to 1 month. Thereafter, near visual acuity remained relatively stable. At 1 month, 80.9% of eyes achieved a near UCVA of 0.30 logMAR or better and 40.4% achieved 0.10 logMAR or better. Regarding distance-corrected near BCVA, from 1 to 6 months postoperatively, 91% of eyes achieved 0.30 logMAR or better. Additionally, 57% and 68.3% of eyes achieved a distance-corrected near BCVA of 0.10 logMAR or better at 1 and 6 months, respectively. The binocular distance-corrected near BCVA was the same as the monocular near BCVA (Table 3). Postoperatively, no patient reported the use of reading glasses at any time in the study, but 6% reported experiencing visual disturbances while reading a book.

Intermediate vision. At 60 and 80 cm (intermediate vision), visual acuity was 0.22 logMAR or better in all eyes at every postoperative visit. These results were similar with and without distance correction. Without correction, intermediate visual acuity was always better than 0.23 logMAR and 0.15 logMAR at 60 and 80 cm, respectively.

Sphere and cylinder. The results of our study showed a clear shift in the subjective refraction toward emmetropia. Eyes treated early in the study had a tendency toward slight hyperopia after surgery; this was remedied by refining the IOL power calculation. By the 6-month visit, 89.2% of eyes were within ±1.00 D of emmetropia. We also found a decrease in subjective cylinder values from baseline to the 180-to- 210-day visit. The subjective astigmatism at this interval was less than 1.00 D in 80.6% of eyes and less than 0.50 D in 47.1%.

Correction of preoperative astigmatism remained stable from the first postoperative visit, and only three eyes experienced no change in their astigmatism level from pre- to postoperative. Some overcorrection did take place, as confirmed by vector analysis of target-induced and surgically induced astigmatisms and the difference vector.

Defocus curve. To obtain the defocus curve from the 90-to-120-day visits, we calculated the depth of field as the dioptric interval that provided patients with a visual acuity of at least 0.24 logMAR. This interval was 4.82 ±1.25 D. The binocular defocus curve contained two peaks, at 0.00 and -2.50 D, and limited loss of vision within the interval.

Contrast sensitivity. Under photopic conditions, the values for binocular contrast sensitivity were similar at the 30-to-60-, 90-to-120-, and 180-to-210-day visits. Results under photopic conditions at 1.5 and 3.0 cycles per degree (cpd) were equal to those obtained under mesopic conditions; at 6, 12, and 18 cpd they were lower by 0.2 log units.

Rotational stability. The mean rotation of the AT LISA multifocal toric IOL was 1.46 ±8.93º. Nearly all IOLs (95.9%) had rotated 5º or less by the 90-to-120-day visit, and 89.8% showed no signs of rotation. Only 3.2% of IOLs rotated more than 5º. Of significance, rotational results remained stable until the 180-to-210-day visit, the point at which the process of capsular bag healing is typically finished.

Safety. Laser capsulotomy was performed to treat posterior capsular opacification at 30 to 60 days (n=8), 90 to 120 days (n=13), and 180 to 210 days (n=19). In these patients, data from after laser treatment were included in the analysis.

No change in IOP was noted at any time, and IOP was normal at the 1-to-7-day visit. Pupil diameter did not change from baseline to the 180-to-210-day visit. Under mesopic and photopic conditions at that visit, mean pupil diameter was 4.64 ±0.95 and 3.42 ±0.87 mm, respectively, compared with baseline levels of 4.78 ±0.99 and 3.49 ±0.86 mm, respectively.

Adverse events included a fibrinous reaction lasting less than 1 week in one eye and transient macular edema in one eye. In three cases, the AT LISA multifocal toric IOL was explanted, two due to unacceptable residual refractive errors and one due to a damaged IOL. Additionally, two IOLs that were off-axis were repositioned postoperatively.

CONCLUSION

In our study, the mean subjective cylinder decreased from -2.39 ±1.48 D preoperatively to -0.49 ±0.53 D at the 180-to-210-day visit, confirming that the AT LISA multifocal toric IOL can accurately correct corneal astigmatism in a wide range of diopters. Published studies of spherical diffractive multifocal IOLs have shown similar postoperative astigmatism values in eyes with less than 1.00 D of astigmatism preoperatively.^7-12

Considering that, for multifocal diffractive IOLs, 1.00 D has been deemed an acceptable level of postoperative cylinder,^13,14 the results of our study are promising, as this level was easily surpassed. Also promising is that all of our patients not only were satisfied but also did not require glasses for distance or near vision after lens implantation. Additionally, about half of the eyes had less than 0.50 D of refractive astigmatism, which we consider to be a perfect outcome.

Given that this study was the largest series of eyes to date implanted with a diffractive multifocal toric IOL, and that good distance and near UCVA and sphere and cylinder correction were achieved, we believe that the AT LISA multifocal toric IOL can effectively and safely be used for the correction of any degree of preoperative astigmatism.

Sheraz M. Daya, MD, FACP, FACS, FRCS(Ed), FRCOphth, is Director and Consultant of Centre for Sight, East Grinstead, United Kingdom. Dr. Daya is a Chief Medical Editor of CRST Europe. He states that he is a consultant to Carl Zeiss Meditec. He may be reached at e-mail: sdaya@centreforsight.com.

Roberto Bellucci, MD, is Chief of the Ophthalmic Unit, Hospital and University of Verona, Italy. Dr. Bellucci states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: robbell@tin.it.

1. Ferreira TB, Marques EF, Rodrigues A, Montés-Micó R. Visual and optical outcomes of a diffractive multifocal toric intraocular lens. J Cataract Refract Surg. 2013;39(7):1029-1035.
2. Visser N, Nuijts RM, de Vries NE, Bauer NJ. Visual outcomes and patient satisfaction after cataract surgery with toric multifocal intraocular lens implantation. J Cataract Refract Surg. 2011;37(11):2034-2042.
3. Venter J, Pelouskova M. Outcomes and complications of a multifocal toric intraocular lens with a surface-embedded near section. J Cataract Refract Surg. 2013;39(6):859-866.
4. Khoramnia R, Auffarth GU, Rabsilber TM, Holzer MP. Implantation of a multifocal toric intraocular lens with a surface-embedded near segment after repeated LASIK treatments. J Cataract Refract Surg. 2012;38(11):2049-2052.
5. Rabsilber TM, Kretz FT, Holzer MP, Fitting A, Sanchez MJ, Auffarth GU. Bilateral implantation of toric multifocal additive intraocular lenses in pseudophakic eyes. J Cataract Refract Surg. 2012;38(8):1495-1498.
6. Bellucci R, Bauer NJ, Daya SM, et al, for the Lisa Toric Study Group. Visual acuity and refraction with a diffractive multifocal toric intraocular lens. J Cataract Refract Surg. 2013;39(10):1507-1518.
7. Alió JL, Piñero DP, Plaza Puche AB, et al. Visual and optical performance with two different diffractive multifocal intraocular lenses compared to a monofocal lens. J Refract Surg. 2011;27:570-581.
8. Can I, Bostancı Ceran B, Soyugelen G, Takmaz T. Comparison of clinical outcomes with 2 small-incision diffractive multifocal intraocular lenses. J Cataract Refract Surg. 2012;38:60-67.
9. Akaishi L, Vaz R, Vilella G, Garcez RC, Tzelikis PF. Visual performance of Tecnis ZM900 diffractive multifocal IOL after 2500 implants: a 3-year follow-up. J Ophthalmol. 2010;2010.
10. Souza CE, Muccioli C, Soriano ES, et al. Visual performance of AcrySof ReSTOR apodized diffractive IOL: a prospective comparative trial. Am J Ophthalmol. 2006;141:827-832.
11. Gil MA, Varon C, Rosello N, Cardona G, Buil JA. Visual acuity, contrast sensitivity, subjective quality of vision, and quality of life with 4 different multifocal IOLs. Eur J Ophthalmol. 2012;22:175-178.
12. Kohnen T, Allen D, Boureau C, et al. European multicenter study of the AcrySof ReSTOR apodized diffractive intraocular lens. Ophthalmology. 2006;113:578-584.
13. Hayashi K, Manabe S, Yoshida M, Hayashi H. Effect of astigmatism on visual acuity in eyes with diffractive multifocal intraocular lens. J Cataract Refract Surg. 2010;36:1323-1329.
14. de Vries NE, Webers CA, Touwslager WR, et al. Dissatisfaction after implantation of multifocal intraocular lenses. J Cataract Refract Surg. 2011;37:859-865.