Effect of an aspheric intraocular lens on the ocular wave-front adjusted for pupil size and capsulorhexis size

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1 Effect of an aspheric intraocular lens on the ocular wave-front adjusted for pupil size and capsulorhexis size Alja Crnej, 1 Wolf Buehl, 2 Roman Greslechner, 2 Nino Hirnschall 1,3 and Oliver Findl 1,3 1 Moorfields Eye Hospital NHS Foundation Trust, London, UK 2 Department of Ophthalmology, Medical University of Vienna, Vienna, Austria 3 Department of Ophthalmology, VIROS Vienna Institute for Research in Ocular Surgery (VIROS), a Karl Landsteiner Institute, Vienna, Austria ABSTRACT. Purpose: To compare the ocular wave-front of eyes with silicone Intraocular lens (IOLs) with aspheric and spherical optics after cataract surgery, taking into account the patient s pupil size under reading conditions and after pupil dilatation. Methods: In this institutional prospective, randomized, controlled, patient and examiner masked, bilateral trial with intra-individual comparison, 60 eyes of 30 patients with bilateral age-related cataract were included. Each patient received a spherical IOL (CeeOn Edge, 911A, AMO, Santa Ana, CA, USA) in one eye and an aspheric IOL (Tecnis, Z9000, AMO) in the contra-lateral eye. Exclusion criteria were other ocular pathologies, capsular changes or zonular weakness. The main outcome variable was spherical aberration of the ocular wave-front under mesopic pupil conditions measured 2 years after surgery. Additional outcome variables were visual acuity and photopic and mesopic contrast sensitivity. Results: There was no significant difference in visual acuity between the two IOL types under physiological pupil conditions and also not after pupil dilation. However, spherical aberrations were significantly lower with the aspheric IOL (SA: spherical 0.38 lm, SD: 0.11 lm; aspheric 0.10 lm, SD: 0.13 lm; p < 0.01), and there was a significant difference in contrast sensitivity at 12 cycles/degree. Conclusions: This is the first randomized and masked trial on visual function and ocular wave-front after implantation with this silicone aspheric IOL, taking the patients own pupil size into account. The effect on visual function was detectable for mesopic contrast sensitivity, but there was no difference in visual acuity. The SA was found to be significantly lower under physiological pupil conditions as well as when recalculated for the rhexis size and under pharmacological dilatation. Key words: aspheric intraocular lens pupil size wave-front Acta Ophthalmol. 2014: 92: e353 e357 ª 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd doi: /aos Introduction A goal of cataract surgery today is not only to restore visual acuity but also to provide the best quality of vision possible. The cornea typically induces positive spherical aberration, which in young people is compensated for by the negative spherical aberration of the crystalline lens. As the eye ages, spherical aberration of the lens shifts towards less negative or even positive values (Smith et al. 2001), which when combined with the positive corneal spherical aberration (Glasser & Campbell 1998; Guirao et al. 2002; Packer, Fine & Hoffman 2004), results in an increased total spherical aberration and decreased ocular optical quality (Brunette et al. 2003; He et al. 2003; Montes- Mico, Ferrer-Blasco & Cervino 2009). Intraocular lens (IOL) implantation after cataract surgery provides excellent visual acuity outcomes, but contrast sensitivity in pseudophakic eyes is lower than in normal, elderly presbyopic eyes. Aspheric IOLs with a modified optic geometry induce negative spherical aberration and were designed to compensate for the spherical aberration of the cornea to improve optical performance. The aim of this study was to compare the optical performance of an aspheric IOL with a modified anterior surface to that of a standard spherical IOL of an otherwise similar design. Outcome variables were visual acuity, photopic and mesopic contrast sensitivity as well as measurements of the ocular wave-front. Patients and Methods This prospective randomized singlecentre study was approved by the local ethics committee and adhered to the e353

2 guidelines of the tenets of Declaration of Helsinki. The aspheric IOL (AIOL) (Tecnis Z9000; AMO, Santa Ana, CA, USA) was compared to the spherical IOL (SIOL) (CeeOn Edge 911A, AMO) in this randomized, controlled, doublemasked, bilateral trial with intra-individual comparison. Both IOLs are foldable, three-piece, open-loop silicone IOLs with a 6.0 mm, biconvex optic and square-edge design. The only difference between the IOLs is a modified anterior surface of the optic in the aspheric lens, which has a flatter curvature in the periphery. Thirty patients with bilateral agerelated cataract were included after providing consent. Exclusion criteria consisted of retinal pathology with a likely expected postoperative visual acuity outcome of 0.8 Snellen or worse, as well as any capsular changes that would increase the risk of postoperative decentration or tilt of the IOL, such as pseudoexfoliation syndrome or zonular weakness. The first eye to be operated on was randomly assigned to receive either an AIOL or a SIOL using a sealed-envelope randomization method. The fellow eye received the alternate IOL type and had surgery within the next 2 weeks. Surgery was performed in a standardized way by an experienced surgeon. The surgical technique included application of topical anaesthesia, a 3.0-mm temporal limbal incision, capsulorhexis, phacoemulsification, irrigation/aspiration of cortical remnants and IOL implantation in the capsular bag with an injector. In addition to the regular check-up, a followup examination was performed 2 years postoperatively. At 2 years, the patient s distant corrected visual acuity (DCVA) was determined using the backlit Early Treatment Diabetic Retinopathy Study (ETDRS) chart (Lighthouse International, New York, NY, USA) at 4.0 m with a 100% contrast chart and then with a 5% contrast chart. Under these conditions, pupil size was measured using a Colvard pupillometer (Oasis Medical, Glendora, USA). While measuring pupil size in one eye, the other eye was fixating on the ETDRS chart. To evaluate the effect of the pupil size on visual acuity, the tests were repeated as described above following pharmacological dilatation of the pupil, using phenylephrine 2.5% and tropicamide 0.5%. Contrast sensitivity (CS) was measured using the FACT chart (Ginsburg Box, VSCR-CST-6500; Vision Science Research Corporation, Walnut Creek, CA, USA) under mesopic lighting conditions (6 cd/m²). The FACT chart consists of five rows (A to E) of sinewave gratings with increasing frequency values of 1.5, 3, 6, 12 and 18 cycles/degree and nine columns with decreasing contrast levels. The patient reports the orientation of the gratings: right, up or left. The last correct grating seen for each spatial frequency is plotted on a contrast sensitivity curve. Wave-front aberrations were measured with a Hartmann Shack sensor (WASCA Analyzer; Carl Zeiss Meditec, Jena, Germany) and calculated for three different analysis diameters. All measurements were performed under maximal mydriasis, and the wave-front errors were described according to the OSA (Optical Society of America) notation for Zernike polynomials. At least three measurements were taken per eye, and the mean values of the Zernike coefficients (up to the 5th order) and root mean square (RMS) [of the total and higher order aberrations (HOA s)] were calculated. Concerning the diameter of analysis, Zernike polynomials were recomputed for each patient s individual pupil diameter (natural pupil size) measured during the ETDRS testing, as this was the main outcome measure. The pupil diameter was measured in each eye under visual acuity measurement conditions and then taken as diameter of analysis for the respective wave-front measurement. The Zernike polynomials were also recomputed for the individual rhexis diameters as measured from the retroillumination photograph to investigate the influence of the IOL/ rhexis overlap on the ocular wavefront. Finally, the wave-front was measured under maximal pharmacological pupil dilatation. Although dilated pupil size and rhexis size are not physiological diameters of the pupil, these diameters were included to assess aberration scores under extreme conditions. However, the main outcome measure was determined at physiological pupil size. Slitlamp examination included investigation of the occurrence of capsular folds, IOL decentration, buttonholing (none, partial, half or full), extent of anterior fibrosis (ACO) and posterior capsule opacification (PCO). The PCO intensity was assessed using digital retroilluminated photographs and Automated Quantification of After-Cataract (AQUA) (Findl 2003) software. From the photos taken, rhexis diameter and rhexis area were analysed. For statistical analysis, Microsoft Excel 2011 for Mac (Microsoft, Redmond, WA, USA) with a Statplus:mac version plug-in (AnalystSoft, Alexandria, VA, USA) and a Xlstat 2012 plug-in (Addinsoft, Paris, France) were used. Descriptive data are always shown as mean, standard deviation (SD) and range, if not stated otherwise. A 2-sided paired t-test was used to assess significance in differences between both IOLs in BDVA. P-values < 0.05 were considered statistically significant. Multiple testing with a Bonferroni correction was used to assess difference in contrast sensitivity and wave-front aberrations. The Bonferroni-corrected significance value was Results Thirty patients with bilateral cataracts were recruited for this trial. The average age of the patients was 76.0 years (range: years). Twenty-one patients came for the 2-year examination. Of the nine patients that were lost to follow-up, three were previously excluded due to exclusion criteria, one patient had died, three could not be contacted and two refused to come for the examination. Concerning visual acuity, no significant difference was found between the two IOLs either under natural or pharmacological dilation conditions (Table 1). Distance low-contrast visual acuity with the 5% ETDRS chart showed a trend for better acuity with the AIOL under both pupil size conditions; however, this was not statistically significant (Table 1 and Fig. 1). Average contrast sensitivity under mesopic lighting conditions (6 cd/m²) showed no significant differences between the IOLs (p 1.5 = 0.957; p 3 = 0.520; p 6 = 0.453; p 12 = 0.391; p 18 = 0.789). However, comparing single pairs of each spatial frequency showed a significant difference at 12 cycles per degree (p (Wilcoxon rank test)=0.02) (Fig. 2.) e354

Table 1. Visual acuity (VA) as the number of correctly read letters on the ETDRS chart and distance low-contrast VA with the 5% ETDRS chart.

0 to 68.0) 57.0 (SD: 6.3, from 51.0 to 67.0) 57.1 (SD: 5.7, from 47.0 to 67.0) 44.1 (SD: 6.3, from 34.0 to 53.0) 44.2 (SD: 5.7, from 29.0 to 53.0) 34.2 (SD: 10.1, from 10.0 to 47.0) 37.9 (SD: 7.

Circles ( ) are outliers, asterisks ( ) are extreme values. The mean pupil size under visual acuity testing in dim room light was 4.05 mm (SD: 0.85 mm, range from 3.00 to 6.50 mm) in SIOL group and 4.

3 Table 1. Visual acuity (VA) as the number of correctly read letters on the ETDRS chart and distance low-contrast VA with the 5% ETDRS chart. No significant difference was found between IOLs VA Distance low-contrast VA Pupil size Physiological Dilated Physiological Dilated SIOL 58.9 (SD: 5.5, from 52.0 to 68.0) AIOL 60.6 (SD: 5.2, from 51.0 to 68.0) 57.0 (SD: 6.3, from 51.0 to 67.0) 57.1 (SD: 5.7, from 47.0 to 67.0) 44.1 (SD: 6.3, from 34.0 to 53.0) 44.2 (SD: 5.7, from 29.0 to 53.0) 34.2 (SD: 10.1, from 10.0 to 47.0) 37.9 (SD: 7.3, from 19.0 to 53.0) Fig. 1. Visual acuity under physiological pupil conditions and with dilated pupils for spherical and aspheric IOL on the 100% ETDRS (a) and the 5% ETDRS (b) chart. Circles ( ) are outliers, asterisks ( ) are extreme values. The mean pupil size under visual acuity testing in dim room light was 4.05 mm (SD: 0.85 mm, range from 3.00 to 6.50 mm) in SIOL group and 4.07 (SD: 0.87 mm, range from 3.00 to 6.50 mm) in AIOL group. Under those natural pupil conditions, only spherical aberration (SA) was lower in the aspheric eyes when assessing HOA (Table 2). The mean rhexis diameter was 4.12 mm (SD: 0.53 mm range from 3.50 to 5.75 mm) for the spherical eyes and 4.06 mm (SD: 0.56 mm range from 2.84 to 5.25 mm) for the aspheric Fig. 2. Contrast sensitivity under mesopic lighting conditions (6 cd/m²) for spherical and aspheric IOL (a) and intra-patient difference in contrast sensitivity for both IOLs (b). eyes. Using this analysis diameter, in which the anterior capsule does not influence wave-front analysis, significant differences were found for SA (Table 2). Wave-front errors were largest when measured in mydriasis. Significant differences between the two IOL types were found for SA (Table 2 and Fig. 3), but not when analysing the data for each module, such as for the combined horizontal and vertical trefoil as well as horizontal and vertical coma. Concerning the slitlamp examination, capsular folds were found in only one eye that had received an AIOL. Fig. 3. Differences in all higher order aberrations (HOAs) for natural pupil size (a) and dilated pupils (b). A statistically significant difference was found only in spherical aberration (SA). Circles ( ) are outliers, asterisks ( ) are extreme values. None of the IOLs in either of the groups was visibly decentered. Opticrhexis buttonholing occurred once in each group. Anterior fibrosis, especially of mild extent, occurred in more than 90% of all eyes (spherical group: 19 eyes; AIOL group: 20 eyes), and no significant differences were found between the two IOL groups. Regenerative PCO was either not visible or mild, with a mean severity score (range 0 10, measured with the software) of 0.38 and 0.26 for spherical and aspheric eyes, respectively [p = 0.46]. Discussion The key findings from similar previous trials and the present one comparing e355

4 Table 2. Significant differences that were found in measuring wave-front errors under physiological pupil diameter (PPD), rhexis diameter (RD) and mydriasis (My) aspheric and spherical IOLs are summarized in Table 3. Similar to the majority of published data, this study found no difference in DCVA between spheric (CeeOn Edge, 911A) and aspheric (Tecnis Z9000) IOLs. There was no statistically significant difference in low-contrast DCVA and, surprisingly, no difference in DCVA under mydriasis. A significantly better outcome of contrast sensitivity was found only at a spatial frequency of 12 cycles/degree for the aspheric eyes in mesopic conditions. For all the other spatial frequencies, the aspheric lens showed better contrast sensitivity, but none of the differences was statistically significant. Only in the study by Denoyer et al. comparing the same IOLs, a statistically significant difference between the two lenses was found at all spatial frequencies. Two-thirds of studies SIOL AIOL p-value PPD SA 0.10 lm 0.01 lm < Z(4,0) SD: 0.11 lm SD: 0.02 lm RD SA 0.10 lm 0.01 lm < Z(4,0) SD: 0.07 lm SD: 0.02 lm My SA 0.38 lm 0.10 lm < Z(4,0) SD: 0.11 lm SD: 0.13 lm AIOL, aspheric IOL; SIOL, spherical IOL; and SA, spherical aberration. investigating similar (but not the same) lens design did not report statistical significant difference in contrast sensitivity between the IOLs (Table 3). In assessing the difference in HOA between AIOLs and SIOLs, all studies found statistically significant differences in SA for all pupil diameters, which is consistent with our results. The study by Mu~noz et al. (2006), Denoyer et al. (2007), on the other hand, is the only study reporting a significant difference for total coma for 4- and 6-mm pupil sizes. Studies are also reporting different outcomes for HOA RMS. Three studies found a significant difference for all tested pupil diameters, one only for a large pupil diameter and two, including this study, did not find any statistical difference between the IOLs. Significant differences in SA but only a minor impact on contrast sensitivity are also represented in a post hoc power analysis, which showed that the power of this study was >90% for differences in spherical aberrations between the groups, but only 20% for differences in contrast sensitivity. In a review article about possible benefits of AIOLs by Montes-Mico et al. 2009; most studies calculated the wave-front for a fixed pupil size and not for the individual pupil diameter, as we have carried out in the present study. The influence of pupil size on optical quality of aspheric IOLs was shown by Tabernero et al. 2006, 2009; in only a small percentage of patients. Therefore, the current study confirms those findings suggesting that aspheric IOLs show good results in most patients regardless of pupil size. Standardized measurements for evaluating AIOLs would be necessary to allow a better comparison of results among different trials. Moreover, accurate measurements of tilt and decentration are needed to assess the effect of lens and haptic design on wave-front aberrations. Aspheric IOLs were developed to correct asphericity in eyes with a normal amount of HOAs. So, we would ideally measure HOAs of each patient preoperatively to identify those patients who show very low HOAs and would not benefit from an aspheric IOL, or even be at risk of induction of even worse HOAs. In summary, the improvement in contrast sensitivity in this study was not as pronounced as Table 3. Summary of key findings from similar previous trials and the present study comparing aspheric and spherical IOLs CS HOA BCVA Mesopic Photopic Scotopic Pupil diameter SA Trefoil Total coma Tetrafoil HOA RMS Kasper et al. (2006) NS 3,5 and 6 mm S NS NS NS S (6)* Denoyer et al. (2007) NS S NS 5 mm S Bellucci et al. (2007a) 4 mm S NS S The Moorfields IOL study group (2007) NS NS 4 mm S S Mester et al. (2003) S S S 4 mm S Ohtani et al. (2009) NS NS NS S 4 mm S NS NS Rocha et al. (2006) NS Ph S NS NS NS NS Awwad et al. (2008) NS S** NS 4,5 and 6 mm S NS NS NS S Bellucci et al. (2007b) S S S Mu~noz et al. (2006) NS NS NS 4 and 6 mm S NS S NS Crnej et al. (2011) NS S*** Ph, Rh, My S NS NS NS NS S, significant difference; NS, no significant difference; BCVA, best corrected visual acuity; CS, contrast sensitivity; HOA, higher order aberrations; SA, spherical aberration; RMS, root mean square; Ph, physiological pupil size; Rh, rhexis diameter; and My, mydriasis. * Only for certain pupil sizes. ** At 12 and 18 cycles/degree. *** At 12 cycles/degree. Studies comparing the same IOLs as the current study. e356

5 reported in previous studies; however, a significant improvement could be shown for the spatial frequency of 12 cycles/degree, and the study confirmed the majority of data already published that eyes with implanted aspheric IOLs don t have better visual acuity than spherical IOLs. Acknowledgements Funding and financial disclosures The authors indicate no financial support. None of the authors has any financial disclosures. OF is a member of a scientific advisory board of Abott Medical Optics. He has no financial interest in any of the products mentioned. References Awwad ST, Warmerdam D, Bowman RW, Dwarakanathan S, Cavanagh HD & McCulley JP (2008): Contrast sensitivity and higher order aberrations in eyes implanted with Acrysof IQ SN60WF and Acrysof SN60AT intraocular lenses. J Refract Surg 24: Bellucci R, Morselli S & Pucci V (2007a): Spherical aberration and coma with an aspheric and a spherical intra-ocular lens in normal age-matched eyes. J Cataract Refract Surg 33: Bellucci R, Scialdone A, Buratto L, Morselli S, Chierego C, Criscuoli A, Moretti G & Piers P (2007b): Visual acuity and contrast sensitivity comparison between Tecnis and Acry- Sof SA60AT intraocular lens: A multicenter randomized study. J Cataract Refract Surg 31: Brunette I, Bueno JM, Parent M, Hamam H & Simonet P (2003): Monochromatic aberrations as a function of age, from childhood to advanced age. Invest Ophthalmol Vis Sci 44: Crnej A, Hirnschall N, Nishi Y, Gangwani V, Tabernero J, Artal P & Findl O (2011): Impact of intraocular lens haptic design and orientation on decentration and tilt. J Cataract Refract Surg 37: Denoyer A, Le Lez ML, Majzoub S & Pisella PJ (2007): Quality of vision after cataract surgery after Tecnis Z9000 intraocular lens implantation; Effect of contrast sensitivity and wave-front aberration improvements on the quality of daily vision. J Cataract Refract Surg 33: Findl O, Buehl W, Menapace R, Georgopoulos M, Rainer G, Siegl H, Kaider A & Prinz A (2003): Comparison of 4 methods for quantifying posterior capsule opacification. J Cataract Refract Surg 29: Glasser A & Campbell MC (1998): Presbyopia and the optical changes in the human crystalline lens with age. Vision Res 38: Guirao A, Redondo M, Geraghty E, Piers P, Norrby S & Artal P (2002): Corneal optical aberrations and retinal image quality in patients in whom monofocal intraocular lenses were implanted. Arch Ophthalmol 120: He JC, Gwiazda J, Thorn F & Held R (2003): Wave-front aberrations in the anterior corneal surface and the whole eye. J Opt Soc Am A Opt Image Sci Vis 20: Kasper T, B uhren J & Kohnen T (2006): Intraindividual comparison of higher-order aberrations after implantation of aspheric and spherical intraocular lenses as a function of pupil diameter. J Cataract Refract Surg 32: Mester U, Dillinger P & Anterist N (2003): Impact of a modified optic design on visual function: Clinical comparative study. J Cataract Refract Surg 29: Montes-Mico R, Ferrer-Blasco T & Cervi~no A (2009): Analysis of the possible benefits of aspheric intraocular llenses: review of the literature. J Cataract Refract Surg 35: Mu~noz G, Albarran-Diego C, Montes-Mico R, Rodriguez-Galietero A & Alio JL (2006): Spherical aberration and contrast sensitivity after cataract surgery with the Tecnis Z9000 intraocular lens. J Cataract Refract Surg 32: Ohtani S, Gekka S, Honbou M, Kataoka Y, Minami K, Miyata K & Oshika T (2009): One-year prospective intra-patient comparison of aspherical and spherical intraocular lenses in patients with bilateral cataract. Am J Ophthalmol 147: Packer M, Fine IH & Hoffman RS (2004): Wave-front technology in cataract surgery. Curr Opin Ophthalmol 15: Rocha KM, Soriano ES, Chalita MR, Yamada AC, Bottos K, Bottos J, Morimoto L & Nose W (2006): Wave-front analysis and contrast sensitivity of aspheric and spherical intraocular lenses: a randomized prospective study. Am J Ophthalmol 142: Smith G, Cox MJ, Calver R & Garner LF (2001): The spherical aberration of the crystalline lens of the human eye. Vision Res 41: Tabernero J, Piers P, Benito A, Redondo M & Artal P (2006): Predicting the optical performance of eyes implanted with IOLs to correct spherical aberration. Invest Ophthalmol Vis Sci 47: Tabernero J, Atchoson DA & Makrwell EL (2009): Aberrations and Pupil location under corneal topography and Hartmann- Shack illumination conditions. Invest Ophthalmol Vis Sci 50: The Moorfields IOL study group (2007): Binocular implantation of the Tecnis Z9000 or Acrysof MA60AC intraocular lens in routine cataract surgery. Prospective randomized controlled trial comparing VF-14 scores. J Cataract Refract Surg 33: Received on April 24th, Accepted on December 10th, Correspondence: Oliver Findl, MD, MBA Department of Ophthalmology VIROS Vienna Institute for Research in Ocular Surgery (VIROS), a Karl Landsteiner Institute Heinrich-Collin-Straße Vienna Austria Tel: Fax: oliver@findl.at e357

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