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Comparison of reading performance after bilateral implantation of multifocal intraocular lenses with +3.00 or +4.00 diopter addition
ARTICLE
Comparison of reading performance after bilateral implantation of multifocal intraocular lenses with D3.00 or D4.00 diopter addition Marcony R. Santhiago, MD, Marcelo V. Netto, MD, PhD, Rodrigo F. Espindola, MD, Maysa G. Mazurek, MD, Beatriz de A.F. Gomes, MD, Tais R.R. Parede, MD, Hooman Harooni, MD, Newton Kara-Junior, MD, PhD
PURPOSE: To compare reading ability after cataract surgery and bilateral implantation of multifocal intraocular lenses (IOLs) with a C3.00 diopter (D) addition (add) or a C4.00 D add. SETTING: Department of Ophthalmology, University of Sa˜o Paulo, Sa˜o Paulo, Brazil. DESIGN: Prospective comparative study. METHODS: Patients scheduled for cataract surgery were randomly assigned to bilateral implantation of an aspheric AcrySof ReSTOR multifocal IOL with a C3.00 diopter (D) addition (add) or a C4.00 D add. The reading speed, critical print size, and reading acuity were measured binocularly with best correction using MNREAD acuity charts 6 months after surgery. Patients were tested with the chart at the best patient-preferred reading distance and at 40 cm. Binocular uncorrected and best distancecorrected visual acuities at far and near were also measured. RESULTS: The study enrolled 32 patients. At the best reading distance, the results were similar between the 2 IOL groups in all reading parameters. When tested at 40 cm, reading speed at all print sizes from 0.3 to 0.0 (all P<.001), critical print size (P<.001), and reading acuity (P Z .014) were statistically significantly better in the C3.00 D IOL group than in the C4.00 D IOL group. Uncorrected and corrected visual acuities at far and near were similar between the 2 groups. CONCLUSION: Although the 2 IOL groups had similar performance in reading parameters, patients had to adjust to their best reading distance. The C3.00 D IOL performed better than the C4.00 D IOL at 40 cm. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2010; 36:1874–1879 Q 2010 ASCRS and ESCRS
The loss of reading ability can significantly affect a patient’s quality of life.1–4 New multifocal intraocular lenses (IOLs) with different designs and optical properties were designed to reestablish good functional visual acuity after cataract surgery. Reading ability as a measure of functional vision is a useful way to determine whether multifocal IOLs are meeting the needs of patients and whether patients’ ability to perform daily activities improves as a result.5–9 The aim of this prospective comparative study was to determine whether bilateral implantation of an aspheric multifocal IOL with a C3.00 diopter (D) addition (add) provides better performance in reading speed, reading acuity, and critical print size than the same model aspheric multifocal IOL with a C4.00 D add. 1874
Q 2010 ASCRS and ESCRS Published by Elsevier Inc.
PATIENTS AND METHODS This prospective randomized double-masked comparative clinical study included consecutive patients referred to the Department of Ophthalmology, University of São Paulo, for cataract surgery and bilateral IOL implantation. An institutional review board approved the study, which adhered to the tenets of the Declaration of Helsinki. All patients provided informed consent. Enrolled patients were older than 40 years, had bilateral visually significant cataract, and had corneal astigmatism less than 1.00 D. Exclusion criteria were previous intraocular surgery, ocular disease (eg, corneal opacity or irregularity, dry eye), amblyopia, anisometropia, glaucoma, retinal abnormalities, surgical complications, IOL tilt, IOL decentration greater than 0.4 mm (estimated by retroillumination), and incomplete follow-up. 0886-3350/$dsee front matter doi:10.1016/j.jcrs.2010.05.022
READING METRICS WITH A +3.00 D ADD MULTIFOCAL IOL
Intraocular Lenses Patients were randomized for bilateral implantation of AcrySof ReSTOR SN6AD1 IOLs with a C3.00 D add or AcrySof ReSTOR SN6AD3 IOLs with a C4.00 D add (both Alcon, Inc.). According to the manufacturer, the apodized diffractive multifocal IOLs were designed to achieve satisfactory functional vision at far, intermediate, and near without compromising visual performance. The optical surface of the IOLs is refractive at the periphery for distance vision and apodized diffractive at the central 3.6 mm of the anterior surface for distance and near vision. The diffractive steps are greater in the center of the IOL to give a greater proportion of light to near vision.10–17 The C3.00 D add IOL was designed as an alternative to the C4.00 D add model to provide better intermediate vision or extended reading distance.18–21 Immersion ultrasound biometry (Ocuscan RxP, Alcon, Inc.) was performed in all cases by a single experienced examiner. All eyes were targeted for emmetropia.
Surgical Technique An experienced surgeon (M.R.S.) performed all surgeries. The technique included standardized small-incision phacoemulsification and IOL implantation in the capsular bag.
Patient Evaluation Patients were examined preoperatively and postoperatively at 1, 7, and 30 days and at 3 and 6 months. A physician who was unaware of the study’s objective assessed visual acuity postoperatively. Binocular uncorrected (UDVA) and corrected (CDVA) distance visual acuities were measured at 100% contrast using Early Treatment of Diabetic Retinopathy Study (ETDRS) charts (Precision Vision) under photopic conditions (target luminance 85 candelas [cd]/m2) at 4.0 m. Binocular uncorrected near visual acuity (UNVA) and distance-corrected near visual acuity (DCNVA) were measured using the Logarithmic Visual Acuity Chart 2000 New ETDRS (Precision Vision) at 40.0 cm under photopic conditions (85 cd/m2). To test the best patient-preferred reading distance, the patient held the new ETDRS chart at the optimum distance for reading the smallest line; that distance was measured with a ruler and recorded. Light conditions were controlled with a light meter (Gossen-Starlite). Pupil diameter was measured with a Colvard pupillometer (Oasis Medical) under photopic conditions (85.0 cd/m2), mesopic conditions (3.0 cd/m2), and scotopic (1.5 cd/m2) conditions. Reading parameters (maximum reading speed, reading acuity, critical print size) were assessed using MNREAD
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acuity charts. These continuous-text charts measure the reading acuity and reading speed of normal-vision and low-vision patients. The infinity-corrected manifest refraction (referred to as the adjusted manifest refraction) in each eye was obtained by subtracting 0.25 D from the distance manifest refraction to account for the 4 m testing distance. The adjusted manifest refraction was placed in front of both eyes for MNREAD testing and to evaluate the best reading distance preferred by the patient.A The MNREAD charts use the following definitions: (1) The mean reading speed of the fixed value (ie, level at which no further increase in reading speed occurs) is the maximum reading speed. (2) The smallest character with which maximum reading speed is attained is the critical print size. (3) The smallest character the patient can read, regardless of speed, is the reading acuity. The values obtained can be adjusted for nonstandard viewing distances. One investigator held a blank piece of card to cover the sentences below the one being read. The investigator and the patient were masked to which multifocal IOLs the patient had. Light conditions were controlled with the same light meter used for visual acuity testing. The reading chart consists of individual sentences of 10 to 14 words each. Each sentence contains 60 characters (including a space between words and at the end of each line) printed as 3 lines with even left and right margins. The character contrast is approximately 85%. The vocabulary used in the chart was selected from words appearing with high frequency early in elementary school. The MNREAD reading acuity chart contains sentences written in 19 print sizes. At a distance of 40 cm (16 inches), the print size ranges from 1.3 to 0.5 logMAR. Each sentence is 0.1 logMAR units smaller than the previous sentence. Binocular reading ability was measured under bright light conditions (85.0 cd/m2) using the vertical version of the MNREAD chart at the best patient-preferred reading distance. The distance was measured with a ruler. This condition provides patients with their best near acuity at a distance they preferred. Appropriate calculations were performed to standardize results between patients (ie, the corrected logMAR was used for varying distances). On a separate visit, the same test was given at 40 cm. For reading speed, the patient read the words on the chart aloud beginning with the largest characters and continued to read the sentence at each character size. The time required for reading was recorded. A stopwatch was used to measure the time (seconds) taken to read a given sentence. Reading speed in words per minute (wpm) for each sentence was calculated as follows: 600/reading time (seconds).
Statistical Analysis Submitted: March 5, 2010. Final revision submitted: May 18, 2010. Accepted: May 19, 2010. From Cole Eye Institute (Santhiago, Harooni), Cleveland Clinic Foundation, Cleveland, Ohio, USA; Ophthalmology Departments, University of Sa˜o Paulo (Santhiago, Netto, Espindola, Mazurek, Kara-Junior, Parede), Sa˜o Paulo, and Federal University of Rio de Janeiro (Gomes), Rio de Janeiro, Brazil. Corresponding author: Marcony R. Santhiago, MD, Cole Eye Institute, Cleveland Clinic, 1700 East 13th Street, Apt. 15W, Cleveland, Ohio 44114, USA. E-mail: [email protected].
Statistical analysis was performed using SPSS for Windows software (version 11.5, SPSS, Inc.). LogMAR notation was used for statistical analysis of visual acuity and logRAD notation for reading parameters; logRAD is the reading acuity equivalent of logMAR visual acuity. Normality was checked using the Kolmogorov-Smirnov test; the data did not fulfill the criteria for normal distribution. The analysis was therefore based on a non-normal data distribution. The nonparametric MannWhitney U test was used to compare data between the 2 IOL groups. The statistical tests were conducted at an a level of 0.05. The Fisher exact test was used to detect differences between the 2 IOL groups in patient sex and the Student t test to detect differences in patient age.
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RESULTS The study enrolled 32 patients; 15 (46.0%) were men and 17 (54.0%) were women. Both the C3.00 D IOL group and C4.00 D IOL group comprised 16 patients (32 eyes). The mean age of the 7 men (43.8%) and 9 women (56.2%) in the C3.00 D IOL group was 57.9 years G 7.2 (SD). The mean age of the 8 men (50.0%) and 8 women (50.0%) in the C4.00 D IOL group was 56.2 G 7.8 years. There was no statistically significant difference between the 2 groups in sex (P Z .1, Fisher exact test) or age (P Z .483, Student t test). No patient was lost to follow-up. Preoperatively, there was no statistically significant difference between the 2 groups in mean IOL power calculation (P Z .797), mean axial length (P Z .431), mean CDVA (0.448), mean DCNVA (P Z .768), mean spherical equivalent (P Z .532), mean astigmatism diopters (P Z .752), or mean corneal curvature (P Z .545). Table 1 shows the mean 6-month postoperative values for SE, visual acuity, pupil sizes under different lighting conditions, and best reading distance by group as well as the P values for the comparisons between the 2 groups. The only statistically significant difference between the 2 groups was the best patient-preferred reading distance, which was greater in the C3.00 D IOL group than in the C4.00 D IOL group (P Z .007). At the best patient-preferred reading distance, there was no statistically significant difference in the mean reading speed between the 2 IOL groups at any print size (PO.05, Mann-Whitney U test) (Figure 1). At 6 months, the mean maximum reading speed at 40 cm was 369.7 G 32.3 wpm in the C3.00 D IOL group and 368.0 G 33.3 wpm in the C4.00 D IOL group; the difference was not statistically significant (P Z .715,
Mann-Whitney U test). However, there was a significant difference in mean reading speed in favor of the C3.00 D IOL group at all print sizes from 0.3 to 0.0 logRAD (all P!.001, Mann-Whitney U test) (Figure 2). Table 2 shows the mean values for critical print size and reading acuity. There were statistically significant differences between the 2 IOL groups in critical print size at 40 cm and reading acuity at 40 cm (P!.001 and P Z .014, respectively; Mann-Whitney U test) at 40 cm (Table 2). Both values were better in the C3.00 D IOL group than in the C4.00 D IOL group. There were no intraoperative complications. Six months postoperatively, all IOLs were well centered. There were no cases of posterior capsule opacification, clinically significant cystoid macular edema, prolonged intraocular pressure increase, or prolonged corneal edema. DISCUSSION Although the visual performance with multifocal IOLs of different designs has been evaluated, there are few studies of the reading ability of patients with bilateral multifocal IOLs. In this study, we compared reading speed, critical print size, and reading acuity of patients with bilateral AcrySof ReSTOR SN6AD1 multifocal IOLs with a C3.00 D add and patients with bilateral AcrySof ReSTOR SN6AD3 multifocal IOLs with a C4.00 D add. These parameters were tested at the best patient-preferred reading distance and at 40 cm. The main finding in our study was that the reading performance at best patient-preferred reading distance was similar between patients in the C3.00 D IOL group and patients in the C4.00 D IOL group. Theoretically, the 2 IOLs differ in the distance to optimum near visual acuity because they have different add powers.
Table 1. Postoperative data. Mean G SD Parameter SE (D) UNVA (logMAR) DCNVA (logMAR) UDVA (logMAR) CDVA (logMAR) Scotopic pupil (mm) Mesopic pupil (mm) Photopic pupil (mm) Best reading distance (cm)
C3.00 D IOL 0.29 G 0.27 0.022 G 0.08 0.003 G 0.08 0.032 G 0.07 0.006 G 0.07 4.72 G 0.68 4.02 G 0.41 3.49 G 0.52 39.7 G 1.45
C4.00 D IOL P Value 0.21 G 0.32 0.028 G 0.08 0.022 G 0.07 0.023 G 0.07 0.003 G 0.06 4.69 G 0.61 4.00 G 0.42 3.47 G 0.48 31.6 G 1.01
.832 .717 .359 .638 .548 .790 .947 .756 .007*
CDVA Z corrected distance visual acuity; DCNVA Z distance-corrected near visual acuity; IOL Z intraocular lens; SE Z spherical equivalent; UNVA Z uncorrected near visual acuity; UDVA Z uncorrected distance visual acuity *Statistically significant
Figure 1. Mean reading speed (on logarithmic scale) at the best patient-preferred reading distance (distance from chart) (IOL Z intraocular lens; wpm Z words per minute).
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Table 2. Critical print size and reading acuity. Mean (LogMAR) G SD Parameter
C3.00 D IOL C4.00 D IOL P Value
Critical print size at 40 cm Reading acuity at 40 cm Critical print size at BRD Reading acuity at BRD
0.38 G 0.08 0.56 G 0.07 !.001* 0.019 G 0.07 0.075 G 0.07 .014* 0.38 G 0.11 0.37 G 0.08 .333 0.019 G 0.09 0.025 G 0.10 .718
BRD Z best patient-preferred reading distance; IOL Z intraocular lens *Statistically significant
Figure 2. Mean reading speed (on logarithmic scale) at 40 cm (distance from chart) (IOL Z intraocular lens; wpm Z words per minute).
Based on our results, we conclude that patients with bilateral implantation of the C3.00 D IOL are able to read at a more comfortable distance; however, the distance at which the patient is used to reading or working with near tasks should be evaluated preoperatively. Our results confirm findings in previous studies of the peak near vision in patients with the C3.00 D IOL we used in our study. Kohnen et al.20 evaluated visual function after bilateral implantation of the C3.00 D IOL. They found the mean patient-preferred near distance was 41 G 4 cm; the defocus curve showed a plateau of optimum near vision that was 0.04 logMAR from the vergence of 2.0 to 2.5 D, the equivalent of 40 to 50 cm from the eye. In our study, tests performed at 40 cm showed a significant difference in favor of the C3.00 D IOL group. The C3.00 D IOL group had better reading speed at print sizes of 0.4, 0.3, 0.2, 0.1, and 0.0 logMAR and better critical print size and reading acuity results. These findings were expected because of the lower add of the C3.00 D IOL. There was no statistically significant difference between the groups in the maximum reading speed at print sizes higher than 0.4 logMAR. Others studies using the MNREAD chart5,22 report that reading speed was faster with the larger characters and that reading speed did not increase after a certain print size. As previous studies17,23 suggest, caution should be used when interpreting near-vision results in patients with multifocal IOLs with different add powers. Because the theoretical near point for patients with a C4.00 D add IOL is closer than 40 cm, we believe adjusting the reading distance based on patient preference allows for better evaluation of the reading parameters tested in this subgroup of patients. We evaluated UNVA and DCNVA at 40 cm and expected that patients with bilateral C3.00 D IOLs
would have better performance than patients with bilateral C4.00 D IOLs. Although there was a trend toward better near visual acuity tested with the ETDRS near chart at 40 cm in the C3.00 D IOL group, the results were not statistically significantly different than those in the C4.00 D IOL group. A study with a larger sample size would likely produce significant results, as shown in a previous study.19 Our results show that the visual function evaluation after cataract surgery with multifocal IOL implantation should include an assessment of reading ability. In our study, there was a significant difference between the 2 IOL groups on the MNREAD reading test at 40 cm; however, there were no significant differences with the ETDRS near acuity charts at 40 cm. Gupta et al.6 recommend that near visual ability measurement in presbyopic eyes be standardized to include assessment of near visual acuity with logMAR uppercase-letter optotypes, critical print size, and reading speed. Assessing reading speed with different logMAR or logRAD print sizes is particularly relevant because it simulates everyday life situations, such as reading newspapers, books, and magazines. A reading speed of 80 wpm is the lower limit for recreational sensecapturing reading.24,25 In our study, the mean reading speed was faster than 80 wpm at all print sizes in both IOL groups, even when there were significant differences between the 2 groups. In addition, most magazines and journals have a characters lager than 0.4 logRAD. At print sizes larger than that, the 2 IOL groups performed similarly, even when tested at 40 cm. Measuring reading ability is always challenging. Experts in the field believe that the best definition of reading is the ability to derive meaning from text.26,27 We believe reading speed in this regard would be better analyzed in patients with a multifocal IOL in 1 eye and another type of multifocal IOL in the fellow eye, in which case the patient would serve as his or her own control. However, a study design in which patients have the same multifocal IOL in both eyes allows bilateral analyses and is more representative
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of real life. In attempting to reduce intellectual biases, we studied the reading metrics of the MNREAD acuity chart. The test sentences provide samples of simple vocabulary and normal reading material that demand corresponding visual-processing capabilities and eyemovement control. The maximum reading speed in our study would be considered fast. A mean speed of 350 wpm or more is much faster than speed at which people usually read a book (160 to 200 wpm).26 We believe the speed was higher in our study because the maximum reading speed was obtained in a setting in which the patients were motivated to read as quickly and accurately as possible. In addition, the vocabulary used in MNREAD chart sentences are selected from words that appear with high frequency in the early school years and reading speed is strongly dependent on other cortical and nonvisual processes, such as memory and comprehension. We believe these factors significantly contributed to increase over the usual speed of, for example, reading a book. A concern with respect to the MNREAD chart is that each sentence has 60 characters and it is assumed that this is consistent with 10 standard-length words of 6 letters. However, in many languages, books and newspapers usually contain words with more than 5 or 6 letters. Keeping these concerns in mind, we believe the results obtained with MNREAD charts were sufficient considering the comparative design of our study. As previous studies show,5,22 assessment of reading speed with the MNREAD chart is a useful measure of near visual function in cases of presbyopia because it gives an indication of reading fluency. A limitation of our study is that we tested patients under 1 lighting condition (bright light). However, that is the standard illumination for the MNREAD test. Pupils were carefully measured under light and dark conditions, but only with distance gaze. The natural pupil constriction that occurs with near focus cannot be neglected. The near pupil sizes in light and dark cannot be assumed to be the same as for distance. The light-energy distribution with some IOLs, such as the multifocal IOLs in our study, is based on changes in pupil size. Checking for a similarity in distance pupil size between groups may have missed between-group differences at near. Although different light conditions might be more representative of daily activities, we believe the reading speed test under dim light would produce similar results because the multifocal IOLs involved in our study have similar surfaces; that is, both are apodized diffractive, and the apodization is in the central 3.6 mm. Another limitation of our study was the sample size. A larger sample would allow more meaningful statistical comparisons and perhaps yield more significant results.
In conclusion, patients with bilateral AcrySof ReSTOR SN6AD1 multifocal IOLs with a C3.00 D add and patients with bilateral AcrySof ReSTOR SN6AD3 multifocal IOLs with a C4.00 D add had a similar performance in reading metrics; however, they had to adjust for best reading vision. Although the near DCNVA and UNVA results were similar between the 2 groups, there were differences in reading ability. At 40 cm, patients in the C3.00 D IOL group performed better than patients in the C4.00 D IOL group in reading metrics. Preoperative evaluation of these patients should determine at what distances patients read and work; such assessment would likely provide better postoperative reading metric results. REFERENCES 1. Uusitalo RJ, Brans T, Pessi T, Tarkkanen A. Evaluating cataract surgery gains by assessing patients’ quality of life using the VF-7. J Cataract Refract Surg 1999; 25:989–994 2. Richter-Mueksch S, Weghaupt H, Skorpik C, Velikay-Parel M, Radner W. Reading performance with a refractive multifocal and a diffractive bifocal intraocular lens. J Cataract Refract Surg 2002; 28:1957–1963 3. Stifter E, Sacu S, Weghaupt H, Ko¨nig F, Richter-Mu¨ksch S, Thaler A, Velikay-Parel M, Radner W. Reading performance depending on the type of cataract and its predictability on the visual outcome. J Cataract Refract Surg 2004; 30:1259–1267 4. Mo¨nestam E, Wachtmeister L. The impact of cataract surgery on low vision patients; a population based study. Acta Ophthalmol Scand 1997; 75:569–576. Available at: http://www3.interscience. wiley.com/cgi-bin/fulltext/122407197/PDFSTART. Accessed July 13, 2010 5. Brown D, Dougherty P, Gills JP, Hunkeler J, Sanders DR, Sanders ML. Functional reading acuity and performance: comparison of 2 accommodating intraocular lenses. J Cataract Refract Surg 2009; 35:1711–1714 6. Gupta N, Wolffsohn JSW, Naroo SA. Comparison of near visual acuity and reading metrics in presbyopia correction. J Cataract Refract Surg 2009; 35:1401–1409 7. Hu¨tz WW, Eckhardt HB, Ro¨hrig B, Grolmus R. Reading ability with 3 multifocal intraocular lens models. J Cataract Refract Surg 2006; 32:2015–2021 8. Harman FE, Maling S, Kampougeris G, Langan L, Khan I, Lee N, Bloom PA. Comparing the 1CU accommodative, multifocal, and monofocal intraocular lenses; a randomized trial. Ophthalmology 2008; 115:993–1001. Available at: http://download.journals. elsevierhealth.com/pdfs/journals/0161-6420/PIIS0161642007009608. pdf. Accessed July 13, 2010 9. Hu¨tz WW, Eckhardt HB, Ro¨hrig B, Grolmus R. Intermediate vision and reading speed with Array, Tecnis, and ReSTOR intraocular lenses. J Refract Surg 2008; 24:251–256 10. Chang DF. Prospective functional and clinical comparison of bilateral ReZoom and ReSTOR intraocular lenses in patients 70 years or younger. J Cataract Refract Surg 2008; 34:934–941 11. Kohnen T, Allen D, Boureau C, Dublineau P, Hartmann C, Mehdorn E, Rozot P, Tassinari G. European multicenter study of the AcrySof ReSTOR apodized diffractive intraocular lens. Ophthalmology 2006; 113:578–584. Available at: http://download.journals. elsevierhealth.com/pdfs/journals/0161-6420/PIIS0161642005014405. pdf. Accessed July 13, 2010 12. Ferrer-Blasco T, Monte´s-Mico´ R, Cervin˜o A, Alfonso JF, Gonza´lez-Me´ijome JM. Stereoacuity after refractive lens exchange
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First author: Marcony R. Santhiago, MD Ophthalmology Departments, University of São Paulo, São Paulo, Brazil and Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
Comparison of reading performance after bilateral implantation of multifocal intraocular lenses with D3.00 or D4.00 diopter addition Marcony R. Santhiago, MD, Marcelo V. Netto, MD, PhD, Rodrigo F. Espindola, MD, Maysa G. Mazurek, MD, Beatriz de A.F. Gomes, MD, Tais R.R. Parede, MD, Hooman Harooni, MD, Newton Kara-Junior, MD, PhD
PURPOSE: To compare reading ability after cataract surgery and bilateral implantation of multifocal intraocular lenses (IOLs) with a C3.00 diopter (D) addition (add) or a C4.00 D add. SETTING: Department of Ophthalmology, University of Sa˜o Paulo, Sa˜o Paulo, Brazil. DESIGN: Prospective comparative study. METHODS: Patients scheduled for cataract surgery were randomly assigned to bilateral implantation of an aspheric AcrySof ReSTOR multifocal IOL with a C3.00 diopter (D) addition (add) or a C4.00 D add. The reading speed, critical print size, and reading acuity were measured binocularly with best correction using MNREAD acuity charts 6 months after surgery. Patients were tested with the chart at the best patient-preferred reading distance and at 40 cm. Binocular uncorrected and best distancecorrected visual acuities at far and near were also measured. RESULTS: The study enrolled 32 patients. At the best reading distance, the results were similar between the 2 IOL groups in all reading parameters. When tested at 40 cm, reading speed at all print sizes from 0.3 to 0.0 (all P<.001), critical print size (P<.001), and reading acuity (P Z .014) were statistically significantly better in the C3.00 D IOL group than in the C4.00 D IOL group. Uncorrected and corrected visual acuities at far and near were similar between the 2 groups. CONCLUSION: Although the 2 IOL groups had similar performance in reading parameters, patients had to adjust to their best reading distance. The C3.00 D IOL performed better than the C4.00 D IOL at 40 cm. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2010; 36:1874–1879 Q 2010 ASCRS and ESCRS
The loss of reading ability can significantly affect a patient’s quality of life.1–4 New multifocal intraocular lenses (IOLs) with different designs and optical properties were designed to reestablish good functional visual acuity after cataract surgery. Reading ability as a measure of functional vision is a useful way to determine whether multifocal IOLs are meeting the needs of patients and whether patients’ ability to perform daily activities improves as a result.5–9 The aim of this prospective comparative study was to determine whether bilateral implantation of an aspheric multifocal IOL with a C3.00 diopter (D) addition (add) provides better performance in reading speed, reading acuity, and critical print size than the same model aspheric multifocal IOL with a C4.00 D add. 1874
Q 2010 ASCRS and ESCRS Published by Elsevier Inc.
PATIENTS AND METHODS This prospective randomized double-masked comparative clinical study included consecutive patients referred to the Department of Ophthalmology, University of São Paulo, for cataract surgery and bilateral IOL implantation. An institutional review board approved the study, which adhered to the tenets of the Declaration of Helsinki. All patients provided informed consent. Enrolled patients were older than 40 years, had bilateral visually significant cataract, and had corneal astigmatism less than 1.00 D. Exclusion criteria were previous intraocular surgery, ocular disease (eg, corneal opacity or irregularity, dry eye), amblyopia, anisometropia, glaucoma, retinal abnormalities, surgical complications, IOL tilt, IOL decentration greater than 0.4 mm (estimated by retroillumination), and incomplete follow-up. 0886-3350/$dsee front matter doi:10.1016/j.jcrs.2010.05.022
READING METRICS WITH A +3.00 D ADD MULTIFOCAL IOL
Intraocular Lenses Patients were randomized for bilateral implantation of AcrySof ReSTOR SN6AD1 IOLs with a C3.00 D add or AcrySof ReSTOR SN6AD3 IOLs with a C4.00 D add (both Alcon, Inc.). According to the manufacturer, the apodized diffractive multifocal IOLs were designed to achieve satisfactory functional vision at far, intermediate, and near without compromising visual performance. The optical surface of the IOLs is refractive at the periphery for distance vision and apodized diffractive at the central 3.6 mm of the anterior surface for distance and near vision. The diffractive steps are greater in the center of the IOL to give a greater proportion of light to near vision.10–17 The C3.00 D add IOL was designed as an alternative to the C4.00 D add model to provide better intermediate vision or extended reading distance.18–21 Immersion ultrasound biometry (Ocuscan RxP, Alcon, Inc.) was performed in all cases by a single experienced examiner. All eyes were targeted for emmetropia.
Surgical Technique An experienced surgeon (M.R.S.) performed all surgeries. The technique included standardized small-incision phacoemulsification and IOL implantation in the capsular bag.
Patient Evaluation Patients were examined preoperatively and postoperatively at 1, 7, and 30 days and at 3 and 6 months. A physician who was unaware of the study’s objective assessed visual acuity postoperatively. Binocular uncorrected (UDVA) and corrected (CDVA) distance visual acuities were measured at 100% contrast using Early Treatment of Diabetic Retinopathy Study (ETDRS) charts (Precision Vision) under photopic conditions (target luminance 85 candelas [cd]/m2) at 4.0 m. Binocular uncorrected near visual acuity (UNVA) and distance-corrected near visual acuity (DCNVA) were measured using the Logarithmic Visual Acuity Chart 2000 New ETDRS (Precision Vision) at 40.0 cm under photopic conditions (85 cd/m2). To test the best patient-preferred reading distance, the patient held the new ETDRS chart at the optimum distance for reading the smallest line; that distance was measured with a ruler and recorded. Light conditions were controlled with a light meter (Gossen-Starlite). Pupil diameter was measured with a Colvard pupillometer (Oasis Medical) under photopic conditions (85.0 cd/m2), mesopic conditions (3.0 cd/m2), and scotopic (1.5 cd/m2) conditions. Reading parameters (maximum reading speed, reading acuity, critical print size) were assessed using MNREAD
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acuity charts. These continuous-text charts measure the reading acuity and reading speed of normal-vision and low-vision patients. The infinity-corrected manifest refraction (referred to as the adjusted manifest refraction) in each eye was obtained by subtracting 0.25 D from the distance manifest refraction to account for the 4 m testing distance. The adjusted manifest refraction was placed in front of both eyes for MNREAD testing and to evaluate the best reading distance preferred by the patient.A The MNREAD charts use the following definitions: (1) The mean reading speed of the fixed value (ie, level at which no further increase in reading speed occurs) is the maximum reading speed. (2) The smallest character with which maximum reading speed is attained is the critical print size. (3) The smallest character the patient can read, regardless of speed, is the reading acuity. The values obtained can be adjusted for nonstandard viewing distances. One investigator held a blank piece of card to cover the sentences below the one being read. The investigator and the patient were masked to which multifocal IOLs the patient had. Light conditions were controlled with the same light meter used for visual acuity testing. The reading chart consists of individual sentences of 10 to 14 words each. Each sentence contains 60 characters (including a space between words and at the end of each line) printed as 3 lines with even left and right margins. The character contrast is approximately 85%. The vocabulary used in the chart was selected from words appearing with high frequency early in elementary school. The MNREAD reading acuity chart contains sentences written in 19 print sizes. At a distance of 40 cm (16 inches), the print size ranges from 1.3 to 0.5 logMAR. Each sentence is 0.1 logMAR units smaller than the previous sentence. Binocular reading ability was measured under bright light conditions (85.0 cd/m2) using the vertical version of the MNREAD chart at the best patient-preferred reading distance. The distance was measured with a ruler. This condition provides patients with their best near acuity at a distance they preferred. Appropriate calculations were performed to standardize results between patients (ie, the corrected logMAR was used for varying distances). On a separate visit, the same test was given at 40 cm. For reading speed, the patient read the words on the chart aloud beginning with the largest characters and continued to read the sentence at each character size. The time required for reading was recorded. A stopwatch was used to measure the time (seconds) taken to read a given sentence. Reading speed in words per minute (wpm) for each sentence was calculated as follows: 600/reading time (seconds).
Statistical Analysis Submitted: March 5, 2010. Final revision submitted: May 18, 2010. Accepted: May 19, 2010. From Cole Eye Institute (Santhiago, Harooni), Cleveland Clinic Foundation, Cleveland, Ohio, USA; Ophthalmology Departments, University of Sa˜o Paulo (Santhiago, Netto, Espindola, Mazurek, Kara-Junior, Parede), Sa˜o Paulo, and Federal University of Rio de Janeiro (Gomes), Rio de Janeiro, Brazil. Corresponding author: Marcony R. Santhiago, MD, Cole Eye Institute, Cleveland Clinic, 1700 East 13th Street, Apt. 15W, Cleveland, Ohio 44114, USA. E-mail: [email protected].
Statistical analysis was performed using SPSS for Windows software (version 11.5, SPSS, Inc.). LogMAR notation was used for statistical analysis of visual acuity and logRAD notation for reading parameters; logRAD is the reading acuity equivalent of logMAR visual acuity. Normality was checked using the Kolmogorov-Smirnov test; the data did not fulfill the criteria for normal distribution. The analysis was therefore based on a non-normal data distribution. The nonparametric MannWhitney U test was used to compare data between the 2 IOL groups. The statistical tests were conducted at an a level of 0.05. The Fisher exact test was used to detect differences between the 2 IOL groups in patient sex and the Student t test to detect differences in patient age.
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RESULTS The study enrolled 32 patients; 15 (46.0%) were men and 17 (54.0%) were women. Both the C3.00 D IOL group and C4.00 D IOL group comprised 16 patients (32 eyes). The mean age of the 7 men (43.8%) and 9 women (56.2%) in the C3.00 D IOL group was 57.9 years G 7.2 (SD). The mean age of the 8 men (50.0%) and 8 women (50.0%) in the C4.00 D IOL group was 56.2 G 7.8 years. There was no statistically significant difference between the 2 groups in sex (P Z .1, Fisher exact test) or age (P Z .483, Student t test). No patient was lost to follow-up. Preoperatively, there was no statistically significant difference between the 2 groups in mean IOL power calculation (P Z .797), mean axial length (P Z .431), mean CDVA (0.448), mean DCNVA (P Z .768), mean spherical equivalent (P Z .532), mean astigmatism diopters (P Z .752), or mean corneal curvature (P Z .545). Table 1 shows the mean 6-month postoperative values for SE, visual acuity, pupil sizes under different lighting conditions, and best reading distance by group as well as the P values for the comparisons between the 2 groups. The only statistically significant difference between the 2 groups was the best patient-preferred reading distance, which was greater in the C3.00 D IOL group than in the C4.00 D IOL group (P Z .007). At the best patient-preferred reading distance, there was no statistically significant difference in the mean reading speed between the 2 IOL groups at any print size (PO.05, Mann-Whitney U test) (Figure 1). At 6 months, the mean maximum reading speed at 40 cm was 369.7 G 32.3 wpm in the C3.00 D IOL group and 368.0 G 33.3 wpm in the C4.00 D IOL group; the difference was not statistically significant (P Z .715,
Mann-Whitney U test). However, there was a significant difference in mean reading speed in favor of the C3.00 D IOL group at all print sizes from 0.3 to 0.0 logRAD (all P!.001, Mann-Whitney U test) (Figure 2). Table 2 shows the mean values for critical print size and reading acuity. There were statistically significant differences between the 2 IOL groups in critical print size at 40 cm and reading acuity at 40 cm (P!.001 and P Z .014, respectively; Mann-Whitney U test) at 40 cm (Table 2). Both values were better in the C3.00 D IOL group than in the C4.00 D IOL group. There were no intraoperative complications. Six months postoperatively, all IOLs were well centered. There were no cases of posterior capsule opacification, clinically significant cystoid macular edema, prolonged intraocular pressure increase, or prolonged corneal edema. DISCUSSION Although the visual performance with multifocal IOLs of different designs has been evaluated, there are few studies of the reading ability of patients with bilateral multifocal IOLs. In this study, we compared reading speed, critical print size, and reading acuity of patients with bilateral AcrySof ReSTOR SN6AD1 multifocal IOLs with a C3.00 D add and patients with bilateral AcrySof ReSTOR SN6AD3 multifocal IOLs with a C4.00 D add. These parameters were tested at the best patient-preferred reading distance and at 40 cm. The main finding in our study was that the reading performance at best patient-preferred reading distance was similar between patients in the C3.00 D IOL group and patients in the C4.00 D IOL group. Theoretically, the 2 IOLs differ in the distance to optimum near visual acuity because they have different add powers.
Table 1. Postoperative data. Mean G SD Parameter SE (D) UNVA (logMAR) DCNVA (logMAR) UDVA (logMAR) CDVA (logMAR) Scotopic pupil (mm) Mesopic pupil (mm) Photopic pupil (mm) Best reading distance (cm)
C3.00 D IOL 0.29 G 0.27 0.022 G 0.08 0.003 G 0.08 0.032 G 0.07 0.006 G 0.07 4.72 G 0.68 4.02 G 0.41 3.49 G 0.52 39.7 G 1.45
C4.00 D IOL P Value 0.21 G 0.32 0.028 G 0.08 0.022 G 0.07 0.023 G 0.07 0.003 G 0.06 4.69 G 0.61 4.00 G 0.42 3.47 G 0.48 31.6 G 1.01
.832 .717 .359 .638 .548 .790 .947 .756 .007*
CDVA Z corrected distance visual acuity; DCNVA Z distance-corrected near visual acuity; IOL Z intraocular lens; SE Z spherical equivalent; UNVA Z uncorrected near visual acuity; UDVA Z uncorrected distance visual acuity *Statistically significant
Figure 1. Mean reading speed (on logarithmic scale) at the best patient-preferred reading distance (distance from chart) (IOL Z intraocular lens; wpm Z words per minute).
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Table 2. Critical print size and reading acuity. Mean (LogMAR) G SD Parameter
C3.00 D IOL C4.00 D IOL P Value
Critical print size at 40 cm Reading acuity at 40 cm Critical print size at BRD Reading acuity at BRD
0.38 G 0.08 0.56 G 0.07 !.001* 0.019 G 0.07 0.075 G 0.07 .014* 0.38 G 0.11 0.37 G 0.08 .333 0.019 G 0.09 0.025 G 0.10 .718
BRD Z best patient-preferred reading distance; IOL Z intraocular lens *Statistically significant
Figure 2. Mean reading speed (on logarithmic scale) at 40 cm (distance from chart) (IOL Z intraocular lens; wpm Z words per minute).
Based on our results, we conclude that patients with bilateral implantation of the C3.00 D IOL are able to read at a more comfortable distance; however, the distance at which the patient is used to reading or working with near tasks should be evaluated preoperatively. Our results confirm findings in previous studies of the peak near vision in patients with the C3.00 D IOL we used in our study. Kohnen et al.20 evaluated visual function after bilateral implantation of the C3.00 D IOL. They found the mean patient-preferred near distance was 41 G 4 cm; the defocus curve showed a plateau of optimum near vision that was 0.04 logMAR from the vergence of 2.0 to 2.5 D, the equivalent of 40 to 50 cm from the eye. In our study, tests performed at 40 cm showed a significant difference in favor of the C3.00 D IOL group. The C3.00 D IOL group had better reading speed at print sizes of 0.4, 0.3, 0.2, 0.1, and 0.0 logMAR and better critical print size and reading acuity results. These findings were expected because of the lower add of the C3.00 D IOL. There was no statistically significant difference between the groups in the maximum reading speed at print sizes higher than 0.4 logMAR. Others studies using the MNREAD chart5,22 report that reading speed was faster with the larger characters and that reading speed did not increase after a certain print size. As previous studies17,23 suggest, caution should be used when interpreting near-vision results in patients with multifocal IOLs with different add powers. Because the theoretical near point for patients with a C4.00 D add IOL is closer than 40 cm, we believe adjusting the reading distance based on patient preference allows for better evaluation of the reading parameters tested in this subgroup of patients. We evaluated UNVA and DCNVA at 40 cm and expected that patients with bilateral C3.00 D IOLs
would have better performance than patients with bilateral C4.00 D IOLs. Although there was a trend toward better near visual acuity tested with the ETDRS near chart at 40 cm in the C3.00 D IOL group, the results were not statistically significantly different than those in the C4.00 D IOL group. A study with a larger sample size would likely produce significant results, as shown in a previous study.19 Our results show that the visual function evaluation after cataract surgery with multifocal IOL implantation should include an assessment of reading ability. In our study, there was a significant difference between the 2 IOL groups on the MNREAD reading test at 40 cm; however, there were no significant differences with the ETDRS near acuity charts at 40 cm. Gupta et al.6 recommend that near visual ability measurement in presbyopic eyes be standardized to include assessment of near visual acuity with logMAR uppercase-letter optotypes, critical print size, and reading speed. Assessing reading speed with different logMAR or logRAD print sizes is particularly relevant because it simulates everyday life situations, such as reading newspapers, books, and magazines. A reading speed of 80 wpm is the lower limit for recreational sensecapturing reading.24,25 In our study, the mean reading speed was faster than 80 wpm at all print sizes in both IOL groups, even when there were significant differences between the 2 groups. In addition, most magazines and journals have a characters lager than 0.4 logRAD. At print sizes larger than that, the 2 IOL groups performed similarly, even when tested at 40 cm. Measuring reading ability is always challenging. Experts in the field believe that the best definition of reading is the ability to derive meaning from text.26,27 We believe reading speed in this regard would be better analyzed in patients with a multifocal IOL in 1 eye and another type of multifocal IOL in the fellow eye, in which case the patient would serve as his or her own control. However, a study design in which patients have the same multifocal IOL in both eyes allows bilateral analyses and is more representative
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of real life. In attempting to reduce intellectual biases, we studied the reading metrics of the MNREAD acuity chart. The test sentences provide samples of simple vocabulary and normal reading material that demand corresponding visual-processing capabilities and eyemovement control. The maximum reading speed in our study would be considered fast. A mean speed of 350 wpm or more is much faster than speed at which people usually read a book (160 to 200 wpm).26 We believe the speed was higher in our study because the maximum reading speed was obtained in a setting in which the patients were motivated to read as quickly and accurately as possible. In addition, the vocabulary used in MNREAD chart sentences are selected from words that appear with high frequency in the early school years and reading speed is strongly dependent on other cortical and nonvisual processes, such as memory and comprehension. We believe these factors significantly contributed to increase over the usual speed of, for example, reading a book. A concern with respect to the MNREAD chart is that each sentence has 60 characters and it is assumed that this is consistent with 10 standard-length words of 6 letters. However, in many languages, books and newspapers usually contain words with more than 5 or 6 letters. Keeping these concerns in mind, we believe the results obtained with MNREAD charts were sufficient considering the comparative design of our study. As previous studies show,5,22 assessment of reading speed with the MNREAD chart is a useful measure of near visual function in cases of presbyopia because it gives an indication of reading fluency. A limitation of our study is that we tested patients under 1 lighting condition (bright light). However, that is the standard illumination for the MNREAD test. Pupils were carefully measured under light and dark conditions, but only with distance gaze. The natural pupil constriction that occurs with near focus cannot be neglected. The near pupil sizes in light and dark cannot be assumed to be the same as for distance. The light-energy distribution with some IOLs, such as the multifocal IOLs in our study, is based on changes in pupil size. Checking for a similarity in distance pupil size between groups may have missed between-group differences at near. Although different light conditions might be more representative of daily activities, we believe the reading speed test under dim light would produce similar results because the multifocal IOLs involved in our study have similar surfaces; that is, both are apodized diffractive, and the apodization is in the central 3.6 mm. Another limitation of our study was the sample size. A larger sample would allow more meaningful statistical comparisons and perhaps yield more significant results.
In conclusion, patients with bilateral AcrySof ReSTOR SN6AD1 multifocal IOLs with a C3.00 D add and patients with bilateral AcrySof ReSTOR SN6AD3 multifocal IOLs with a C4.00 D add had a similar performance in reading metrics; however, they had to adjust for best reading vision. Although the near DCNVA and UNVA results were similar between the 2 groups, there were differences in reading ability. At 40 cm, patients in the C3.00 D IOL group performed better than patients in the C4.00 D IOL group in reading metrics. Preoperative evaluation of these patients should determine at what distances patients read and work; such assessment would likely provide better postoperative reading metric results. REFERENCES 1. Uusitalo RJ, Brans T, Pessi T, Tarkkanen A. Evaluating cataract surgery gains by assessing patients’ quality of life using the VF-7. J Cataract Refract Surg 1999; 25:989–994 2. Richter-Mueksch S, Weghaupt H, Skorpik C, Velikay-Parel M, Radner W. Reading performance with a refractive multifocal and a diffractive bifocal intraocular lens. J Cataract Refract Surg 2002; 28:1957–1963 3. Stifter E, Sacu S, Weghaupt H, Ko¨nig F, Richter-Mu¨ksch S, Thaler A, Velikay-Parel M, Radner W. Reading performance depending on the type of cataract and its predictability on the visual outcome. J Cataract Refract Surg 2004; 30:1259–1267 4. Mo¨nestam E, Wachtmeister L. The impact of cataract surgery on low vision patients; a population based study. Acta Ophthalmol Scand 1997; 75:569–576. Available at: http://www3.interscience. wiley.com/cgi-bin/fulltext/122407197/PDFSTART. Accessed July 13, 2010 5. Brown D, Dougherty P, Gills JP, Hunkeler J, Sanders DR, Sanders ML. Functional reading acuity and performance: comparison of 2 accommodating intraocular lenses. J Cataract Refract Surg 2009; 35:1711–1714 6. Gupta N, Wolffsohn JSW, Naroo SA. Comparison of near visual acuity and reading metrics in presbyopia correction. J Cataract Refract Surg 2009; 35:1401–1409 7. Hu¨tz WW, Eckhardt HB, Ro¨hrig B, Grolmus R. Reading ability with 3 multifocal intraocular lens models. J Cataract Refract Surg 2006; 32:2015–2021 8. Harman FE, Maling S, Kampougeris G, Langan L, Khan I, Lee N, Bloom PA. Comparing the 1CU accommodative, multifocal, and monofocal intraocular lenses; a randomized trial. Ophthalmology 2008; 115:993–1001. Available at: http://download.journals. elsevierhealth.com/pdfs/journals/0161-6420/PIIS0161642007009608. pdf. Accessed July 13, 2010 9. Hu¨tz WW, Eckhardt HB, Ro¨hrig B, Grolmus R. Intermediate vision and reading speed with Array, Tecnis, and ReSTOR intraocular lenses. J Refract Surg 2008; 24:251–256 10. Chang DF. Prospective functional and clinical comparison of bilateral ReZoom and ReSTOR intraocular lenses in patients 70 years or younger. J Cataract Refract Surg 2008; 34:934–941 11. Kohnen T, Allen D, Boureau C, Dublineau P, Hartmann C, Mehdorn E, Rozot P, Tassinari G. European multicenter study of the AcrySof ReSTOR apodized diffractive intraocular lens. Ophthalmology 2006; 113:578–584. Available at: http://download.journals. elsevierhealth.com/pdfs/journals/0161-6420/PIIS0161642005014405. pdf. Accessed July 13, 2010 12. Ferrer-Blasco T, Monte´s-Mico´ R, Cervin˜o A, Alfonso JF, Gonza´lez-Me´ijome JM. Stereoacuity after refractive lens exchange
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First author: Marcony R. Santhiago, MD Ophthalmology Departments, University of São Paulo, São Paulo, Brazil and Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA