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Near and intermediate reading performance of a diffractive trifocal intraocular lens using a reading desk
ARTICLE
Near and intermediate reading performance of a diffractive trifocal intraocular lens using a reading desk Mary S.A. Attia, MD, Gerd U. Auffarth, MD, PhD, Ramin Khoramnia, MD, Katharina Linz, MD, Florian T.A. Kretz, MD
PURPOSE: To evaluate reading performance of a trifocal intra-ocular lens (IOL) at near and intermediate distances using the Salzburg Reading Desk. SETTING: International Vision Correction Research Centre and David J. Apple Laboratory, University Eye Clinic, Heidelberg, Germany. DESIGN: Prospective, nonrandomized clinical study. METHODS: Follow-up examinations at a minimum of 3 months postoperatively included uncorrected (UDVA) and corrected (CDVA) distance visual acuity, uncorrected (UIVA) and distancecorrected (DCIVA)) intermediate as well as uncorrected (UNVA) and distance-corrected (DCNVA) near visual acuity. Uncorrected and distance-corrected reading acuity at 40 cm for near, 80 cm for intermediate distance, and at the patient’s preferred near and intermediate distances were evaluated with the reading desk. RESULTS: In this study, 22 eyes of 11 patients having cataract surgery with implantation of the trifocal Finevision IOL were evaluated. Postoperative monocular Snellen median values were 20/21.44 (range 20/52.61 to 20/14.49) for UDVA, 20/20.47 (range 20/38.11 to 20/16.64) for UIVA, and 20/26.39 (range 20/43.76 to 20/18.24) for UNVA. Subjective intermediate distance at the binocular uncorrected examination on the reading desk was 64.2 cm (range 51.9 to 80.0) with a reading acuity of 0.10 logMAR (range 0.32 to 0.00). Subjective near distance at the uncorrected binocular reading desk examination was 36.5 cm (30.8 to 41.2) with a near reading acuity of 0.06 logMAR (range 0.23 to 0.01). The preferred distances differed significantly from the fixed ones of 40 and 80 cm. The preferred intermediate distance was almost consistent, with the intermediate addition of 1.75 D corresponding to 57.1 cm. CONCLUSION: The visual and reading function of the trifocal IOL was better at the patient’s preferred near and intermediate distances. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2015; 41:2707–2714 Q 2015 ASCRS and ESCRS
In the past years, the implantation of multifocal intraocular lenses (IOLs) has gained a particular importance. Many patients undergoing cataract surgery have been seeking simultaneous correction of distance and near vision. In addition, the intermediate distance, which is the distance between 50 and 80 cm, became of special interest since activities such as computer and smartphone use have become increasingly important in everyday life. To meet these expectations, numerous Q 2015 ASCRS and ESCRS Published by Elsevier Inc.
designs of multifocal IOLs1–5 have been developed since the 1980s6,7 for different lifestyles. These include refractive, diffractive, refractive–diffractive,3,8 and apodized–diffractive designs.4,5 Although multifocal IOLs have been known for a decrease in contrast sensitivity9–11 as well as photic phenomena such as halos and glare,12,13 they are still the preferred method for many patients seeking spectacle independence for all distances. While the intermediate distance has been
http://dx.doi.org/10.1016/j.jcrs.2015.06.038 0886-3350
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neglected with many bifocal IOLs, newer bifocal IOLs with a low or a moderate addition14 aimed at improving the intermediate distance. Furthermore, the promising diffractive trifocal IOLs have been designed to generate a third focus for the intermediate distance5 in addition to the far and near foci produced by bifocal IOLs. However, despite the advantage of offering an additional focus for intermediate distance, the distribution of light energy on 3 instead of 2 foci in trifocal IOLs could theoretically compromise the far and near visual acuity. The aim of this study was to evaluate the visual acuity as well as the reading performance at near and intermediate distances after implantation of the diffractive trifocal Finevision IOL (PhysIOL). For determination of the reading acuity, the Salzburg Reading Desk (Figure 1) has been chosen to carry out the measurement under standardized conditions. The reading desk allows the determination of the patient's preferred reading and intermediate distances,15–17 thereby reflecting the foci produced by the IOL. MATERIALS AND METHODS This prospective, nonrandomized, noncomparative clinical trial, following the tenets of the declaration of Helsinki and approved by the local ethics committee of Heidelberg, Germany, was undertaken at the International Vision Correction Research Centre, University Eye Clinic Heidelberg, Heidelberg, Germany. An informed consent was obtained from all the participating patients prior to the examinations. For IOL power calculation, the Holladay formula was used for all the enrolled eyes. Inclusion criteria consisted in the unilateral or bilateral implantation of the IOL, age of more than 18 years, a postoperative expected Snellen visual acuity of 20/40 or better, and the patient's approval to participate in the study. Ocular exclusion criteria included previous ocular surgeries and other ocular pathologiesdexcept for cataractd that could affect the postoperative visual acuity. Other exclusion criteria comprised dementia, pregnancy, and lactation.
Submitted: March 13, 2015. Final revision submitted: May 22, 2015. Accepted: June 17, 2015. From International Vision Correction Research Centre and David J. Apple Laboratory, University Eye Clinic, Heidelberg, Germany. Supported by a grant from the Klaus Tschira Stiftung, Heidelberg, Germany (International Vision Correction Research Centre). Presented at ASCRS (American Society of Cataract and Refractive Surgeons) Boston, Massachusetts, USA, April 2014. Corresponding author: Gerd U. Auffarth, MD, PhD, University Hospital Heidelberg, Department of Ophthalmology, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany. E-mail: gerd.auffarth@ med.uni-heidelberg.de.
Postoperative Examinations The uncorrected as well as the distance-corrected visual acuity were determined using Early Treatment Diabetic Retinopathy Study (ETDRS) charts (Precision Vision) for distance vision at 4 m, for intermediate vision at 80 cm, and for near vision at 40 cm. Monocular as well as binocular examinations were carried out. The reading performance was evaluated using the Salzburg Reading Desk. The examination has been performed at fixed distances of 40 cm for near and 80 cm for intermediate distance. Afterward, the patients were allowed to choose their preferred near and intermediate distances. To evaluate real-life reading performance a binocular examination followed the monocular one.
Reading Desk The Salzburg Reading Desk was developed to attain of standardized measurements of the reading performance and has received the Conformite Europeenne Mark approval in May 2012. In this study, the RDFD 1.0 model was used. The device consists of a laptop computer and a reading desk,8,15–19 which comprises a high-resolution monitor with 2 USB cameras and a microphone. The examination on the reading desk allows standardization of screen illumination, contrast, and inclination. These factors are however adjustable.19 Logarithmically scaled Colenbrander sentences in German language (Precision Vision) are presented to the patients, where a separate measurement is performed for each print size. Tracking of the sound waves allows the calculation of the reading speed in words per minute (wpm). In a healthy eye, a reading speed above or equal to the threshold of 80 wpm is accepted. A stopwatch incorporated in the device records the reading duration which is expressed in seconds. Furthermore, the reading distance is being measured continuously during the whole procedure using video stereophotogrammetry.8,16,17,19 For each separate measurement, the average distance is determined. Reading acuity given in logMAR is calculated by the software with consideration of the reading distance and the print size of the smallest readable sentence with a minimum speed of 80 wpm.
Intra-ocular Lens The Finevision (Figure 2) is an aspheric diffractive trifocal IOL. The design consists of a combination of two diffractive profiles5 with a near addition of 3.5 diopters (D) and 1.75 D, respectively.5,20 The amount of light energy that is allocated to the double convergence of the near addition, that is, the second diffraction order, lies at 7 D for the first profile. For the second profile, the second diffraction order lies at 3.5 D, thus contributing to a reinforcement of the near addition of 3.5 D. Thereby, the energy loss is reduced from 20% known for diffractive bifocal IOLs to 15%.5 Further properties of the IOL are the convolution and the apodization, which help reduce stray light, halos, and glare.5,20 On the one hand, the smoothening of the edges of the diffractive structures, the convolution, leads to a significant reduction in stray light produced at these edges. On the other hand, the decreasing height of the diffractive structures from the center to the periphery, the apodization, allows an increasing amount of light energy assigned to the far focus at the expense of the near and intermediate foci in a dilated pupil.20
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Figure 1. Reading desk.
This is in turn accompanied by a reduction of stray light and glare produced from the out-of-focus image at these 2 foci.9
Statistical Analysis
patient. The significance level a was set to 5%. The linear mixed model was performed using SPSS (version 21, SPSS, Inc.).
RESULTS
The medians (interquartile range [IQR]) were used for the descriptive statistical analysis. Furthermore, the detection of statistical significance between paired samples was performed using the Wilcoxon rank-sum test with a significance level of a Z 5% in the case of the binocular examinations using Medcalc software (version 12.3.0.0, Medcalc Software bvba). For the monocular examinations, a linear mixed model was used to identify the statistical significance between the paired samples by taking into consideration the correlations between the two eyes belonging to the same
Twenty-three eyes of 12 patients with a median age of 66 years (range 55 to 74 years) received the trifocal IOL after cataract extraction by 2 experienced surgeons. Only the binocular implantations, that is, 22 eyes of 11 patients, were included in the statistical analysis. Follow-up examinations took place at a mean of 15.77 G 8.39 months postoperatively. Postoperatively, there has been no statistically significant difference between target and achieved spherical equivalent (mixed model, P Z .594) (Table 1). Twenty eyes (90.9%) were within G0.50 D of emmetropia, whereas 95.5% (21 eyes) were within G0.75 D and 100% (22 eyes) were within G1.0 D. Visual Acuity The increase from the pre-operative median Snellen CDVA of 20/35.58 (range 20/126.19 to 20/25.18) to the postoperative median CDVA of 20/16.26 (range
Table 1. Difference between target and achieved refraction.
Refraction in Target Refraction Achieved D (n Z 22) (Holladay 1) Refraction Median (IQR) Min; Max
C0.01 (0.30) 0.29; C0.49
0.06 (0.34) 0.50; C0.88
Difference Target Versus Achieved Refraction 0.04 (0.30) 0.74; C0.79
IQR Z interquartile range; Min Z minimum; Max Z maximum; D Z diopters.
Figure 2. Trifocal intra-ocular lens 1 year postoperatively. J CATARACT REFRACT SURG - VOL 41, DECEMBER 2015
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Table 2. Visual acuity at far, intermediate, and near distances using ETDRS charts. Visual Acuity [lSnellen 20/] Monocular (n Z 22) Median Min; Max Binocular (n Z 11) Median Min; Max
UDVA (4 m)
CDVA (4 m)
UIVA (80 cm)
DCIVA (80 cm)
DCNVA (40 cm)
DCNVA (40 cm)
21.44 52.61; 14.49
16.26 25.18; 13.21
20.47 38.11; 16.64
17.42 33.19; 12.62
26.39 43.76; 18.24
20.94 39.91; 15.89
17.42 30.27; 13.21
15.89 20.94; 12.62
16.64 34.76; 13.21
13.84 31.70; 13.21
21.93 39.91; 15.89
19.10 39.91; 13.21
UDVA Z uncorrected distance visual acuity; CDVA Z corrected-distance visual acuity; UIVA Z uncorrected intermediate visual acuity; DCIVA Z distancecorrected intermediate visual acuity; DCNVA Z uncorrected near visual acuity; DCNVA Z distance-corrected near visual acuity; Min Z minimum; Max Z maximum. Visual acuity is reported in Snellen format for medians and ranges converted from the logMAR values.
20/25.18 to 20/13.21) was statistically significant (mixed model, P ! .001). Table 2 comprises the monocular and binocular visual acuity results at far, intermediate, and near distances. Visual acuity is reported in Snellen format for medians and ranges converted from the logMAR values according to Holladay. The uncorrected binocular visual acuity was 20/32 or better for 100 % of the eyes (n Z 11) at 4 m and for 90.9 % (n Z 10) of the eyes at 80 cm as well as at 40 cm (Figure 3). With distance-correction a value of 20/32 or better was achieved in 90.9 % of the eyes (n Z 10) at 40 cm and in 100% of the eyes (n Z 11) at 4 m and at 80 cm. Reading Performance The reading acuity at a fixed distance and that at the respective preferred distance showed a statistically significant difference only for the monocular uncorrected near distance examination (mixed model, P Z .013). Table 3 and Table 4 show the individual P values as well as the medians of the values measured on the reading desk. Regarding the tested distances, the differences between each fixed and its respective preferred distances were statistically significant in all cases (mixed model, P ! .05 for the monocular examinations), (Wilcoxon test, P ! .05 for the binocular
Figure 3. Cumulative binocular Snellen visual acuity.
examinations). Figures 4 and 5 illustrate the reading acuity at various distances. Apart from the binocular examinations at near distance with and without distance correction, the smallest readable letter size of all other examinations differed significantly between the measurements at the fixed and at its respective preferred distance (mixed model, P ! .05 for the monocular examinations) (Wilcoxon test, P ! .05 for the binocular examinations). There was no evidence of a statistical significance in terms of the reading speed and the reading duration neither for the monocular examinations (mixed model, P O .05) nor for the binocular examinations (Wilcoxon test, P O .05) (Tables 3 and 4). The statistical comparison between the visual acuity tested with ETDRS charts and the reading acuity measured with the reading desk at the same distances (Table 5) resulted in a difference with a statistical significance except for binocular near distance examinations, both with and without distance correction (Wilcoxon test, P O .05). DISCUSSION For patients pursuing spectacle independence, the principle of a trifocal IOL offers a promising solution. The diffractive trifocal Finevision IOL provides good postoperative intermediate visual acuity with an attempt to reduce the subsequent deterioration of near and distance visual acuity to a minimum by reducing the energy loss.5 In our cohort, the visual acuity is reported in Snellen format for medians and ranges and has been converted from the logMAR values according to Holladay.21,22 In a previous study of Sheppard et al.,20 the binocular defocus curve of the same IOL showed no peak for the intermediate focus but an extended area of a visual acuity of 20/40 or better between C1.0 D and 2.5 D instead with a plateau visual acuity between 1.0 and 2.0 D. Despite generally better results of the defocus curve under photopic conditions, a
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Table 3. Monocular and binocular intermediate distance reading performance with the Salzburg Reading Desk in median.
Uncorrected Intermediate (80 cm) (n Z 22)
Uncorrected Preferred Intermediate (n Z 22)
P Value
Distance-Corrected Intermediate (80 cm) (n Z 22)
Monocular reading performance [Median] Reading acuity 0.24 (IQR: 0.18) 0.21 (IQR: 0.14) .930 0.19 (IQR: 0.20) (logMAR) Smallest readable letter 0.57 (IQR: 0.30) 0.80 (IQR: 0.32) !.001 0.63 (IQR: 0.30) size (log scale) Distance (cm) 79.55 (IQR: 2.57) 62.20 (IQR: 20.03) !.001 79.55 (IQR: 2.15) Reading speed (wpm) 95.50 (IQR: 30.00) 101.5 (IQR: 31.00) .532 100.50 (IQR: 54.50) Reading duration 9.75 (IQR: 2.90) 9.95 (IQR: 2.93) .489 9.85 (IQR: 4.25) (seconds) Binocular reading (n Z 11) (n Z 11) (n Z 10) performance (median) Reading acuity 0.10 (IQR: 0.04) 0.10 (IQR: 0.12) .2500 0.11 (IQR: 0.07) (logMAR) Smallest readable letter 0.80 (IQR: 0.00) 0.80 (IQR: 0.45) .0312 0.80 (IQR: 0.13) size (log scale) Distance (cm) 79.70 (IQR: 1.80) 64.20 (IQR: 13.70) .0078 80.15 (IQR: 2.13) Reading speed (wpm) 98.00 (IQR: 33.50) 113.00 (IQR: 65.50) .3125 116.00 (IQR: 43.00) Reading duration 9.40 (IQR: 3.25) 8.50 (IQR: 4.30) .4687 8.25 (IQR: 3.00) (seconds)
Distance-Corrected Preferred Intermediate (n Z 22)
P Value
0.18 (IQR: 0.16)
.227
0.80 (IQR: 0.37)
!.001
62.80 (IQR: 22.13) 104.00 (IQR: 30.75) 9.20 (IQR: 2.48)
!.001 .768 1.000
(n Z 10) 0.08 (IQR: 0.07)
.5781
1.25 (IQR: 0.45)
.0312
61.50 (IQR: 18.10) 103.00 (IQR: 31.00) 9.15 (IQR: 2.20)
.0156 .4687 .4687
IQR Z interquartile range. Statistical differences were calculated for the monocular examination with the mixed model and for the binocular examination with the Wilcoxon rank-sum test; level of significance: a Z 5%.
significant difference between photopic and mesopic conditions, was only detected at 1.5 D, which corresponds to the intermediate focus. Similarly, Ali o et al.23 detected in their cohort with values of 0.19 G 0.08 logMAR a wide range of improved vision around 1.5 D on the binocular defocus curve. The 6-month monocular visual acuity outcomes of Ali o et al.23 comprised a mean UIVA of 0.20 G 0.11 logMAR and a mean DCIVA of 0.17 G 0.09 logMAR measured in 80 cm. Concurrent results for CDVA and 40 cm DCNVA were 0.05 G 0.06 logMAR and 0.16 G 0.13 logMAR, respectively. Sheppard et al.20 examined distance visual acuity yielding similar results with a monocular UDVA of 0.19 G 0.09 logMAR and a CDVA of 0.08 G 0.08 logMAR. The lower visual acuity of the latter compared with our measurements may be explained by the age group of 69.8 G 10 years (range 52 to 86 years) compared with our cohort with a mean age of 66.18 G 6.28 years (range 55 to 74 years). Another diffractive trifocal IOL is the AT Lisa tri 839MP (Carl Zeiss Meditec), which has been recently introduced. With a near addition of 3.33 D and an intermediate addition of 1.66 D, the preferred near and intermediate distances are expected to be more
distant than those measured for the Finevision IOL. Mojzis et al.24 showed a visual acuity of 0.2 logMAR or better between C1.5 D and 3.0 D on the defocus curve. The visual acuity at the 1.0 D focus was better than that at the 1.5 D focus. At the 6-month followup visit, the examined cohort had a mean UDVA of 0.03 G 0.09 logMAR, a mean UIVA of 0.08 G 0.10 logMAR tested at 66 cm, and a mean UNVA of 0.20 G 0.12 logMAR tested at 33 cm, using modified ETDRS charts.24 In another study performed by Law et al.,25 the reading acuity was evaluated using the Radner Reading Charts. The binocular results with a mean UNVA of 0.16 G 0.07 and a mean DCIVA of 0.16 G 0.07 logRAD confirmed the improved near and intermediate visual acuity through the production of 3 foci by the IOL. The comparison of the intermediate visual acuity measured at 80 cm with the reading acuity tested at the same distance and of the monocular examination of the near visual acuity with the reading acuity in 40 cm resulted in statistically significant differences. The differences between the visual acuity and the reading acuity at the same distances might be caused by counting the number of correct letters on reading ETDRS optotypes, even if some letters have been
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Table 4. Monocular and binocular near distance reading performance with the Salzburg Reading Desk in median.
Uncorrected Near (40 cm) (n Z 22)
Uncorrected Preferred Near (n Z 22)
Monocular reading performance (median) Reading acuity 0.19 (IQR: 0.20) 0.19 (IQR: 0.19) (logMAR) Smallest readable letter 0.63 (IQR: 0.30) 0.72 (IQR: 0.17) size (log scale) Distance (cm) 39.55 (IQR: 2.18) 38.70 (IQR: 5.98) Reading speed (wpm) 99.00 (IQR: 28.50) 96.50 (IQR: 28.00) Reading duration 9.65 (IQR: 1.83) 9.70 (IQR: 2.08) (seconds) Binocular reading (n Z 11) (n Z 11) performance (median) Reading acuity 0.11 (IQR: 0.15) 0.06 (IQR: 0.16) (logMAR) Smallest readable letter 0.80 (IQR: 0.27) 1.00 (IQR: 0.20) size (log scale) Distance (cm) 39.50 (IQR: 2.50) 36.50 (IQR: 4.45) Reading speed (wpm) 101.00 (IQR: 17.50) 93.00 (IQR: 17.00) Reading duration 10.00 (IQR: 1.95) 10.40 (IQR: 2.65) (seconds)
P Value
Distance-Corrected Near (40 cm) (n Z 22)
Distance-Corrected Preferred Near (n Z 22)
P Value
.013
0.14 (IQR: 0.09)
0.11 (IQR: 0.16)
.340
.008
0.72 (IQR: 0.17)
0.80 (IQR: 0.20)
!.001
.008 .419 .737
40.15 (IQR: 1.00) 100.50 (IQR: 38.25) 9.60 (IQR: 3.38)
36.60 (IQR: 4.30) 102.50 (IQR: 30.50) 9.30 (IQR: 2.58)
!.001 .403 .180
(n Z 10)
(n Z 10)
.8438
0.01 (IQR: 0.12)
0.01 (IQR: 0.15)
1.0000
.0625
1.00 (IQR: 0.20)
1.00 (IQR: 0.15)
.0625
.0312 .4375 .6875
40.20 (IQR: 2.03) 124.50 (IQR: 34.00) 8.15 (IQR: 1.95)
36.55 (IQR: 4.55) 90.0 (IQR: 38.25) 10.50 (IQR: 2.45)
.0312 .1250 .0625
IQR Z interquartile range. Statistical differences were calculated for the monocular examination with the mixed model and for the binocular examination with the Wilcoxon rank-sum test; level of significance: a Z 5%.
omitted. However, when reading sentences, skipping a word would slow down the reading process leading to a reduction of the reading speed to values below the threshold of 80 wpm, which represents the threshold for healthy eyes. The examination with the reading desk resulted in medians of the preferred intermediate distance between 61.50 cm and 64.20 cm, whereas medians of the preferred near distance ranged from 36.50 to 38.70 cm. At the preferred distances either the same letter size could be read with a higher reading speed
or a smaller letter size could be read. However, some measurements showed identical or even a lower reading acuity at the preferred distance compared with the respective fixed one. This is caused by consideration of the reading distance for the calculation of the reading acuity. As a consequence, nearly identical reading acuity was achieved at the shorter preferred distances despite the smaller print. In conclusion, the results show that the near and intermediate visual and reading acuity results can be improved by the diffractive trifocal Finevision IOL
Figure 4. Monocular reading acuity at various distances (n Z 22).
Figure 5. Binocular reading acuity at various distances (n Z 11).
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Table 5. Visual acuity with ETDRS charts versus reading acuity with the Salzburg Reading Desk at the same distances. Near Distance Uncorrected monocular examination Distance-corrected monocular examination Uncorrected binocular examination Distance-corrected binocular examination Intermediate distance Uncorrected monocular examination Distance-corrected monocular examination Uncorrected binocular examination Distance-corrected binocular examination
P Value .001 .003 .2783 .0840 !.001 !.001 .0322 .0039
Statistical differences were calculated for the monocular examination with the mixed model and for the binocular examination with the Wilcoxon rank sum-test; level of significance: a Z 5%.
without comprising the distance visual acuity. This in turn enables the patients to perform daily activities in these distances with spectacle independence. The preferred near as well as the intermediate distances tested with the Salzburg Reading Desk significantly differed from the fixed near distance of 40 cm and the fixed intermediate distance of 80 cm, respectively. Emphasis on that fact in postoperative patient education might assist the patients find their best reading distance. WHAT WAS KNOWN The diffractive trifocal provides good intermediate visual acuity by its intermediate focus. WHAT THIS PAPER ADDS The preferred near and intermediate distances with the diffractive trifocal IOL differed from the standard distances examined with ETDRS charts. The results of the reading acuity tested with the reading desk differed from those of the visual acuity tested with ETDRS charts at the same distances. The reading acuity above the threshold of 80 wpm reflects the print size detected easily without effort, thus corresponding to the patient’s daily life, whereas the visual acuity might include single letters of a smaller letter size detected with effort.
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€hren J, Klaproth OK, Titke C, 18. Casagrande M, Baumeister M, Bu Kohnen T. Influence of additional astigmatism on distancecorrected near visual acuity and reading performance. Br J Ophthalmol 2014; 98:24–29 19. Hirnschall N, Motaabbed JK, Dexl A, Grabner G, Findl O. Evaluation of an electronic reading desk to measure reading acuity in pseudophakic patients. J Cataract Refract Surg 2014; 40:1462–1468 20. Sheppard AL, Shah S, Bhatt U, Bhogal G, Wolffsohn JS. Visual outcomes and subjective experience after bilateral implantation of a new diffractive trifocal intraocular lens. J Cataract Refract Surg 2013; 39:343–349 21. Holladay JT, Prager TC. Mean visual acuity [letter]. Am J Ophthalmol 1991; 111:372–374 22. Holladay JT. Proper method for calculating average visual acuity. J Refract Surg 1997; 13:388–391. Available at: http://www. hicsoap.com/publications/ProperMethodforCalculating.pdf. Accessed September 23, 2015 JL, Montalba n R, Pen ~a-Garcıa P, Soria FA, Vega23. Alio Estrada A. Visual outcomes of a trifocal aspheric diffractive intra-
ocular lens with microincision cataract surgery. J Refract Surg 2013; 29:756–761 ~ a-Garcıa P, Liehneova I, Ziak P, Alio JL. Outcomes 24. Mojzis P, Pen of a new diffractive trifocal intraocular lens. J Cataract Refract Surg 2014; 40:60–69 25. Law EM, Aggarwal RK, Kasaby H. Clinical outcomes with a new trifocal intraocular lens. Eur J Ophthalmol 2014; 24:501–508
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First author: Mary S.A. Attia, MD University Eye Clinic, Heidelberg, Germany
Near and intermediate reading performance of a diffractive trifocal intraocular lens using a reading desk Mary S.A. Attia, MD, Gerd U. Auffarth, MD, PhD, Ramin Khoramnia, MD, Katharina Linz, MD, Florian T.A. Kretz, MD
PURPOSE: To evaluate reading performance of a trifocal intra-ocular lens (IOL) at near and intermediate distances using the Salzburg Reading Desk. SETTING: International Vision Correction Research Centre and David J. Apple Laboratory, University Eye Clinic, Heidelberg, Germany. DESIGN: Prospective, nonrandomized clinical study. METHODS: Follow-up examinations at a minimum of 3 months postoperatively included uncorrected (UDVA) and corrected (CDVA) distance visual acuity, uncorrected (UIVA) and distancecorrected (DCIVA)) intermediate as well as uncorrected (UNVA) and distance-corrected (DCNVA) near visual acuity. Uncorrected and distance-corrected reading acuity at 40 cm for near, 80 cm for intermediate distance, and at the patient’s preferred near and intermediate distances were evaluated with the reading desk. RESULTS: In this study, 22 eyes of 11 patients having cataract surgery with implantation of the trifocal Finevision IOL were evaluated. Postoperative monocular Snellen median values were 20/21.44 (range 20/52.61 to 20/14.49) for UDVA, 20/20.47 (range 20/38.11 to 20/16.64) for UIVA, and 20/26.39 (range 20/43.76 to 20/18.24) for UNVA. Subjective intermediate distance at the binocular uncorrected examination on the reading desk was 64.2 cm (range 51.9 to 80.0) with a reading acuity of 0.10 logMAR (range 0.32 to 0.00). Subjective near distance at the uncorrected binocular reading desk examination was 36.5 cm (30.8 to 41.2) with a near reading acuity of 0.06 logMAR (range 0.23 to 0.01). The preferred distances differed significantly from the fixed ones of 40 and 80 cm. The preferred intermediate distance was almost consistent, with the intermediate addition of 1.75 D corresponding to 57.1 cm. CONCLUSION: The visual and reading function of the trifocal IOL was better at the patient’s preferred near and intermediate distances. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2015; 41:2707–2714 Q 2015 ASCRS and ESCRS
In the past years, the implantation of multifocal intraocular lenses (IOLs) has gained a particular importance. Many patients undergoing cataract surgery have been seeking simultaneous correction of distance and near vision. In addition, the intermediate distance, which is the distance between 50 and 80 cm, became of special interest since activities such as computer and smartphone use have become increasingly important in everyday life. To meet these expectations, numerous Q 2015 ASCRS and ESCRS Published by Elsevier Inc.
designs of multifocal IOLs1–5 have been developed since the 1980s6,7 for different lifestyles. These include refractive, diffractive, refractive–diffractive,3,8 and apodized–diffractive designs.4,5 Although multifocal IOLs have been known for a decrease in contrast sensitivity9–11 as well as photic phenomena such as halos and glare,12,13 they are still the preferred method for many patients seeking spectacle independence for all distances. While the intermediate distance has been
http://dx.doi.org/10.1016/j.jcrs.2015.06.038 0886-3350
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neglected with many bifocal IOLs, newer bifocal IOLs with a low or a moderate addition14 aimed at improving the intermediate distance. Furthermore, the promising diffractive trifocal IOLs have been designed to generate a third focus for the intermediate distance5 in addition to the far and near foci produced by bifocal IOLs. However, despite the advantage of offering an additional focus for intermediate distance, the distribution of light energy on 3 instead of 2 foci in trifocal IOLs could theoretically compromise the far and near visual acuity. The aim of this study was to evaluate the visual acuity as well as the reading performance at near and intermediate distances after implantation of the diffractive trifocal Finevision IOL (PhysIOL). For determination of the reading acuity, the Salzburg Reading Desk (Figure 1) has been chosen to carry out the measurement under standardized conditions. The reading desk allows the determination of the patient's preferred reading and intermediate distances,15–17 thereby reflecting the foci produced by the IOL. MATERIALS AND METHODS This prospective, nonrandomized, noncomparative clinical trial, following the tenets of the declaration of Helsinki and approved by the local ethics committee of Heidelberg, Germany, was undertaken at the International Vision Correction Research Centre, University Eye Clinic Heidelberg, Heidelberg, Germany. An informed consent was obtained from all the participating patients prior to the examinations. For IOL power calculation, the Holladay formula was used for all the enrolled eyes. Inclusion criteria consisted in the unilateral or bilateral implantation of the IOL, age of more than 18 years, a postoperative expected Snellen visual acuity of 20/40 or better, and the patient's approval to participate in the study. Ocular exclusion criteria included previous ocular surgeries and other ocular pathologiesdexcept for cataractd that could affect the postoperative visual acuity. Other exclusion criteria comprised dementia, pregnancy, and lactation.
Submitted: March 13, 2015. Final revision submitted: May 22, 2015. Accepted: June 17, 2015. From International Vision Correction Research Centre and David J. Apple Laboratory, University Eye Clinic, Heidelberg, Germany. Supported by a grant from the Klaus Tschira Stiftung, Heidelberg, Germany (International Vision Correction Research Centre). Presented at ASCRS (American Society of Cataract and Refractive Surgeons) Boston, Massachusetts, USA, April 2014. Corresponding author: Gerd U. Auffarth, MD, PhD, University Hospital Heidelberg, Department of Ophthalmology, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany. E-mail: gerd.auffarth@ med.uni-heidelberg.de.
Postoperative Examinations The uncorrected as well as the distance-corrected visual acuity were determined using Early Treatment Diabetic Retinopathy Study (ETDRS) charts (Precision Vision) for distance vision at 4 m, for intermediate vision at 80 cm, and for near vision at 40 cm. Monocular as well as binocular examinations were carried out. The reading performance was evaluated using the Salzburg Reading Desk. The examination has been performed at fixed distances of 40 cm for near and 80 cm for intermediate distance. Afterward, the patients were allowed to choose their preferred near and intermediate distances. To evaluate real-life reading performance a binocular examination followed the monocular one.
Reading Desk The Salzburg Reading Desk was developed to attain of standardized measurements of the reading performance and has received the Conformite Europeenne Mark approval in May 2012. In this study, the RDFD 1.0 model was used. The device consists of a laptop computer and a reading desk,8,15–19 which comprises a high-resolution monitor with 2 USB cameras and a microphone. The examination on the reading desk allows standardization of screen illumination, contrast, and inclination. These factors are however adjustable.19 Logarithmically scaled Colenbrander sentences in German language (Precision Vision) are presented to the patients, where a separate measurement is performed for each print size. Tracking of the sound waves allows the calculation of the reading speed in words per minute (wpm). In a healthy eye, a reading speed above or equal to the threshold of 80 wpm is accepted. A stopwatch incorporated in the device records the reading duration which is expressed in seconds. Furthermore, the reading distance is being measured continuously during the whole procedure using video stereophotogrammetry.8,16,17,19 For each separate measurement, the average distance is determined. Reading acuity given in logMAR is calculated by the software with consideration of the reading distance and the print size of the smallest readable sentence with a minimum speed of 80 wpm.
Intra-ocular Lens The Finevision (Figure 2) is an aspheric diffractive trifocal IOL. The design consists of a combination of two diffractive profiles5 with a near addition of 3.5 diopters (D) and 1.75 D, respectively.5,20 The amount of light energy that is allocated to the double convergence of the near addition, that is, the second diffraction order, lies at 7 D for the first profile. For the second profile, the second diffraction order lies at 3.5 D, thus contributing to a reinforcement of the near addition of 3.5 D. Thereby, the energy loss is reduced from 20% known for diffractive bifocal IOLs to 15%.5 Further properties of the IOL are the convolution and the apodization, which help reduce stray light, halos, and glare.5,20 On the one hand, the smoothening of the edges of the diffractive structures, the convolution, leads to a significant reduction in stray light produced at these edges. On the other hand, the decreasing height of the diffractive structures from the center to the periphery, the apodization, allows an increasing amount of light energy assigned to the far focus at the expense of the near and intermediate foci in a dilated pupil.20
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Figure 1. Reading desk.
This is in turn accompanied by a reduction of stray light and glare produced from the out-of-focus image at these 2 foci.9
Statistical Analysis
patient. The significance level a was set to 5%. The linear mixed model was performed using SPSS (version 21, SPSS, Inc.).
RESULTS
The medians (interquartile range [IQR]) were used for the descriptive statistical analysis. Furthermore, the detection of statistical significance between paired samples was performed using the Wilcoxon rank-sum test with a significance level of a Z 5% in the case of the binocular examinations using Medcalc software (version 12.3.0.0, Medcalc Software bvba). For the monocular examinations, a linear mixed model was used to identify the statistical significance between the paired samples by taking into consideration the correlations between the two eyes belonging to the same
Twenty-three eyes of 12 patients with a median age of 66 years (range 55 to 74 years) received the trifocal IOL after cataract extraction by 2 experienced surgeons. Only the binocular implantations, that is, 22 eyes of 11 patients, were included in the statistical analysis. Follow-up examinations took place at a mean of 15.77 G 8.39 months postoperatively. Postoperatively, there has been no statistically significant difference between target and achieved spherical equivalent (mixed model, P Z .594) (Table 1). Twenty eyes (90.9%) were within G0.50 D of emmetropia, whereas 95.5% (21 eyes) were within G0.75 D and 100% (22 eyes) were within G1.0 D. Visual Acuity The increase from the pre-operative median Snellen CDVA of 20/35.58 (range 20/126.19 to 20/25.18) to the postoperative median CDVA of 20/16.26 (range
Table 1. Difference between target and achieved refraction.
Refraction in Target Refraction Achieved D (n Z 22) (Holladay 1) Refraction Median (IQR) Min; Max
C0.01 (0.30) 0.29; C0.49
0.06 (0.34) 0.50; C0.88
Difference Target Versus Achieved Refraction 0.04 (0.30) 0.74; C0.79
IQR Z interquartile range; Min Z minimum; Max Z maximum; D Z diopters.
Figure 2. Trifocal intra-ocular lens 1 year postoperatively. J CATARACT REFRACT SURG - VOL 41, DECEMBER 2015
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Table 2. Visual acuity at far, intermediate, and near distances using ETDRS charts. Visual Acuity [lSnellen 20/] Monocular (n Z 22) Median Min; Max Binocular (n Z 11) Median Min; Max
UDVA (4 m)
CDVA (4 m)
UIVA (80 cm)
DCIVA (80 cm)
DCNVA (40 cm)
DCNVA (40 cm)
21.44 52.61; 14.49
16.26 25.18; 13.21
20.47 38.11; 16.64
17.42 33.19; 12.62
26.39 43.76; 18.24
20.94 39.91; 15.89
17.42 30.27; 13.21
15.89 20.94; 12.62
16.64 34.76; 13.21
13.84 31.70; 13.21
21.93 39.91; 15.89
19.10 39.91; 13.21
UDVA Z uncorrected distance visual acuity; CDVA Z corrected-distance visual acuity; UIVA Z uncorrected intermediate visual acuity; DCIVA Z distancecorrected intermediate visual acuity; DCNVA Z uncorrected near visual acuity; DCNVA Z distance-corrected near visual acuity; Min Z minimum; Max Z maximum. Visual acuity is reported in Snellen format for medians and ranges converted from the logMAR values.
20/25.18 to 20/13.21) was statistically significant (mixed model, P ! .001). Table 2 comprises the monocular and binocular visual acuity results at far, intermediate, and near distances. Visual acuity is reported in Snellen format for medians and ranges converted from the logMAR values according to Holladay. The uncorrected binocular visual acuity was 20/32 or better for 100 % of the eyes (n Z 11) at 4 m and for 90.9 % (n Z 10) of the eyes at 80 cm as well as at 40 cm (Figure 3). With distance-correction a value of 20/32 or better was achieved in 90.9 % of the eyes (n Z 10) at 40 cm and in 100% of the eyes (n Z 11) at 4 m and at 80 cm. Reading Performance The reading acuity at a fixed distance and that at the respective preferred distance showed a statistically significant difference only for the monocular uncorrected near distance examination (mixed model, P Z .013). Table 3 and Table 4 show the individual P values as well as the medians of the values measured on the reading desk. Regarding the tested distances, the differences between each fixed and its respective preferred distances were statistically significant in all cases (mixed model, P ! .05 for the monocular examinations), (Wilcoxon test, P ! .05 for the binocular
Figure 3. Cumulative binocular Snellen visual acuity.
examinations). Figures 4 and 5 illustrate the reading acuity at various distances. Apart from the binocular examinations at near distance with and without distance correction, the smallest readable letter size of all other examinations differed significantly between the measurements at the fixed and at its respective preferred distance (mixed model, P ! .05 for the monocular examinations) (Wilcoxon test, P ! .05 for the binocular examinations). There was no evidence of a statistical significance in terms of the reading speed and the reading duration neither for the monocular examinations (mixed model, P O .05) nor for the binocular examinations (Wilcoxon test, P O .05) (Tables 3 and 4). The statistical comparison between the visual acuity tested with ETDRS charts and the reading acuity measured with the reading desk at the same distances (Table 5) resulted in a difference with a statistical significance except for binocular near distance examinations, both with and without distance correction (Wilcoxon test, P O .05). DISCUSSION For patients pursuing spectacle independence, the principle of a trifocal IOL offers a promising solution. The diffractive trifocal Finevision IOL provides good postoperative intermediate visual acuity with an attempt to reduce the subsequent deterioration of near and distance visual acuity to a minimum by reducing the energy loss.5 In our cohort, the visual acuity is reported in Snellen format for medians and ranges and has been converted from the logMAR values according to Holladay.21,22 In a previous study of Sheppard et al.,20 the binocular defocus curve of the same IOL showed no peak for the intermediate focus but an extended area of a visual acuity of 20/40 or better between C1.0 D and 2.5 D instead with a plateau visual acuity between 1.0 and 2.0 D. Despite generally better results of the defocus curve under photopic conditions, a
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Table 3. Monocular and binocular intermediate distance reading performance with the Salzburg Reading Desk in median.
Uncorrected Intermediate (80 cm) (n Z 22)
Uncorrected Preferred Intermediate (n Z 22)
P Value
Distance-Corrected Intermediate (80 cm) (n Z 22)
Monocular reading performance [Median] Reading acuity 0.24 (IQR: 0.18) 0.21 (IQR: 0.14) .930 0.19 (IQR: 0.20) (logMAR) Smallest readable letter 0.57 (IQR: 0.30) 0.80 (IQR: 0.32) !.001 0.63 (IQR: 0.30) size (log scale) Distance (cm) 79.55 (IQR: 2.57) 62.20 (IQR: 20.03) !.001 79.55 (IQR: 2.15) Reading speed (wpm) 95.50 (IQR: 30.00) 101.5 (IQR: 31.00) .532 100.50 (IQR: 54.50) Reading duration 9.75 (IQR: 2.90) 9.95 (IQR: 2.93) .489 9.85 (IQR: 4.25) (seconds) Binocular reading (n Z 11) (n Z 11) (n Z 10) performance (median) Reading acuity 0.10 (IQR: 0.04) 0.10 (IQR: 0.12) .2500 0.11 (IQR: 0.07) (logMAR) Smallest readable letter 0.80 (IQR: 0.00) 0.80 (IQR: 0.45) .0312 0.80 (IQR: 0.13) size (log scale) Distance (cm) 79.70 (IQR: 1.80) 64.20 (IQR: 13.70) .0078 80.15 (IQR: 2.13) Reading speed (wpm) 98.00 (IQR: 33.50) 113.00 (IQR: 65.50) .3125 116.00 (IQR: 43.00) Reading duration 9.40 (IQR: 3.25) 8.50 (IQR: 4.30) .4687 8.25 (IQR: 3.00) (seconds)
Distance-Corrected Preferred Intermediate (n Z 22)
P Value
0.18 (IQR: 0.16)
.227
0.80 (IQR: 0.37)
!.001
62.80 (IQR: 22.13) 104.00 (IQR: 30.75) 9.20 (IQR: 2.48)
!.001 .768 1.000
(n Z 10) 0.08 (IQR: 0.07)
.5781
1.25 (IQR: 0.45)
.0312
61.50 (IQR: 18.10) 103.00 (IQR: 31.00) 9.15 (IQR: 2.20)
.0156 .4687 .4687
IQR Z interquartile range. Statistical differences were calculated for the monocular examination with the mixed model and for the binocular examination with the Wilcoxon rank-sum test; level of significance: a Z 5%.
significant difference between photopic and mesopic conditions, was only detected at 1.5 D, which corresponds to the intermediate focus. Similarly, Ali o et al.23 detected in their cohort with values of 0.19 G 0.08 logMAR a wide range of improved vision around 1.5 D on the binocular defocus curve. The 6-month monocular visual acuity outcomes of Ali o et al.23 comprised a mean UIVA of 0.20 G 0.11 logMAR and a mean DCIVA of 0.17 G 0.09 logMAR measured in 80 cm. Concurrent results for CDVA and 40 cm DCNVA were 0.05 G 0.06 logMAR and 0.16 G 0.13 logMAR, respectively. Sheppard et al.20 examined distance visual acuity yielding similar results with a monocular UDVA of 0.19 G 0.09 logMAR and a CDVA of 0.08 G 0.08 logMAR. The lower visual acuity of the latter compared with our measurements may be explained by the age group of 69.8 G 10 years (range 52 to 86 years) compared with our cohort with a mean age of 66.18 G 6.28 years (range 55 to 74 years). Another diffractive trifocal IOL is the AT Lisa tri 839MP (Carl Zeiss Meditec), which has been recently introduced. With a near addition of 3.33 D and an intermediate addition of 1.66 D, the preferred near and intermediate distances are expected to be more
distant than those measured for the Finevision IOL. Mojzis et al.24 showed a visual acuity of 0.2 logMAR or better between C1.5 D and 3.0 D on the defocus curve. The visual acuity at the 1.0 D focus was better than that at the 1.5 D focus. At the 6-month followup visit, the examined cohort had a mean UDVA of 0.03 G 0.09 logMAR, a mean UIVA of 0.08 G 0.10 logMAR tested at 66 cm, and a mean UNVA of 0.20 G 0.12 logMAR tested at 33 cm, using modified ETDRS charts.24 In another study performed by Law et al.,25 the reading acuity was evaluated using the Radner Reading Charts. The binocular results with a mean UNVA of 0.16 G 0.07 and a mean DCIVA of 0.16 G 0.07 logRAD confirmed the improved near and intermediate visual acuity through the production of 3 foci by the IOL. The comparison of the intermediate visual acuity measured at 80 cm with the reading acuity tested at the same distance and of the monocular examination of the near visual acuity with the reading acuity in 40 cm resulted in statistically significant differences. The differences between the visual acuity and the reading acuity at the same distances might be caused by counting the number of correct letters on reading ETDRS optotypes, even if some letters have been
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Table 4. Monocular and binocular near distance reading performance with the Salzburg Reading Desk in median.
Uncorrected Near (40 cm) (n Z 22)
Uncorrected Preferred Near (n Z 22)
Monocular reading performance (median) Reading acuity 0.19 (IQR: 0.20) 0.19 (IQR: 0.19) (logMAR) Smallest readable letter 0.63 (IQR: 0.30) 0.72 (IQR: 0.17) size (log scale) Distance (cm) 39.55 (IQR: 2.18) 38.70 (IQR: 5.98) Reading speed (wpm) 99.00 (IQR: 28.50) 96.50 (IQR: 28.00) Reading duration 9.65 (IQR: 1.83) 9.70 (IQR: 2.08) (seconds) Binocular reading (n Z 11) (n Z 11) performance (median) Reading acuity 0.11 (IQR: 0.15) 0.06 (IQR: 0.16) (logMAR) Smallest readable letter 0.80 (IQR: 0.27) 1.00 (IQR: 0.20) size (log scale) Distance (cm) 39.50 (IQR: 2.50) 36.50 (IQR: 4.45) Reading speed (wpm) 101.00 (IQR: 17.50) 93.00 (IQR: 17.00) Reading duration 10.00 (IQR: 1.95) 10.40 (IQR: 2.65) (seconds)
P Value
Distance-Corrected Near (40 cm) (n Z 22)
Distance-Corrected Preferred Near (n Z 22)
P Value
.013
0.14 (IQR: 0.09)
0.11 (IQR: 0.16)
.340
.008
0.72 (IQR: 0.17)
0.80 (IQR: 0.20)
!.001
.008 .419 .737
40.15 (IQR: 1.00) 100.50 (IQR: 38.25) 9.60 (IQR: 3.38)
36.60 (IQR: 4.30) 102.50 (IQR: 30.50) 9.30 (IQR: 2.58)
!.001 .403 .180
(n Z 10)
(n Z 10)
.8438
0.01 (IQR: 0.12)
0.01 (IQR: 0.15)
1.0000
.0625
1.00 (IQR: 0.20)
1.00 (IQR: 0.15)
.0625
.0312 .4375 .6875
40.20 (IQR: 2.03) 124.50 (IQR: 34.00) 8.15 (IQR: 1.95)
36.55 (IQR: 4.55) 90.0 (IQR: 38.25) 10.50 (IQR: 2.45)
.0312 .1250 .0625
IQR Z interquartile range. Statistical differences were calculated for the monocular examination with the mixed model and for the binocular examination with the Wilcoxon rank-sum test; level of significance: a Z 5%.
omitted. However, when reading sentences, skipping a word would slow down the reading process leading to a reduction of the reading speed to values below the threshold of 80 wpm, which represents the threshold for healthy eyes. The examination with the reading desk resulted in medians of the preferred intermediate distance between 61.50 cm and 64.20 cm, whereas medians of the preferred near distance ranged from 36.50 to 38.70 cm. At the preferred distances either the same letter size could be read with a higher reading speed
or a smaller letter size could be read. However, some measurements showed identical or even a lower reading acuity at the preferred distance compared with the respective fixed one. This is caused by consideration of the reading distance for the calculation of the reading acuity. As a consequence, nearly identical reading acuity was achieved at the shorter preferred distances despite the smaller print. In conclusion, the results show that the near and intermediate visual and reading acuity results can be improved by the diffractive trifocal Finevision IOL
Figure 4. Monocular reading acuity at various distances (n Z 22).
Figure 5. Binocular reading acuity at various distances (n Z 11).
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Table 5. Visual acuity with ETDRS charts versus reading acuity with the Salzburg Reading Desk at the same distances. Near Distance Uncorrected monocular examination Distance-corrected monocular examination Uncorrected binocular examination Distance-corrected binocular examination Intermediate distance Uncorrected monocular examination Distance-corrected monocular examination Uncorrected binocular examination Distance-corrected binocular examination
P Value .001 .003 .2783 .0840 !.001 !.001 .0322 .0039
Statistical differences were calculated for the monocular examination with the mixed model and for the binocular examination with the Wilcoxon rank sum-test; level of significance: a Z 5%.
without comprising the distance visual acuity. This in turn enables the patients to perform daily activities in these distances with spectacle independence. The preferred near as well as the intermediate distances tested with the Salzburg Reading Desk significantly differed from the fixed near distance of 40 cm and the fixed intermediate distance of 80 cm, respectively. Emphasis on that fact in postoperative patient education might assist the patients find their best reading distance. WHAT WAS KNOWN The diffractive trifocal provides good intermediate visual acuity by its intermediate focus. WHAT THIS PAPER ADDS The preferred near and intermediate distances with the diffractive trifocal IOL differed from the standard distances examined with ETDRS charts. The results of the reading acuity tested with the reading desk differed from those of the visual acuity tested with ETDRS charts at the same distances. The reading acuity above the threshold of 80 wpm reflects the print size detected easily without effort, thus corresponding to the patient’s daily life, whereas the visual acuity might include single letters of a smaller letter size detected with effort.
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First author: Mary S.A. Attia, MD University Eye Clinic, Heidelberg, Germany