Extended long-term outcomes of cataract surgery

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1 Extended long-term outcomes of cataract surgery Eva I. Mo nestam and Britta Lundqvist Department of Clinical Sciences Ophthalmology, Norrlands University Hospital, Umea, Sweden ABSTRACT. Purpose: To longitudinally report the changes in visual acuity (VA) and subjective visual function, 10 years after cataract surgery. Methods: This population-based prospective study reviewed 335 patients (85% of survivors) who underwent cataract surgery during a 1-year period in , 289 of whom were also re-examined. The patients underwent a routine eye examination and answered the same visual function questionnaire (VF-14), preoperatively, 4 months postoperatively, 5 years and 10 years after surgery. Results: Ten years after surgery, the best corrected VA (BCVA) of the operated eye had deteriorated to a median of 0.06 (logmar) (Snellen acuity: 20 23) from (logmar) (20 22) postoperatively (p = 0.001). More than two-thirds of the patients had <0.1 logmar units worsening of BCVA compared with postoperatively. Approximately half of the patients had no deterioration in subjective visual function, and 77% had 10 points decline or less. Twelve per cent of the patients (42 335) had a worsening of more than 30 points. Effect size was calculated for the VF-14 total score at all three occasions of follow-up after surgery and was largest approximately 4 months postoperatively. Long-time follow-up of 10 years shows still moderate effect size. Conclusion: These results confirm the effectiveness of cataract extraction, offering good long-term visual rehabilitation for the majority of the patients. The most common cause for large functional loss after 10 years is age-related macular degeneration. Key words: cataract surgery longitudinal outcome study long-term outcome populationbased Acta Ophthalmol. 2012: 90: ª 2011 The Authors Acta Ophthalmologica ª 2011 Acta Ophthalmologica Scandinavica Foundation doi: /j x Introduction Cataract is an important reversible cause of visual impairment in the elderly, and cataract extraction is one of the most frequently performed surgical procedures worldwide (Cugati et al. 2006; Obstbaum 2006). Although cataract surgery is considered cost effective (Cugati et al. 2006; Lansingh et al. 2007), the total cost for society is substantial, as a result of the large number of operations performed. From a health-economic point of view, it is therefore important to assess the outcome for a procedure of this magnitude. Function and quality of life are the outcomes of treatment that are most critical and applicable to the patient. Loss of visual function in the elderly is associated with several adverse implications for health and well-being, such as diminished quality of life, decline in physical and mental functioning, work and academic underperformance, depression, reduced social interaction, increased frequency of falls and fractures, loss of driving ability and loss of independence leading to institutionalization (Brown 1999; Coleman et al. 2004; Harwood et al. 2005; Knudtson et al. 2005; Klein et al. 2006). Visual impairment leads to increased direct and indirect costs at the individual level, as well as to increased costs to the health care systems (Hennis et al. 2009). Therefore, there are clear benefits for interventions that prevent or delay vision loss, such as cataract surgery. From the individual patient s aspect, it is important to analyse the long-term results, as many patients have a remaining life span of several years or decades after cataract surgery. We previously reported 5-year follow-up with satisfactorily outcome both regarding visual acuity and visual functional outcomes (Lundqvist & Mo nestam 2006). Longer follow-up data than 5 years are necessary also in the preoperative counselling of cataract surgery patients. To date, there are few longitudinal, prospective population-based studies published that have extended beyond 5 and 10 years after cataract surgery. The purpose of this report was to longitudinally investigate the 10-year outcome of cataract surgery focusing on changes in self-estimated visual function and visual acuity (VA) over 651

2 time. A comparison was made with preoperative and postoperative results from the same patients 10 years previously. Methods Patients The study included 335 patients who had cataract surgery 10 years previously. All patients were part of a prospective population-based cohort study initiated in Details regarding this cohort, inclusion and exclusion criteria and 5-year results have previously been published (Mo nestam & Wachtmeister 2001; Mo nestam et al. 2005; Lundqvist & Mo nestam 2006). In brief, 810 patients were included, and 395 (49%) patients of these were still alive 10 years after surgery. Sixty patients (15%) did not participate in the follow-up; of these, 41 (10%) suffered from dementia, 11 (3%) could not be located, and 8 (2%) refused. Of the 335 patients included in the 10-year follow-up, 289 (86%) also underwent a clinical eye examination. The major reason for not participating with the examination was trouble unwillingness to travel to the clinic, either because of illness or reluctance to long-distance travelling. Comparisons between participants and nonparticipants at the 10-year follow-up are presented in Table 1. The institutional review board of Umeå University approved the study, which followed the tenets of the Declaration of Helsinki. Informed consent was obtained from all participants at the beginning of each examination. Examinations pre- and postoperatively, and 5 and 10 years after surgery A few weeks before surgery, presenting (PVA) and best corrected visual acuity (BCVA) were measured with a Monoyer Granstro m VA chart, and the patients had a dilated routine eye examination. Presenting visual acuity is the distance visual acuity using the patient s habitual correction, if any. The presence of any ocular comorbidity or past surgery was recorded. Approximately 4 8 weeks postoperatively, the VA test and the eye examination were repeated. Each follow-up examination 5 and 10 years after surgery of the participants was performed in the same Table 1. Comparison of baseline characteristics for the participants examined and those participating with questionnaire only. p-value refers to the differences between those examined and those with questionnaire only. p-values in boldface are statistically significant (p < 0.05). Baseline characteristics manner as the examinations at baseline, except that Early Treatment Diabetic Retinopathy Study (ETDRS) VA charts were used. Age was defined as the age at cataract surgery. The questionnaire Eye examination, n = 289 (73% of survivors) The questionnaire used was based on the VF-14 questionnaire, which is a well-validated instrument to assess visual function, mostly used analysing Questionnaire only, n =46 (12% of survivors) p-value Mean age (years) (95% CI) 67.9 ( ) 72.0 ( ) Age at surgery (years) < Female gender (%) Preoperative BCVA operated eye: n (%) or better 13 (5) (30) 13 (28) (30) 18 (39) < (35) 15 (33) 1.07 ( ) 1.15 ( ) logmar (95% CI) Median (Q1:Q3) 0.7 ( ) 1.0 ( ) Postoperative BCVA 1 2 months after surgery for the operated eye: n (%) or better 242 (84) 34 (74) (4) 2 (4) (7) 4 (9) (2) 3 (6.5) < (3) 3 (6.5) logmar (95% CI) 0.13 ( ) 0.22 ( ) Median (Q1:Q3) (0 0.01) (0 0.22) BCVA 5 years after surgery, operated eye: n (%) or better (66) 21 (46) (12) 5 (11) (8) 0 < (4) 5 (11) 16 (6) 6 (13) Missing cases: n (%) 12 (4) 9 (19) logmar (95% CI) 0.19 ( ) 0.33 ( ) Median (Q1:Q3) 0.04 (0 0.22) 0.11 ( ) BCVA 10 years after surgery, operated eye: n(%) or better 189 (65) (11) (9) (5) < (9) logmar (95% CI) 0.26 ( ) Median (Q1:Q3) 0.06 () ) CI = confidence interval, BCVA = best corrected visual acuity, logmar = logarithm of the minimum angle of resolution, Q1:Q3 = first quartile: third quartile. cataract surgery outcome (Bilbao et al. 2009). It was developed in the USA and has been found appropriate for use also in Europe (Alonso et al.1997). The VF-14 is a measure of functional capacity related to vision based on 14 vision-dependent activities performed in everyday life that can be affected by cataract. An overall estimate of the visual function (The VF-14 score) can be calculated and was in the present study calculated as detailed by 652

3 Steinberg et al. (1994). The range of the VF-14 score is A score of 0 denotes a very low visual function as a result of visual impairment, and 100 points represent unrestricted unaffected subjective ability to perform the 14 vision-dependent activities included. The same questionnaire was answered a few weeks before surgery, 3 4 months after surgery, 5 years after surgery and 10 years after surgery. Type of surgery The type of surgery performed was in 99% a sutureless clear corneal phacoemulsification with temporal incision, and insertion of a foldable intraocular lens (IOL). Ninety-five per cent of the patients ( ) had an Alcon MA60BM Ò IOL implanted, and 3% had a nonfoldable PolyMethyl Meta- Acrylate (PMMA) IOL. None of the patients had an anterior chamber lens. During surgery, 15 patients had posterior capsule rupture (4.5%), nine of whom also vitreous loss (2.7%). Statistical methods When the Monoyer Granstro m letter chart was used, the VA values were converted into a log scale using the method outlined by Holladay & Prager (1991). When using the ET- DRS-chart at 5 and 10 years after surgery, VA was scored as the total number of letters read correctly and expressed as logarithm of the minimum angle of resolution (logmar) units. Patients with failure to read any letters were tested using counting fingers (CF), hand movements (HM) and light perception (P). For VA less than CF 0.5 m, the following arbitrary logmar values were used: CF in front of the eye = logmar 2.2, HM = logmar 2.5 and no light perception = logmar 3 in a similar manner as previously used (Lundqvist &Mo nestam 2006). Changes in BCVA were calculated by subtracting BCVA values 10 years after surgery from the postoperative BCVA values, a positive value indicating worse VA after surgery. The same method was used for calculating change in VF-14 total score, but a positive value indicates improved visual function. Independent sample t-tests were used to compare age differences between groups. Yate s corrected chi-square tests were used to analyse the two-by-two tables, when appropriate. The distribution of postoperative BCVA scores was skewed towards lower logmar values (better VA); therefore, nonparametric Mann Whitney U-tests were used when analysing all BCVA variables, even though BCVA at 5 and 10 years after surgery was normally distributed. Wilcoxon signed ranks test was used to analyse the longitudinal change in BCVA postoperatively versus 10 years after surgery. Correlations were assessed with Pearson s correlation statistics (r P ). Univariate anova analyses were used to control for age. Effect sizes were calculated for VF- 14 total score postoperatively, and after 5 and 10 years. Effect size is the difference between postoperative score and the preoperative score divided by the SD of the score before surgery (Kazis et al. 1989). Cohen s benchmarks were used to classify the magnitude of effect sizes: <0.2, not significant; , small; , moderate and >0.8 large (Cohen 1992). All tests were two-sided, and p-values <0.05 were considered statistically significant. Statistical analyses were performed using the spss (Statistical Package for the Social Sciences for MS Windows, SPSS Inc., Chicago, IL) software 17.0 Results Questionnaire data were obtained from 335 patients, 289 of whom also attended the eye examination, which included visual acuity tests. Baseline characteristics are shown in Table 1. These data were also analysed for the 60 surviving participants not followed (data not shown). No significant differences were found compared with the participating patients, except that the patients not followed were more likely to be older (p < 0.000, independent sample t-tests). The proportion of females was lower among those 335 who participated, but this difference was not significant (p = 0.38). At surgery in , 27% (89 335) of the patients had second eye surgery, i.e. 73% underwent first eye surgery. Five years after surgery, 71% (238 of 335 patients) had undergone cataract surgery on both their eyes. An additional 36 patients (11%) had cataract extraction in their fellow eye between 5 and 10 years after surgery. Ten years after surgery, 61 (18%) patients remained with an unoperated fellow eye. Twenty-six of these had no cataract in the fellow eye, five were not examined, 19 had significant cataract of varying degree, and 11 patients had various types of comorbidity, four of whom had no useful vision in the fellow eye and therefore no indication of cataract surgery. Longitudinal changes in BCVA of the operated eye There was a highly significant correlation between PVA and BCVA of the operated eye 10 years after surgery (r P = 0.66; p < 0.000, Pearson s correlation statistics). Mean PVA was four letters lower than mean BCVA. Because of this small difference, only BCVA data are shown. Best corrected VA, 5 years after surgery of the operated eye, was lower in the questionnaire-only group of patients (borderline statistically significant p = 0.05 Mann Whitney U-tests; Table 1). After adjustment for the significantly older age of these patients, this borderline significance was not sustained (p = 0.89). For the total group of patients, the BCVA of the operated eye deteriorated from a median of (Snellen acuity; 20 22) postoperatively to 0.06 (20 23), 10 years after surgery (p = 0.001; Table 1). The longitudinal change in BCVA between a few months postoperatively and 10 years after surgery was calculated, and Table 2 shows the distribution. In most patients, there was little or no longitudinal change in BCVA of the operated eye between postoperatively and 10 years after surgery. More than two-thirds of the patients had <0.1 logmar units worsening of BCVA in their operated eye. The corresponding percentage for the better seeing eye was 80%. Nine per cent of the patients (26 289) had worse BCVA of the operated eye 10 years after surgery compared to before cataract surgery, i.e. before the operation. Eighty-nine per cent ( ) had better, and 2% had unchanged BCVA. 653

4 Table 2. Distribution of longitudinal change in BCVA between 1 and 2 months postoperatively and 10 years after surgery. Change in BCVA Operated eye Better seeing eye Unchanged or better; no total (%) (50) (58) Worsening 0.1 logmar units or less; no total (%) (19) (22) Between 0.11 and 0.2 logmar units worse; no total (%) (10) (7) Between 0.21 and 0.3 logmar units worse; no total (%) (5) (4) Worsening of 0.31 logmar units or more; no total (%) (16) (9) BCVA = best corrected visual acuity, logmar = logarithm of the minimum angle of resolution. Longitudinal changes in subjective visual function (VF-14 total score) Figure 1 shows box-plot graphs of the distribution of the VF-14 total score preoperatively, postoperatively, 5 and 10 years after surgery for the 335 patients participating with the questionnaire. Before surgery, the median VF-14 total score was 79.5 (mean 74.7; CI = ) and increased to 100 postoperatively (mean 93.5; CI = ). Five years after surgery, the median score was 97.9 (mean 90.9; CI = ) and had at 10 years after surgery decreased to 96.4 (mean 85.7; CI = ). The distribution of longitudinal change in VF-14 score from postoperatively to 10 years after surgery is shown in Table 3. Approximately half of the patients had no deterioration in subjective visual function, and 77% had 10 points in decline or less. Twelve per cent of the patients (42 335) had a deterioration of more than 30 points. Figure 2 shows the distribution of comorbidities causing the worsening in the 31 patients with more than 40 points loss of VF-14 total score. Longitudinal change in effect sizes for cataract surgery Effect sizes were calculated for the VF-14 total score at all three occasions of follow-up after surgery; i.e. postoperatively, 5 years after surgery, and 10 years after surgery (Table 4). The effect size was largest approximately 4 months postoperatively. Long-time follow-up shows moderate effect sizes. Discussion Longitudinal follow-up of this population-based cohort has provided the opportunity to document the 10-year VF-14 pre-op VF-14 post-op VF-14 5 years VF years Fig. 1. Boxplots showing the distribution of VF-14 total score preoperatively, postoperatively, 5 and 10 years after surgery for the 335 patients participating with the questionnaire 10 years after surgery. The boxes include 50% of measured values (between the 25th and 75th percentiles) and show the position of the median (horizontal line) The error bars indicate 1.5 times the interquartile distance from the upper and lower box edges; preop = before surgery, postop = 4 months after surgery. Table 3. Distribution of longitudinal change in VF-14 from postoperatively to 10 years after surgery. Number of patients (%) No deterioration 165 (49) points decline 93 (28) points decline 26 (8) points decline 9 (3) points decline 11 (3) More than 40 points 31 (9) decline 335 (100) subjective and objective visual outcome after cataract surgery. To the authors knowledge, this study provides the first estimate of effect sizes for cataract surgery, from postoperatively to 10 years after surgery in the same population. Generally, our data demonstrate satisfactory results. Both BCVA and VF-14 total score show a longitudinal decline from postoperatively to 10 years after surgery, but in the context of the fact that the patients are 10 years older, these results also at 10 years must be considered excellent from a health-economic point of view. The calculated effect size is still considered moderate, 10 years after surgery (Table 4) (Cohen 1992). We have not been able to find a similar study published, but there are population-based cohort studies investigating long-term change in visual acuity. Klein et al. (2006) found in a 15-year longitudinal study that more than 60% of the eyes with improved vision were as a direct result of cataract extraction. Another longitudinal study on the very elderly showed that subjects who had previously undergone cataract surgery maintained a significantly better BCVA than patients not operated and that more than three-quarters of previously operated subjects maintained a visual acuity of or better at 82 years of age (Bergman et al. 2004). The short-time improvement of cataract surgery (BCVA 4 months postoperatively) was consistent with previous reports, suggesting our results are applicable to other populations, at least in the industrialized world (Desai et al. 1999; Rosen et al. 2005). Ocular disease involving the macula was the largest overall contributor to reduced visual acuity and reduced 654

5 subjective visual function. Eighteen of the 31 patients (58%) with the most severe reduction of VF-14 total score had macular degeneration as the primary cause (Fig. 2). This number is in concordance with our 5-year report in which 60% of the patients with a decline in VF-14 score of 20 or more had macular degeneration. Thompson et al. (2004) found, in their 2-year follow-up, that ocular disease involving the macula was the largest overall contributor to reduced VA with 30% of their subjects affected. Our much higher percentage is probably caused by analysing patients with the largest subjective functional worsening over 5 and 10 years, and not the percentage of macular degeneration found in the total patient group. In the literature, there is considerable controversy whether cataract surgery can promote age-related macular degeneration (ARM) progression. Several studies have supported the hypothesis that the long-term risk of developing above all late, but also early, ARM is higher in cataract surgical eyes (Klein et al. 2002; Freeman et al. 2003; Krishnaiahn et al. 2005). Cugati et al. (2006) suggest there is an increased relatively long-term risk for early ARM to proceed to late stages Macular degeneration (58%) Macular degeneration and glaucoma (13%) Glaukoma (3%) Retinal detachmen (3%) Diabetic retinopathy (3%) Unknown (3%) Bullous keratopathy (3%) Bullous keratopathy and macular degeneration (13%) Fig. 2. Circle diagram showing the distribution of comorbidity responsible for the patients with more than 40 points loss of VF-14 total score over 10 years. after cataract surgery. It is recommended that indications for cataract surgery need to be more stringent than at present, particularly for patients with signs indicating a high risk of progression to late ARM. On the other hand, there are reports that cannot confirm such observations (Armbrecht et al. 2003; Chew et al. 2009). The present study was not designed to evaluate this issue which needs further investigation. Longer follow-up studies can be criticized because technology that is no longer state of the art is compared with the newest option. We believe this is not a major problem of the present study, as foldable hydrophobic IOLs were used in most cases. The only difference compared with cataract surgery of today at our clinic is that the incision size has decreased from 3.2 to 2.2 mm and that IOLs are implanted using injectors and not forceps. Previous research has shown that patients who had surgery in both eyes had greater improvement in functional status and were significantly more satisfied with their visual function than patients who had surgery in only one eye (Castells et al. 1999, 2006). This can explain that more than 80% of the patients had undergone bilateral cataract surgery in the present study. Strengths of this longitudinal study include its population-based design with follow-up at three different timepoints with a high participation rate, at all examinations. All surgical procedures were performed at a single institution, and only four surgeons were involved. We do not believe that variations in technique may account for some of the findings. The same questionnaire (the VF-14) was used to enable direct comparisons between the follow-up points. This questionnaire has been found highly responsive that supports its usefulness for capturing visual change after cataract removal (Bilbao et al. 2009). Our findings should be interpreted in the context of several limitations. Among the potential bias of a prospective cohort study is the selective unavailability for follow-up. In our study, the percentage of subjects who were alive, but did not participate in the 10-year follow-up questionnaire, was 15% of the total group. These patients were on average older. The main reason for not participating was dementia comprising two-thirds of nonparticipants. Dementia precludes participation with a questionnaire and in many cases also visual acuity measurements. Actual refusals were only eight patients (2%). It does not seem that incomplete follow-up has appreciably biased the results. Although the VF-14 questionnaire has been found to be an appropriate instrument for capturing clinically important changes after cataract surgery, the VF-14 exhibits ceiling effects postoperatively (Bilbao et al. 2009). More than half of the patients had a VF-14 total score of 100, 4 months after surgery. This bias is reduced by the longitudinal design of the study, as the patients are compared with themselves. Also, the ceiling effect is less pronounced at 5 and 10 years after surgery. Table 4. Effect sizes for VF-14 total score after cataract surgery at all occasions of follow-up. Postop versus preop 5-years versus preop 10-years versus preop Questionnaire change score (95% CI) 18.7 ( ) 16.2 ( ) 11.0 ( ) Composite score VF-14 before surgery; 74.6 (21.5) CI: (21.5) CI: (21.5) CI: mean (SD) (95% CI) Effect size (95% CI) 0.87 ( ) 0.75 ( ) 0.51 ( ) Postop = 4 months postoperatively, Preop = preoperatively, CI = confidence interval, SD = standard deviation. 655

6 In conclusion, long-term follow-up is an important step in evaluating cataract surgery outcome. Patients with significant cataract can be advised that the visual prognosis in most cases is favourable also 10 years after cataract surgery. ARM degeneration was the most common cause of pronounced deterioration in visual function. Acknowledgements Presented at the EVER meeting (European Association for Vision and Eye Research) at Crete October Grants from Crown Princess Margareta s Committee for the Blind, Stockholm, Sweden, The Swedish Medical Society, Stockholm, Sweden, and from the Västerbottens County Council Research Fund, Umeå, Sweden, are acknowledged. The authors have no proprietary interest in the development or marketing of any product mentioned and do not receive grants from any company. References Alonso J, Espallargues M, Andersen TF et al. (1997): International applicability of the VF-14; an index of visual function in patients with cataracts. 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Br J Ophthalmol 88: Received on August 31st, Accepted on January 28th, Correspondence: Eva Mo nestam, MD, PhD Department of Clinical Sciences Ophthalmology Umeå University S Umeå Sweden Tel: Fax: eva.monestam@vll.se 656