Second-eye surgery represents a substantial part of the total cataract surgery volume. Desai and coauthors1 report that 35% of 18 454 cataract extractions performed at the end of 1997 in centers in the United Kingdom were second-eye operations. In Sweden, 28.4% of the cataract surgery volume (N = 31 679) in 1992 was second-eye surgery.2 In 1999, this number increased to 36.8% of the total volume (N = 57 362).
There are several reasons for the increasing frequency of second-eye surgery. According to Laidlaw et al.,3 the aging population and major advances in the surgical and anesthetic techniques used in cataract surgery are 2 important reasons for wider indications for surgery and the increase in second-eye surgery. Several reports point to disabilities caused by 1-sided cataract or cataract in the fellow eye after first-eye surgery. Disturbed motion perception4 and disturbed stereo acuity5 may be caused by poor or absent binocular function resulting from cataract in 1 eye. Furthermore, a recent study6 reports that disturbances from the fellow eye and anisometropia are 2 frequent reasons patients report more perceived difficulties after first-eye surgery than before surgery. According to Elliott and coauthors,7 second-eye surgery may be important to improve mobility orientation and avoid falls. Thus, according to the literature, many patients may benefit from cataract extraction in both eyes.
The Swedish National Cataract Register (NCR) was instituted in January 1992. Since its start, the NCR has covered about 93% of all cataract extractions performed in Sweden. Second-eye surgery and visual acuity in the fellow eye are 2 variables that have been collected since the start of the NCR. Table 1 lists these variables for each year since 1995. Since 1995, the NCR has organized a yearly surgical cataract outcomes study,8,9 with an average of 35 clinics participating during a 1-month period each year.
In this study, we analyzed the benefit of first- and second-eye surgery in comparable groups of patients using the NCR database.
Patients and methods
All clinics affiliated with the NCR are invited to participate in a yearly surgical cataract outcomes study.8,9 This study includes all patients operated on during the month of March. Participating clinics are also invited to use the Catquest questionnaire for patients included in the March outcomes study. The evaluation of Catquest outcomes has been described.8
The Catquest responses are evaluated using a decision model. Briefly, an improvement in perceived disabilities, cataract symptoms, and activity level is called a very good benefit; improvement in perceived disabilities and cataract symptoms, a good benefit; improvement in perceived disabilities only, a moderate benefit; status quo in perceived disabilities, a questionable benefit; deterioration in perceived disabilities, no benefit. Data from the 1-month outcomes studies for 1995 to 1999 are stored in the NCR's database.
Complete outcomes data including completed Catquest questionnaires before and 6 months after surgery were available for 8595 patients having surgery in only 1 eye during the 6-month period. They represented consecutive patients having cataract extraction in March at 49 participating surgical units.
Demographic data for the included patients are shown in Table 2. The number of patients who completed the Catquest was lower than the number of patients with follow-up data in the outcomes study. The 3 main reasons were that the patient had (1) mental problems or problems understanding the Swedish language, (2) an incomplete postoperative questionnaire, or (3) cataract extraction in the fellow eye during follow-up. The majority of excluded patients had not completed the postoperative questionnaire (Table 3).
All statistical evaluations were done using the Statistical Package for the Social Sciences for Microsoft Windows (release 8.0). The association between 2 independent samples was studied using the chi-square test when there were 2 categorical variables (eg, sex, first- or second-eye surgery, comorbidity). The association between preoperative variables and first- or second-eye surgery was evaluated using logistic regression analysis. Tests of significance for ranked data (benefit level, satisfaction with vision) for 2 independent groups (first- or second-eye surgery) were analyzed using the Mann-Whitney U test.
The outcomes as defined by Catquest for patients having first- and second-eye surgery are shown in Table 4. The satisfaction with vision as defined by Catquest for both groups of patients is shown in Table 5.
Significant variables for patients having first- and second-eye surgery are shown in Table 6. The most significant difference was in visual acuity in the fellow eye. There was also a difference in mean age and in the disability score sum. Because of the highly significant difference in visual acuity in the fellow eye, the material was subgrouped by visual acuity in the fellow eye.
In 1300 patients, visual acuity in the fellow eye was 1.0 before and after surgery. In this group, there was a difference in the occurrence of an ocular comorbidity between first- and second-eye surgery patients (P < .001, chi-square). However, there was no difference in the preoperative disability score sum (P = .645, Mann-Whitney U test). Therefore, 1043 patients with no ocular comorbidity in the eye to be operated on and a visual acuity of 1.0 in the fellow eye before and after surgery (Subgroup 1) were studied more closely. The outcomes as defined by Catquest in these patients are shown in Table 7A, and satisfaction with vision is shown in Table 7B. For both variables, there was a significantly better patient benefit after second-eye surgery than after first-eye surgery. The evaluation of the outcomes as defined by Catquest was based on 3 areas. The changes in these areas and in visual acuity in the operated eye are shown in Table 8. There were highly significant differences between first- and second-eye patients in the postoperative disability score sum and cataract symptom score sum.
In Subgroup 2, patients had a visual acuity of 0.4 to 0.5 in the fellow eye before and after surgery. In this group, there was a significant difference in the occurrence of ocular comorbidity between first-eye surgery and second-eye surgery patients (P < .001, chi-square) but no significant difference in the preoperative disability score sum (P = .067, Mann-Whitney U). The outcomes as defined by Catquest for patients with no ocular comorbidity in the eye to be operated on and with a visual acuity in the fellow eye of 0.4 to 0.5 before and after surgery are shown in Table 9A. The outcomes in patients having second-eye surgery was significantly better than in those having first-eye surgery. Satisfaction with vision after surgery in both groups is shown in Table 9B. Patients having second-eye surgery were significantly more satisfied with their vision postoperatively. The preoperative visual acuity in the eye to be operated on was significantly better in patients having first-eye surgery (P = .007, Mann-Whitney U) as the median preoperative visual acuity in the eye to be operated on was 0.3 versus 0.2 in patients having second-eye surgery. The postoperative visual acuity in the operated eye was slightly but significantly better in the first-eye patients (P < .001, Mann-Whitney U), with a median value of 0.8 versus 0.7 in second-eye patients.
In Subgroup 3, patients had a visual acuity in the fellow eye of 0.1 or worse before and after surgery. This subgroup consisted of 639 patients. Logistic regression analysis showed that the occurrence of an ocular comorbidity in the eye to be operated on differed significantly (P < .001) between patients scheduled for first-eye surgery and those scheduled for second-eye surgery. In 217 patients, there was no ocular comorbidity in the eye to be operated on and visual acuity in the fellow eye was 0.1 at best before and after surgery. In this group of patients, 186 were scheduled for first-eye surgery and 31 for second-eye surgery. The outcomes as defined by Catquest showed that more patients having first-eye surgery had a very good benefit outcome than patients having second-eye surgery (46.2% versus 32.3%) but also had a higher frequency of a no benefit outcome (6.5% versus 3.2%) (Table 10A). Satisfaction with vision was significantly higher in the first-eye surgery group (Table 10B) (P = .023, Mann-Whitney U). A good visual outcome (0.8 or better) in the operated eye was more frequent in first-eye patients (59.2% versus 35.5%) (P = .026, Mann-Whitney U).
The study design in this analysis of the self-assessed outcomes of first- and second-eye cataract extraction in patients reported to the Swedish NCR was an observational one of consecutive cases. This means that the findings are not based on randomized material.
Furthermore, several originally included patients were excluded during the follow-up. Earlier studies show that patients excluded because of incompletely filled out questionnaires were older, had more diseases, and needed more help than those who completed the questionnaires.8 Thus, the results in patients completing both questionnaires may be better than in all operated patients including nonresponders. For each year, an increasing number of patients having first-eye surgery were excluded from analysis because of surgery in the fellow eye during follow-up. This was especially apparent during 1998 and 1999, probably indicating a reduced waiting time for second-eye surgery.
Second-eye surgery in general resulted in better self-assessed visual functional outcomes than first-eye surgery. The difference in outcomes as defined by Catquest was most evident at the highest (very good) benefit level, and a higher percentage of patients having second-eye surgery perceived improvement in 3 areas: difficulties in performing daily life activities, cataract symptoms such as glare, and daily life activity level. Thus, after surgery in both eyes, the self-assessed visual function included not only relief from difficulties in performing daily life activities but also from disturbing cataract symptoms as well as an increased activity level. This seems to agree with findings in other studies showing better stereo acuity,5 motion perception,4 and mobility orientation7 after surgery in both eyes. A less pronounced improvement (moderate benefit) was found at a higher frequency in first-eye surgery patients. This means that an improvement only in difficulties in performing daily life activities was more frequent in first-eye patients. Any improvement as defined by Catquest (very good benefit + good benefit + moderate benefit) was found in equal frequency in the first- and second-eye patients.
To equalize as much as possible the preoperative conditions, we created 3 subgroups of some included patients. Patients in each group had the same visual acuity in the fellow eye before and after surgery with no known ocular comorbidity. Still, this was an observational study.
Our results can be summarized as follows: Second-eye surgery led to better self-assessed outcomes than first-eye surgery when visual acuity in the fellow eye was good (1.0) or intermediate (0.4 to 0.5). The better outcomes after second-eye surgery than after first-eye surgery, even when visual acuity in the fellow eye was 1.0 before and after surgery, may raise questions. Therefore, this group was analyzed in more detail. In Subgroup 1 (visual acuity 1.0 in fellow eye), visual acuity in the operated eye was on average significantly better preoperatively in patients having second-eye surgery. There was no difference in visual acuity between the first- and second-eye groups after surgery. Thus, the improvement in vision was greater when the first eye was operated on, but patient satisfaction was greater after surgery in the second eye. It can be concluded therefore that patients having second-eye surgery improved more than patients having first-eye surgery in all 3 areas determining the outcome in different benefit levels as defined by Catquest.8 This difference contributed to the difference in outcomes outlined in Table 7A.
The patients in Subgroup 2 (visual acuity 0.4 to 0.5 in fellow eye) were more satisfied after second-eye surgery than after first-eye surgery even though visual acuity was somewhat worse after surgery than in those having surgery in their first eye.
In patients with poor visual acuity in the fellow eye (0.1 at best), the outcomes as defined by Catquest were about the same for first-eye surgery as for second-eye surgery. However, patients having first-eye surgery were more satisfied with their vision. As only 31 patients in this subgroup had second-eye surgery, conclusions must be drawn with caution. First-eye surgery resulted in a visual acuity of 0.8 or more in 59.2%, while after second-eye surgery the visual acuity was 0.8 or better in significantly fewer patients (35.5%). This may in part explain the difference in the patients' satisfaction after surgery.
Our findings cannot be generalized for 2 reasons. First, ours was an observational study. Second, all patients having second-eye surgery had also requested second-eye surgery. All reports in the literature of the benefits of second-eye surgery, including a randomized study,3 are of patients requesting second-eye surgery or listed for second eye-surgery.
Nevertheless, our results can be used for reference when evaluating candidates for second-eye surgery. In most cases, the self-assessed functional outcome was very good after surgery in the second eye. Compared to first-eye surgery, this means significantly less difficulty in performing daily life activities, significantly fewer disabilities caused by cataract symptoms, and an improved activity level in daily life. If the visual outcome after first-eye surgery is poor (0.1 or worse), there is still a good chance of improved self-assessed visual function after second-eye surgery; in our study, 32.3% achieved a very good benefit and only 3.2% achieved no benefit. Furthermore, as many as 54.0% of patients in our study perceived fewer difficulties in performing daily life activities. However, the satisfaction with vision was much lower in patients with a poor visual result after first-eye surgery than in those having a good visual outcome. This difference in outcomes can be a useful adjunct when counseling patients who request second-eye surgery.
The self-assessed functional outcome and satisfaction with vision as defined by Catquest were better after second-eye surgery than after first-eye surgery in comparable groups of patients. Differences in outcome and satisfaction with vision were dependent on preoperative conditions. The results can be used as a reference by surgeon when counseling patients facing second-eye surgery. Most patients with cataract in the second eye who request second-eye surgery should be offered this procedure as it further increases the quality of their health.
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