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Lynn B. Meuleners, Michelle Louise Fraser, Jonathan Ng, Nigel Morlet, The impact of first- and second-eye cataract surgery on injurious falls that require hospitalisation: a whole-population study, Age and Ageing, Volume 43, Issue 3, May 2014, Pages 341–346, https://doi.org/10.1093/ageing/aft177
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Abstract
Background: cataract is a leading cause of reversible vision impairment and may increase falls in older adults.
Objective: to assess the risk of an injury due to a fall among adults aged 60+, 2 years before first-eye cataract surgery, between first-eye surgery and second-eye surgery and 2 years after second-eye surgery.
Design: a retrospective cohort study.
Setting: Western Australian Hospital Morbidity Data System and the Western Australian Death Registry.
Subjects: there were 28,396 individuals aged 60+ years who underwent bilateral cataract surgery in Western Australia between 2001 and 2008.
Methods: Poisson regression analysis based on generalised estimating equations compared the frequency of falls 2 years before first-eye cataract surgery, between first- and second-eye surgery and 2 years after second-eye cataract surgery after accounting for potential confounders.
Results: the risk of an injurious fall that required hospitalisation doubled (risk ratio: 2.14, 95% confidence interval: 1.82 to 2.51) between first- and second-eye cataract surgery compared with the 2 years before first-eye surgery. There was a 34% increase in the number of injurious falls that required hospitalisation in the 2 years after second-eye cataract surgery compared with the 2 years before first-eye surgery (risk ratio: 1.34, 95% confidence interval: 1.16–1.55).
Conclusions: there was an increased risk of injurious falls after first- and second-eye cataract surgery which has implications for the timely provision of second-eye surgery as well as appropriate refractive management between surgeries.
Introduction
Cataract is the leading cause of reversible vision impairment in developed countries and by the age of 70 years, almost everyone will have developed some degree of cataract [1]. Cataract affects several aspects of vision, and may increase the risk of falls in older adults due to reduced balance, stability and hazard detection [2, 3]. Falls are also a leading cause of morbidity in Australia and the leading cause of accidental death in persons aged 65+ years [4]. It is conservatively estimated that 30% of older adults fall each year with 20% of these falls resulting in hospitalisation for injuries [5–7], resulting in over a billion dollars in medical treatment, disability and lost output each year in Australia [8].
The rate of cataract surgery has increased threefold in Australia over the past 20 years [9] and is a highly successful treatment for improving vision and quality of life [10, 11]. However, studies on the impact of cataract surgery on falls have produced conflicting results. A study of older women in the UK reported a 34% reduction in the overall rate of falls during the year after expedited first-eye cataract surgery compared with wait listed surgeries [12].
A smaller study also found a statistically significant reduction in the number of self-reported falls 6 months after surgery [13]. In contrast, another UK study found a non-significant decrease in self-reported falls after the second-eye surgery among a cohort of 239 older women [14] and a prospective study from the USA also found no difference in falls after cataract surgery [15]. However, a recent study reported a 27% increase in hospitalisation for falls in the year after first-eye cataract surgery only [16]. Lastly, a recent Cochrane systematic review concluded that the correction of visual deficiency and its effect on reducing falls still remained unknown [17].
Although cataracts are usually bilateral, cataract surgery is usually performed on one eye at a time [11]. Previous research has found that first-eye cataract surgery brings about significant improvements in visual acuity and contrast sensitivity [10, 11, 18]. However, those with bilateral cataract frequently report vision-related problems while waiting for second-eye surgery, most likely due to differences in vision between the operated and un-operated eyes [10, 11, 19, 20]. Second-eye surgery largely corrects this problem [10, 17]. Since people with bilateral cataract may need to function for substantial periods of time with un-operated cataract before and between cataract surgeries, it is essential to understand the separate effects of first- and second-eye surgery on falls. However previous research has either examined first eye only, combined first, and second eye in the analyses or it has not been specified [12, 13, 15].
The aim of this study was to assess the risk of an injurious fall requiring hospitalisation among adults aged 60+ years in Western Australia between 2001 and 2008 before first eye, between first and second eye, and after second-eye cataract surgery using data from the Western Australian Data Linkage System (WADLS).
Methods
Study design
A whole-population retrospective cohort study was undertaken comparing the number of hospital admissions from injurious falls among adults aged 60+ years in Western Australia 2 years before first eye, between first and second eye and 2 years after second-eye cataract surgery.
Data sources
De-identified data were obtained from the WADLS following ethics approval from Curtin University. The WADLS includes all hospital admissions, birth and death records, mental health service contacts, motor vehicle crash records, cancer registrations and midwives' notifications for all Western Australians [21].
International Classification for Diseases (ICD) codes [22] were used to identify all cataract surgeries in persons with a Western Australian residential postcode from 2001 to 2008: 42698-00, 42702-00, 42702-01, 42698-01, 42702-02, 42702-03, 42698-04, 42702-08, 42702-09, 42698-02, 42702-04, 42702-05, 42698-03, 42702-06, 42702-07, 42731-01, 42698-05, 42702-01, 42702-10, 42702-11.
The cohort comprised those who had bilateral cataract surgery. To ensure that no participant had cataract surgery prior to the study period, all hospital records were extracted and anyone found to have had previous cataract surgery was excluded. The cohort was linked to the Death Registry to identify deaths during the study period, in order to account for a shorter follow-up period.
An injurious fall was recorded if the principal diagnosis for at least one hospital admission in the cataract cohort's record was an ‘injury’, as designated by a diagnosis code between S00.0 and T14.9 (Chapter XIX, ICD-10-AM), with a primary external cause code: W00-W19 (ICD-10-AM [20]; 1 July 1998–2008) from 1999 to 2010.
The extracted demographic information included age, gender, indigenous status, residential location, marital status, socioeconomic status (SES) and the presence of co-morbidities. Residential location was defined as metropolitan, rural or remote based on residential postcode at admission for first-eye cataract surgery. Indigenous was defined as being Aboriginal and/or Torres Strait Islander. Marital status was classified as having a partner (married or de-facto) or not. Comorbidity was the presence of one or more of 17 conditions recorded during any hospital admission in the year prior to first-eye cataract surgery [23].The presence or absence of these co-morbid conditions was used in the analysis. SES was measured using the Socioeconomic Indexes for Areas', Index of Relative Disadvantage and summarised as quintiles at 10, 30, 50 (median), 70 and 90%, with 10% being the lowest and 90% the highest SES level. Age was treated as a categorical variable.
Statistical analysis
Descriptive statistics were used to summarise the cohort. Baseline characteristics of those who had an injurious fall and those who did not were compared using Chi-square tests. The outcome of interest was a hospital admission due to an injurious fall.
Poisson regression analysis based on generalised estimating equations (GEEs) was undertaken to compare the frequency of injurious falls after accounting for potential confounders. To investigate the association of timing of cataract surgery and falls risk, follow-up time was divided into three ‘cataract exposure’ periods of time unique to each individual; the 2 years prior to first-eye cataract surgery, the time between first and second cataract surgery and 2 years after the second cataract surgery. The follow-up was censored accordingly for those who died during the study period.
The GEE approach extends the standard Poisson regression by accommodating the inherent correlation of the data collected at three time points and provides robust standard error estimates. The Poisson GEE analysis was performed using the STATA (version 9) statistical package. Results were considered significant at the 0.05 level.
Results
There were 28,396 individuals aged 60+ years who had bilateral cataract surgery in Western Australia from 2001 to 2008. Of this group, 1,094 (3.85%) people experienced 1,220 injurious falls that required a hospitalization. During the follow-up period, 983 (3.46%) persons experienced one injurious fall, 96 (0.34%) had two injurious falls and 15 (0.06%) persons had three or more injurious falls. A total of 4,944 (17.40%) deaths occurred during the study period.
Demographic characteristics comparing those who had an injurious fall that required hospitalisation with those who did not are shown in Table 1. The majority who fell were over 80 years of age (58.96%), lived in the metropolitan area (71.52%), were not married (56.19%), were non-indigenous (99.4%), reported at least one co-morbidity (75.87%) and were female (75.41%). The average number of co-morbidities was 2.74 (SD = 2.77) for those who fell and 1.58 (SD = 2.47) for those who did not have a fall.
. | All . | No fall . | Fall . | P-value* . |
---|---|---|---|---|
n (%) . | n (%) . | n (%) . | ||
Married** | ||||
Married | 17,770 (64.29) | 17,306 (65.1) | 464 (43.81) | <0.0001 |
Not married | 9,871 (35.71) | 9,276 (34.9) | 595 (56.19) | |
Indigenous | ||||
No | 28,224 (99.39) | 27,136 (99.39) | 1,088 (99.45) | 0.80 |
Yes | 172 (0.61) | 166 (0.61) | 6 (0.55) | |
Gender | ||||
Male | 11,806 (41.58) | 11,537 (42.26) | 269 (24.59) | <0.0001 |
Female | 16,590 (58.42) | 15,765 (57.74) | 825 (75.41) | |
Age | ||||
60–64 | 1,958 (6.9) | 1,939 (7.1) | 19 (1.74) | <0.0001 |
65–69 | 3,864 (13.61) | 3,820 (13.99) | 44 (4.02) | |
70–74 | 6,184 (21.78) | 6,062 (22.2) | 122 (11.15) | |
75–79 | 7,936 (27.95) | 7,672 (28.1) | 264 (24.13) | |
80–84 | 5,860 (20.64) | 5,501 (20.15) | 359 (32.82) | |
85+ | 2,594 (9.14) | 2,308 (8.45) | 286 (26.14) | |
Resident** | ||||
Urban | 19,979 (70.61) | 19,198 (70.58) | 781 (71.52) | 0.70 |
Regional | 6,346 (22.43) | 6,112 (22.47) | 234 (21.43) | |
Rural | 1,968 (6.96) | 1,891 (6.95) | 77 (7.05) | |
SES** | ||||
0(lowest) | 5,880 (20.93) | 5,669 (20.99) | 211 (19.43) | 0.005 |
1 | 5,528 (19.68) | 5,316 (19.68) | 212 (19.52) | |
2 | 5,942 (21.15) | 5,744 (21.27) | 198 (18.23) | |
3 | 5,393 (19.2) | 5,142 (19.04) | 251 (23.11) | |
4 (highest) | 5,351 (19.05) | 5,137 (19.02) | 214 (19.71) | |
Co-morbidity | ||||
No | 14,084 (49.6) | 13,820 (50.62) | 264 (24.13) | <0.0001 |
Yes | 14,312 (50.4) | 13,482 (49.38) | 830 (75.87) |
. | All . | No fall . | Fall . | P-value* . |
---|---|---|---|---|
n (%) . | n (%) . | n (%) . | ||
Married** | ||||
Married | 17,770 (64.29) | 17,306 (65.1) | 464 (43.81) | <0.0001 |
Not married | 9,871 (35.71) | 9,276 (34.9) | 595 (56.19) | |
Indigenous | ||||
No | 28,224 (99.39) | 27,136 (99.39) | 1,088 (99.45) | 0.80 |
Yes | 172 (0.61) | 166 (0.61) | 6 (0.55) | |
Gender | ||||
Male | 11,806 (41.58) | 11,537 (42.26) | 269 (24.59) | <0.0001 |
Female | 16,590 (58.42) | 15,765 (57.74) | 825 (75.41) | |
Age | ||||
60–64 | 1,958 (6.9) | 1,939 (7.1) | 19 (1.74) | <0.0001 |
65–69 | 3,864 (13.61) | 3,820 (13.99) | 44 (4.02) | |
70–74 | 6,184 (21.78) | 6,062 (22.2) | 122 (11.15) | |
75–79 | 7,936 (27.95) | 7,672 (28.1) | 264 (24.13) | |
80–84 | 5,860 (20.64) | 5,501 (20.15) | 359 (32.82) | |
85+ | 2,594 (9.14) | 2,308 (8.45) | 286 (26.14) | |
Resident** | ||||
Urban | 19,979 (70.61) | 19,198 (70.58) | 781 (71.52) | 0.70 |
Regional | 6,346 (22.43) | 6,112 (22.47) | 234 (21.43) | |
Rural | 1,968 (6.96) | 1,891 (6.95) | 77 (7.05) | |
SES** | ||||
0(lowest) | 5,880 (20.93) | 5,669 (20.99) | 211 (19.43) | 0.005 |
1 | 5,528 (19.68) | 5,316 (19.68) | 212 (19.52) | |
2 | 5,942 (21.15) | 5,744 (21.27) | 198 (18.23) | |
3 | 5,393 (19.2) | 5,142 (19.04) | 251 (23.11) | |
4 (highest) | 5,351 (19.05) | 5,137 (19.02) | 214 (19.71) | |
Co-morbidity | ||||
No | 14,084 (49.6) | 13,820 (50.62) | 264 (24.13) | <0.0001 |
Yes | 14,312 (50.4) | 13,482 (49.38) | 830 (75.87) |
*P-values from the Chi-square test.
**Missing information.
. | All . | No fall . | Fall . | P-value* . |
---|---|---|---|---|
n (%) . | n (%) . | n (%) . | ||
Married** | ||||
Married | 17,770 (64.29) | 17,306 (65.1) | 464 (43.81) | <0.0001 |
Not married | 9,871 (35.71) | 9,276 (34.9) | 595 (56.19) | |
Indigenous | ||||
No | 28,224 (99.39) | 27,136 (99.39) | 1,088 (99.45) | 0.80 |
Yes | 172 (0.61) | 166 (0.61) | 6 (0.55) | |
Gender | ||||
Male | 11,806 (41.58) | 11,537 (42.26) | 269 (24.59) | <0.0001 |
Female | 16,590 (58.42) | 15,765 (57.74) | 825 (75.41) | |
Age | ||||
60–64 | 1,958 (6.9) | 1,939 (7.1) | 19 (1.74) | <0.0001 |
65–69 | 3,864 (13.61) | 3,820 (13.99) | 44 (4.02) | |
70–74 | 6,184 (21.78) | 6,062 (22.2) | 122 (11.15) | |
75–79 | 7,936 (27.95) | 7,672 (28.1) | 264 (24.13) | |
80–84 | 5,860 (20.64) | 5,501 (20.15) | 359 (32.82) | |
85+ | 2,594 (9.14) | 2,308 (8.45) | 286 (26.14) | |
Resident** | ||||
Urban | 19,979 (70.61) | 19,198 (70.58) | 781 (71.52) | 0.70 |
Regional | 6,346 (22.43) | 6,112 (22.47) | 234 (21.43) | |
Rural | 1,968 (6.96) | 1,891 (6.95) | 77 (7.05) | |
SES** | ||||
0(lowest) | 5,880 (20.93) | 5,669 (20.99) | 211 (19.43) | 0.005 |
1 | 5,528 (19.68) | 5,316 (19.68) | 212 (19.52) | |
2 | 5,942 (21.15) | 5,744 (21.27) | 198 (18.23) | |
3 | 5,393 (19.2) | 5,142 (19.04) | 251 (23.11) | |
4 (highest) | 5,351 (19.05) | 5,137 (19.02) | 214 (19.71) | |
Co-morbidity | ||||
No | 14,084 (49.6) | 13,820 (50.62) | 264 (24.13) | <0.0001 |
Yes | 14,312 (50.4) | 13,482 (49.38) | 830 (75.87) |
. | All . | No fall . | Fall . | P-value* . |
---|---|---|---|---|
n (%) . | n (%) . | n (%) . | ||
Married** | ||||
Married | 17,770 (64.29) | 17,306 (65.1) | 464 (43.81) | <0.0001 |
Not married | 9,871 (35.71) | 9,276 (34.9) | 595 (56.19) | |
Indigenous | ||||
No | 28,224 (99.39) | 27,136 (99.39) | 1,088 (99.45) | 0.80 |
Yes | 172 (0.61) | 166 (0.61) | 6 (0.55) | |
Gender | ||||
Male | 11,806 (41.58) | 11,537 (42.26) | 269 (24.59) | <0.0001 |
Female | 16,590 (58.42) | 15,765 (57.74) | 825 (75.41) | |
Age | ||||
60–64 | 1,958 (6.9) | 1,939 (7.1) | 19 (1.74) | <0.0001 |
65–69 | 3,864 (13.61) | 3,820 (13.99) | 44 (4.02) | |
70–74 | 6,184 (21.78) | 6,062 (22.2) | 122 (11.15) | |
75–79 | 7,936 (27.95) | 7,672 (28.1) | 264 (24.13) | |
80–84 | 5,860 (20.64) | 5,501 (20.15) | 359 (32.82) | |
85+ | 2,594 (9.14) | 2,308 (8.45) | 286 (26.14) | |
Resident** | ||||
Urban | 19,979 (70.61) | 19,198 (70.58) | 781 (71.52) | 0.70 |
Regional | 6,346 (22.43) | 6,112 (22.47) | 234 (21.43) | |
Rural | 1,968 (6.96) | 1,891 (6.95) | 77 (7.05) | |
SES** | ||||
0(lowest) | 5,880 (20.93) | 5,669 (20.99) | 211 (19.43) | 0.005 |
1 | 5,528 (19.68) | 5,316 (19.68) | 212 (19.52) | |
2 | 5,942 (21.15) | 5,744 (21.27) | 198 (18.23) | |
3 | 5,393 (19.2) | 5,142 (19.04) | 251 (23.11) | |
4 (highest) | 5,351 (19.05) | 5,137 (19.02) | 214 (19.71) | |
Co-morbidity | ||||
No | 14,084 (49.6) | 13,820 (50.62) | 264 (24.13) | <0.0001 |
Yes | 14,312 (50.4) | 13,482 (49.38) | 830 (75.87) |
*P-values from the Chi-square test.
**Missing information.
The results of the univariate Chi-square tests found that gender (P < 0.0001), marital status (P < 0.0001), age at first cataract surgery (P < 0.0001) and comorbidity status (P < 0.0001) were significantly associated with an injurious fall (Table 1). Indigenous status (P = 0.80) and residential location (P = 0.70) were not associated with an injurious fall, while SES was marginally associated with falls. The mean time between first- and second-eye cataract surgery was 10.4 months (SD = 16.54) with 46.71% of falls occurring in the first 5 months after first-eye cataract surgery.
Table 2 presents the results of the adjusted multivariate Poisson GEE analysis. The risk of an injurious fall that required hospitalisation doubled between first- and second-eye cataract surgery compared with the 2 years before first-eye cataract surgery [risk ratio (RR): 2.14, 95% confidence interval (CI): 1.82–2.51]. There was a significant 34% increase in an injurious fall that required hospitalisation in the 2 years after bilateral cataract surgery compared with the 2 years before first-eye cataract surgery (RR: 1.34, 95% CI: 1.16–1.55). Being female (RR: 2.24, 95% CI: 1.91–2.63) and having at least one comorbidity (RR: 2.84, 95% CI: 2.46–3.29) significantly increased the risk of an injurious fall that required hospitalisation. There was a progressive increase of an injurious fall with increasing age, with the risk in those aged 85+ years almost seven times (95% CI: 3.93–11.93) than that of the 60–64 years age group. Those who were married (RR: 0.30, 95% CI: 0.60–0.80) had a reduced risk of an injurious fall that required hospitalisation.
. | Adjusted risk ratio . | 95% confidence interval . | P-value . |
---|---|---|---|
Interval | |||
Before first eye | 1.00 | ||
Between first and second eye | 2.14 | 1.82–2.51 | <0.0001 |
After second eye | 1.34 | 1.16–1.55 | <0.0001 |
Gender | |||
Male | 1.00 | ||
Female | 2.24 | 1.91–2.63 | <0.0001 |
Married+ | |||
Not married | 1.00 | ||
Married | 0.70 | 0.60–0.80 | <0.0001 |
Age | |||
60–64 | 1.00 | ||
65–69 | 1.10 | 0.59–2.04 | 0.76 |
70–74 | 1.67 | 0.95–2.94 | 0.07 |
75–79 | 2.56 | 1.47–4.44 | <0.001 |
80–84 | 4.25 | 2.45–7.36 | <0.0001 |
85+ | 6.84 | 3.93–11.93 | <0.0001 |
Co-morbidity | |||
No | 1.00 | ||
Yes | 2.84 | 2.46–3.29 | <0.0001 |
. | Adjusted risk ratio . | 95% confidence interval . | P-value . |
---|---|---|---|
Interval | |||
Before first eye | 1.00 | ||
Between first and second eye | 2.14 | 1.82–2.51 | <0.0001 |
After second eye | 1.34 | 1.16–1.55 | <0.0001 |
Gender | |||
Male | 1.00 | ||
Female | 2.24 | 1.91–2.63 | <0.0001 |
Married+ | |||
Not married | 1.00 | ||
Married | 0.70 | 0.60–0.80 | <0.0001 |
Age | |||
60–64 | 1.00 | ||
65–69 | 1.10 | 0.59–2.04 | 0.76 |
70–74 | 1.67 | 0.95–2.94 | 0.07 |
75–79 | 2.56 | 1.47–4.44 | <0.001 |
80–84 | 4.25 | 2.45–7.36 | <0.0001 |
85+ | 6.84 | 3.93–11.93 | <0.0001 |
Co-morbidity | |||
No | 1.00 | ||
Yes | 2.84 | 2.46–3.29 | <0.0001 |
. | Adjusted risk ratio . | 95% confidence interval . | P-value . |
---|---|---|---|
Interval | |||
Before first eye | 1.00 | ||
Between first and second eye | 2.14 | 1.82–2.51 | <0.0001 |
After second eye | 1.34 | 1.16–1.55 | <0.0001 |
Gender | |||
Male | 1.00 | ||
Female | 2.24 | 1.91–2.63 | <0.0001 |
Married+ | |||
Not married | 1.00 | ||
Married | 0.70 | 0.60–0.80 | <0.0001 |
Age | |||
60–64 | 1.00 | ||
65–69 | 1.10 | 0.59–2.04 | 0.76 |
70–74 | 1.67 | 0.95–2.94 | 0.07 |
75–79 | 2.56 | 1.47–4.44 | <0.001 |
80–84 | 4.25 | 2.45–7.36 | <0.0001 |
85+ | 6.84 | 3.93–11.93 | <0.0001 |
Co-morbidity | |||
No | 1.00 | ||
Yes | 2.84 | 2.46–3.29 | <0.0001 |
. | Adjusted risk ratio . | 95% confidence interval . | P-value . |
---|---|---|---|
Interval | |||
Before first eye | 1.00 | ||
Between first and second eye | 2.14 | 1.82–2.51 | <0.0001 |
After second eye | 1.34 | 1.16–1.55 | <0.0001 |
Gender | |||
Male | 1.00 | ||
Female | 2.24 | 1.91–2.63 | <0.0001 |
Married+ | |||
Not married | 1.00 | ||
Married | 0.70 | 0.60–0.80 | <0.0001 |
Age | |||
60–64 | 1.00 | ||
65–69 | 1.10 | 0.59–2.04 | 0.76 |
70–74 | 1.67 | 0.95–2.94 | 0.07 |
75–79 | 2.56 | 1.47–4.44 | <0.001 |
80–84 | 4.25 | 2.45–7.36 | <0.0001 |
85+ | 6.84 | 3.93–11.93 | <0.0001 |
Co-morbidity | |||
No | 1.00 | ||
Yes | 2.84 | 2.46–3.29 | <0.0001 |
Discussion
This was the first population-based study to examine the association between first- and second-eye cataract surgery and the number of injurious falls that required hospitalisation in bilateral cataract patients. The prevalence of injurious falls during the study period was 3.85%.This is much lower than a recent study which found that almost 28% of falls among older people resulted in an injury, with 18% requiring hospitalisation [2].We found more than a twofold significant increase of injurious falls that required hospitalisation after first-eye surgery (while waiting for second-eye surgery), compared with the 2-year period prior to first-eye cataract surgery. While the number of injurious falls that required hospitalisation was also 34% higher after second-eye cataract surgery compared with before first-eye surgery, this risk was less than during the waiting period between first- and second-eye surgery.
The data linkage methodology has the advantage of reduced selection bias, minimal loss to follow-up, and examination of the problem at the whole-population level [19]. It also has the advantage of detecting small differences by inclusion of large number of cases as well as high-quality, objective data, which can be more accurate than self-reported information [19]. The data from the WADLS represented the most severe cases of injurious falls that required hospitalisation and may underestimate the overall risk of falling. The available data also did not capture lifestyle factors, refractive management, other co-existing ocular pathologies or specific measures of visual function, so we were not able to determine which aspects of visual function may have been associated with an increased number of falls. The lack of a suitable comparison group was a further limitation of the study, although our ‘before and after’ design using the same person as their own control took account of inter-individual differences that can confound studies using separate control groups. We were also not able to determine whether the patients lived independently or were in residential care.
Previous studies have produced conflicting results on whether cataract surgery reduces the incidence of injurious falls [12–14]. First-eye surgery has been shown to bring about significant improvements in visual acuity, contrast sensitivity and stereopsis [10, 11, 18]. Our previous study [16] examined the risk of injury due to a fall in an older population who required one eye cataract surgery only from 2004 to 2008. We found the risk for a fall increased by 27% after first-eye surgery [16]; less than this study of bilateral cataract surgeries. The differences in results may be due to bilateral cataract patients frequently reporting vision-related problems while waiting for second-eye surgery, most likely due to differences in vision between the operated and un-operated eyes [10, 11, 19, 20]. When this difference is large, it can negatively impact on stereopsis (depth perception) [11], which was shown to be important for safe negotiation around objects [24] and for reducing the risk of falls among older people [25]. Ophthalmologists work hard to avoid anisometropia (unequal refractive power between eyes) using biometry to tailor the strength of the intraocular lens implant. However, the eyes may be out of balance until after second-eye surgery has been completed. It is also possible that some of our cohort may have delayed obtaining new glasses until after their second surgery due to the cost of prescription glasses. This meant they had to cope with uncorrected refractive error during the waiting period between surgeries, which increased their risk of falling. Future research should differentiate between these two groups as the risks may be different.
Second-eye cataract surgery can bring about large improvements in stereopsis [10, 19], yet we found a 34% increase in falls compared with the 2 years before first-eye cataract surgery. The risk, however, was considerably lower than after first-eye cataract surgery. Almost half of injurious falls that occurred during the period between first- and second-eye surgery, occurred in the first 5 months after first-eye surgery, and provides preliminary evidence for expedited second-eye cataract surgery in people with bilateral cataract.
Past research has also identified a strong link between physical activity and risk of falls in the older population. Certain types of physical activity increase the risk of a fall by displacing a person's centre of gravity, exposing them to risky environmental factors or inducing fatigue [26, 27]. There is minimal research examining physical activity levels throughout the different stages of cataract surgery; however, cataract surgery was shown to increase confidence and possibly risk taking behaviour [12, 14]. It is possible that patients may be more physically active following cataract surgery compared with the period before first-eye surgery when poor vision may lead them to be more cautious. Therefore, a thorough understanding of the impact of physical activity throughout the cataract process may be essential to understanding falls risk for older adults before, between and after cataract surgery.
Reasons for the differences in results between the current study and the RCTs conducted by Harwood et al. [12] and Foss et al. [14] examining first- and second-eye cataract surgery and falls risk are not clear. However, we examined only hospitalisation falls while Harwood et al. [12] and Foss et al. [14] included all self-reported falls. It should also be noted that our study included a younger age group and both males and females in the sample.
Most of the cohort who had an injurious fall were women and is consistent with previous research [6]. The current study also has confirmed that those who are older are at an increased risk of falling due to their advanced age and fragility [28, 29]. The decreasing frequency in the risk of a fall after second-eye surgery may imply adaptation to the new vision however the increasing frequency of falls over the cataract surgery process may be related to the ageing process. In this study, the cohort who experienced a fall had more co-morbid conditions than those who did not fall. It is also possible that those who are older may also be taking medications, use mobility appliances or have problems with balance and gait [13, 27], which we were not able to determine using the WADLS. We were also not able to determine the cognitive status of those who were hospitalised for a fall. The mechanism for falls risk for older people with cataract is multifactorial and a large prospective cohort study is warranted to better clarify the determinants of risk not possible using the linked databases such as activity levels and refractive problems.
The results of this study have relevance for ophthalmologists when discussing cataract surgery with patients. Those with bilateral cataract should be warned of a potential increased risk of falling following first-eye surgery. Patients should also be advised of the importance of second-eye surgery to correct remaining visual impairment and appropriate refractive management between surgeries.
These findings have implications for the timely provision of second-eye cataract surgery for older adults and provide the impetus for policy changes, given the growing number of older people with bilateral cataract.
Increased risk of fall between first- and second-eye surgery may be related to differences in vision between both eyes.
The decreasing frequency in the risk of a fall after second-eye surgery may imply adaptation to the new vision.
Increasing frequency of falls over the cataract process may be related to the ageing process.
Authors' contribution
All authors contributed extensively to the work presented in this paper. LM: study design, conduct of the project, analysis and drafting of the manuscript. MF: study design and writing of the manuscript. JN and NM: study design and manuscript revision.
Conflicts of interest
None declared.
Funding
This work was supported by the Australian Research Council Discovery Grant (#11010390).
Comments
Cataracts are a leading cause of reversible vision impairment worldwide, most often affecting older adults. Cataract surgeries have typically not been performed on both eyes during the same session due to fears of complications which may compromise vision in both eyes. Instead, surgeries are often done sequentially, in two separate sessions, to reduce the risk of binocular visual impairment due to surgical complications.
Age-related decline in vision has also been associated with increased risk for falls. Through analysis of comparative data between first eye and second eye cataract surgeries, the current study reports that the risk of fall-related injuries to be significantly decreased after surgery in the second eye, presumably relating to reduced depth perception after monocular cataract extraction.
Similar to previously published work, these results tell us that timing of cataract surgeries can be very important. It is important for surgeons to encourage patients to have their second eye surgery performed early to reduce risk of falls, and to be particularly careful in their activities in the period between first- and second-eye surgeries. Indeed, it may be necessary to refer high risk patients to effective post- operative vision rehabilitation program. Another consideration is that, with advances in technology and surgical techniques leading to reduced surgical and post-operative complications, bilateral cataract extraction-- where both eyes are operated on in a single sitting--may be a preferred alternative to reduce falls risks in this context. Bilateral surgery additionally saves money and the time for patients and healthcare systems, and leads to faster recovery of binocular vision.
The linked health databases used in the study have strengths and weaknesses. One strength is access to health records representing the general public -- allowing for researchers to conduct large studies that would be much more difficult and costly if participants had to be recruited. A weakness of the current study, however, is that information gleaned from anonymous records does not extend far beyond the recording of surgeries or falls. An important factor that would be useful to include, and could influence interpretation of the results, would be the number of times a participant fell before the first cataract surgery, since a previous fall is itself a known risk factor for recurrent falls.
The current study confirms previous research findings regarding risk factors for falls among the elderly, such as age, gender, marital status, existing medical conditions, and taking multiple medications. With the rapidly growing elderly population in the US, UK, Canada and around the globe, cataract surgeries are becoming an increasingly common clinical procedure, and we need to be aware of the potential adverse effects such as increased falls risk. Based on such knowledge, we can move towards bringing necessary changes to surgical practice guidelines in an evidence- based manner that maximizes quality of life and cost effectiveness.
Conflict of Interest:
None declared
We certainly agree with the authors that the impact of second eye cataract surgery in falls in the elderly, however, remains inconclusive, in keeping with findings from two other systematic reviews (1). However, evidence suggests that second eye cataract surgery results in significant improvement of binocular clinical outcomes, such as stereoacuity, stereopsis, and ansiometropia. In our recent systematic review we also found some evidence that driving ability improves after second eye cataract surgery (1).
A major limitation in the studies that examined cataract surgery and falls in the elderly is that it was exclusively based a sample of elderly women and was methodologically weak (2). Therefore, benefit of second eye cataract surgery requires more methodologically-sound studies with comparable outcomes, since second eye cataract surgery was found to improve visual functions that are associated with mobility, such as stereoacuity and stereopsis (3, 4, 5). Further, future studies should include population-representative samples of both men and women, and employ falls measures that are less subject to bias (1).
When RCTs and population based studies focus on narrow patient age groups or exclude important segments of the population, it may be difficult to generalize the results (1). An adequately powered trial is strongly encouraged in order to detect clinically important effects on the rate of fall-related injuries after cataract surgery (2). It is also our proposal that future studies should be better designed to control all possible confounding factors including environmental risk factors potential for elderly falls. In addition, future studies designed to evaluate outcomes of cataract surgery (in one or both eyes) should strictly follow the guidelines set forth by Williams, Moutray and Jackson (1, 6).
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Conflict of Interest:
None declared