Prevalence of second-eye cataract surgery and time interval after first-eye surgery in Iran: a clinic-based study.

PURPOSE: To determine the prevalence of second-eye senile cataract surgery (SECS) as a proportion of all senile cataract surgeries and the trend in the interval between first and second cataract operations in a main referral and academic eye hospital.
MATERIALS AND METHODS: In this cross-sectional study, a list of patients who underwent senile cataract surgery over four consecutive years (2006-2009) was retrieved from hospital computer-based records as the sampling frame. With a systematic random method, 15% of records were selected (1,585 out of 10,517 records).
RESULTS: First- and second-eye operations were performed in 1,139 (71.9%; 95% confidence interval [CI], 69.5-74.1) and 446 eyes (28.1%; 95% CI, 25.9-30.35), respectively. The proportion of SECS procedures increased from 24.3% in 2006 to 33.4% in 2009 (P = 0.017). The median (interquartile range) interval between the two operations was 9 (4-24) months, which remained stable during the study period. The SECS rate was 10.4% higher (P = 0.01) and the time interval was 13 months shorter (P = 0.007) in patients who underwent phacoemulsification than extracapsular cataract extraction.
CONCLUSION: The number of cataract operations in this tertiary eye care setting increased 1.5 fold over the study period. The proportion of second-eye operations also rose from 1/4 to 1/3 during the same time.

INTRODUCTION

Cataract is known to be the leading cause of avoidable blindness in the world and is responsible for 75% of all blindness cases.1 In recent years, the number of cataract operations has increased globally, which is partly related to an increase in the rate of second-eye cataract surgery (SECS).2–5

Second-eye cataract surgery improves visual capacity, general health status, and patient’s satisfaction.6–11 However, in countries with insufficient capacity for cataract surgery, allocating more services to first-eye cataract procedures instead of second-eye procedures has been recommended to optimize utility in the population.12 Considering the importance of cataract surgery and its effect on reducing blindness rates, it seems that more creative approaches are necessary to address inequities in surgical coverage.13

Cataract is the leading cause of visual impairment in Iran and is responsible for 31.7% of blindness and 47.5% of severe visual impairment.14 The cataract surgical rate in Iran increased about 2.5 times from 526 to 1331 procedures per million over 5 years (2000-2005).15 As there were no data available about SECS in our country or region (the Middle East), we investigated the proportion of SECS and the interval between second and first cataract operations among the clients of one of the main eye care providers in the capital city.

MATERIALS AND METHODS

This cross-sectional study was performed in Labaafinejad, an academic and referral eye hospital. A list of all senile cataract operations over four consecutive years (2006-2009) was retrieved from hospital computer-based records as the sampling frame. The study was approved by the Ethics Committee of Shahid Beheshti Medical University.

With a systematic random method, 15% of records were selected. Patients’ demographic data were collected, and the type of surgery (phacoemulsification [PE] or extracapsular cataract extraction [ECCE]), date of operation, order of operated eye (first- or second-eye), and the interval between first- and second-eye operations were assessed.

The records were extracted using diagnostic codes of the International Classification of Diseases, 10th Revision (ICD-10).16 The selected codes were H25.0 through H25.9 (diagnosis codes for senile cataract). We also used International Classification of Diseases, 9th Revision, Clinical Modification (ICD.9.CM) codes17 for retrieving the type of surgery (13.2 and 13.41 for ECCE and PE surgeries, respectively). Patients younger than 30 years and cataract types other than senile cataracts were excluded.

Sample size was determined using the formula, n = [Z2 × P × (1-P)/d2)], where d = 0.05, type I error of 0.05 and estimating that at least 30% were SECS; based on a previous pilot assessment, the sample size was calculated to be at least 325 annually. For comparing the trends, we chose 15% of senile cataract procedures per year, which would be sufficient according to the calculated sample size. If the selected patient had a history of senile cataract surgery in the fellow eye, the procedure was considered SECS, unless it was registered as the first-eye surgery. We assessed the output of the operating room in terms of the proportions of first- and second-eye operations in each year.

When there were no other cataract surgery codes in the patient’s computer-based records, paper records extracted from the hospital’s medical records department and the patient’s past surgical and medical history were checked to find out whether they had already had any other cataract surgery in the fellow eye.

Statistical analysis was performed using SPSS-17, and the proportion of annual SECS and the 95% confidence interval (CI) were considered the main outcome measurements. For patients who underwent SECS, the mean and standard deviation of the time interval between the two operations were calculated in months. A logistic regression model was used to indicate the time-trend of SECS and the effects of all measured variables on main outcome.

RESULTS

Of 10,517 senile cataract operations performed from the beginning of 2006 to the end of 2009 in this medical center, 1585 were selected. Of these, 1139 (71.9%; 95% CI, 69.5-74.1) and 446 (28.1%; 95% CI, 25.9-30.35) were first- and second-eye operations, respectively. The mean ages of patients who underwent first and second operations were 67.46 ± 11.31 and 67.84 ± 11.63 years, respectively (P = 0.55). Overall, the predominant surgery type was PE (1411/1585, 89%), which increased from 84% in 2006 to 93.7% in 2009 (P < 0.001).

Table 1 shows the patients’ demographic characteristics, SECS rates, and the time interval between the two procedures. Most of the patients were aged between 50 and 80 years (82.3%), underwent PE as their first-eye surgery (90.7%), and had complete insurance (82.8%). The proportions of men and women were almost equal. Overall, the median (interquartile range) time interval between the first and second cataract operations in patients who underwent SECS was 9 (4-24) months.

Table 1

The proportion of second-eye cataract surgery by patients demographic characteristics (2006-2009)

Neither the SECS rates nor the intervals between procedures were significantly different in different age groups, the two sexes, or people with different types of insurance coverage. On the contrary, the SECS rate rose significantly during the 4 years of the study (P = 0.017) and both the SECS rate (P = 0.016) and the time interval (P = 0.02) had a significant relationship with the type of first cataract surgery; the SECS rate was higher (29.9% vs. 19.5%) and the time interval (8 vs. 21 months) was shorter in patients who had undergone PE as their first surgery.

There was a linear increasing trend for SECS throughout the study period (beta = 0.031; P = 0.003); thus, the SECS rate increased an average of 3.13% (95% CI, 3.08-3.19) each year. A consistent increasing trend was also seen in different age subgroups [Figure 1], but it was greater in people over 80.

Figure 1

Time-trends for second-eye cataract surgery rates in different age groups (2006-2009)

The logistic regression test was used to assess the adjusted and non-adjusted odds ratios (OR) of different variables on the SECS rate [Table 2]. Different age groups, sexes, and groups with different insurance types did not differ in their rates of SECS in the adjusted or non-adjusted analyses. The SECS rate increased during the study period (adjusted OR, 1.15; 95% CI, 1.03-1.27; P = 0.01) and was more common in the patients who underwent PE as their first-eye cataract surgery than those who had ECCE (OR, 1.57; 95% CI, 1.03-2.42; P = 0.038).

Table 2

Relationships between second eye cataract surgery proportion and patients characteristics in a logistic regression model

DISCUSSION

In our study, the number of senile cataract operations increased from 1978 in 2006 to 3094 in 2009. The proportion of SECS was 28.1% which increased from 24.3% to 33.4% over this period. Increases in cataract surgery have been reported from nearly all over the world. In Sweden, from 1992 to 2000, the cataract surgery rate increased 54.8%, contributed mainly by SECS, and the proportion of SECS was 36.8% in 2000.2 In Spain, the ratio of SECS increased from 24.8% in 2000 to 31.8% in 2002.3 In the USA, the cataract surgery rate increased by 14% annually between 1980 and 2004, and over 10 years the proportion of SECS increased from 25% to 34% of all cataract surgeries.4 A large computer database analysis in the United Kingdom showed that 65% of patients in 1997 were admitted for surgery to their first eye, and the remainder for second-eye cataract extractions.5

Patients are more satisfied after SECS in comparison to the first cataract surgery.8 There is a greater need for SECS in patients with more active personal, occupational, and social life who need binocular vision.1018 In addition, SECS has been introduced as an extremely cost-effective procedure and has a unique effect on quality-adjusted life years. Nevertheless, according to a previous study in our country,15 the cataract surgery rate is much less than the rates in the developed countries.2419 According to the Vision 2020–the right to sight goal, to eliminate avoidable blinding cataract in developing countries, the coverage of cataract surgery should be improved. However, due to shortage of facilities, achieving a high rate of SECS could leave bilateral cataract the most treatable cause of blindness in developing countries. A recent rapid assessment of avoidable blindness (RAAB) survey in Iran14 showed that “unawareness of treatment” is the main barrier to cataract surgery and accounts for 44% of the reasons in patients with unilateral and bilateral blindness or severe visual impairment. The other important barriers were unreasonable “waiting for the maturity of cataract” (11.4%) and “fellow eye still OK!” (11.4%). These reasons were not significantly different among men and women. The cost of the procedure was not a major barrier in Iran because all insurance services cover cataract surgery costs and this surgery is almost free for patients in many cases.14

The overall median interval between first and second cataract operations in patients who underwent SECS was 9 months which was nearly stable during the study period. In Sweden, in a group of patients with bilateral cataract who were categorized as a delayed SECS group, the average time interval between the two procedures was 5.5 months20 In Spain,3 the mean interval was 7.5 months. It seems that the interval between the two operations is considerably higher in our setting than reported in previous studies. A short interval between the first and second operation is associated with lower costs, especially in younger patients who survive longer after surgery.20

Although SECS increased in all age groups over time, this pattern was more predominant in patients over 80 years and may be explained by probably greater access of older patients to medical care and/or to population aging. In Spain3 and Sweden,2 60.9% and 66% of SECS, respectively, was performed on women. In our study, this rate was 48% and consistent with the rate of cataract surgery in developing countries.13

In some studies,23 like the current study, the mean age was not much higher in patients who underwent SECS than for the first surgery. However, Castells et al.18 reported, after adjustment for visual acuity, a threefold SECS rate in younger patients who were more socially active than those aged over 74 years. Castells et al.,7 in a prospective study with 2 years’ follow-up of patients scheduled for first cataract surgery, reported a threefold higher probability of SECS among younger patients than those aged over 75 years. Javitt et al.6 showed that different age groups experience a similar improvement after SECS.

On the contrary to other developing countries,1 PE constituted the major proportion of surgeries in our study (89%). There is a global rising trend for PE,24 which gives better visual outcomes.1 In our patients who had undergone PE as their first surgery, the SECS rate was 6% higher and the interval between operations was nearly 13 months shorter than for ECCE. Therefore, it seems that these patients were more likely to have SECS. Since patients return for post-operative follow-up at different times, which led to some missing data, and inconsistencies existed in patient records (uncorrected or best corrected visual acuity [UCVA, BCVA] or both were recorded on different days), the post-operative visual acuities are not included in this report. However, it seems that post-operative VA influences the patient’s decision for the SECS. Hence, we recommend inclusion of visual acuity in future studies.

Our study was performed in a major referral eye hospital, where 10,517 senile cataract surgery procedures were performed during the study period. The number of cataract operations in this academic and referral hospital increased 1.5 fold over the study period. The proportions of second-eye operations also rose from 1/4 to 1/3 during the same period of time with an annual increase of 3.13%, independent of patient demographics. This is the first study to show the SECS rate in a representative sample of tertiary eye care providers in Iran. Most patients who come to this center have full insurance and belong to low and middle socioeconomic levels.21 These figures to some extent explain the growing cataract surgical services in tertiary eye care hospitals in our country. However, the results could not be generalized at a national level.