Purpose To estimate the incidence and clinical characteristics of rhegmatogenous retinal detachment (RRD) in Taiwan.
Methods This was a nationwide, population-based retrospective study of patients with RRD. Data from the Taiwan National Health Insurance Research Database (2000–2012), which represents 4% of the total population in Taiwan, were analysed. The incidence of RRD and its associations with age, gender and high myopia were analysed.
Results A total of 2359 patients with RRD (1336 men and 1023 women) were identified from 2000–2012. The age-standardised incidence rate of RRD over the 13-year period was 16.40±1.06 per 105 person-years (18.89 and 13.93 for men and women, respectively, p<0.0001) and an average age of 47.76±0.67 years. The incidence in both genders had an obvious peak at 50–69 years of age, and a secondary peak at 20–29 years in women. Concomitant high myopia was noted in 10.51% of the patients, with an average of 39.72±1.95 years. Prior cataract extraction was noted in 11.06% of the patients, including 17.64% in the patients RRD aged ≥50 years and 4.04% in those younger than 50 years. The average age of the patients with pseudophakic or aphakic RRD was 61.85±1.60 years.
Conclusions The annual incidence of RRD in Taiwan is comparable to most Western countries, with a relatively younger mean age. The male patients were more susceptible to retinal detachment in almost all age groups. Retinal detachment in patients with high myopia was associated with a younger age at onset.
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Rhegmatogenous retinal detachment (RRD) is a major cause of visual loss. Risk factors for RRD include male gender,1 a history of trauma,2 congenital anomalies,3 cataract extraction4 and myopia.3 ,5 ,6 Myopia is highly prevalent in the Chinese,7 ,8 and most residents in Taiwan are Chinese in ethnicity. According to a nationwide survey in Taiwan in 2000,7 the prevalence rate of myopia was 84% for schoolchildren aged 16–18 years, with mean refractive indices of −4.12 D in girls and −3.15 D in boys at 18 years of age. In addition, the survey also reported high myopia (>−6.0 D) in 24% of girls and 18% of boys at 18 years of age. Since myopia is a risk factor for RRD, the annual incidence of RRD may be higher in Taiwan. The purpose of this study was to investigate the annual incidence and clinical characteristics of RRD in Taiwan using a population-based study design with data from the Taiwan National Health Insurance (TNHI) Research Database.
Materials and methods
Longitudinal data over a 13-year period were obtained from the TNHI Research Database and analysed. The TNHI programme was initiated in Taiwan in 1995 and includes the medical records of more than 95% of the hospitals and clinics in Taiwan that are contracted with the TNHI Bureau. More than 98% of the Taiwanese population has been covered by the TNHI programme since 2001. Clinics and hospitals have to register all treatments to apply for financial reimbursement; thus, the accuracy of the database is considered to be reliable. The National Health Research Institute (NHRI) created a data set of one million randomly selected residents of Taiwan who were enrolled in the TNHI programme in 2005 for research purposes, and their healthcare records were analysed in this study. This sample comprises almost 4% of the population in Taiwan and was resampled by the NHRI to confirm its structural resemblance to the general population with respect to gender and age, thus this data set has been validated as representing the entire population of Taiwan. This study was approved by the Institutional Review Board of Changhua Christian Hospital and the procedures conformed to the tenets of the Declaration of Helsinki.
Patients with at least two clinical visits with a diagnosis of RRD (International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code: 361.0) from January 2000 to December 2012 who underwent retinal detachment repair by pars plana vitrectomy, scleral buckling or pneumatic retinopexy were recruited in this study. Patients with a previous history of open globe injury (ICD-9-CM: 871), proliferative diabetic retinopathy (ICD-9-CM: 362.02) or tractional retinal detachment (ICD-9-CM: 361.81) were excluded. Each patient was counted only once even if they underwent further operations to repair retinal detachment. Patients with bilateral retinal detachment were also only counted once.
The yearly age-standardised incidence rate (ASIR) from 2000 to 2012 was calculated as the incidence rate standardised according to age distribution based on the world standard population in 2000 according to WHO. On the other hand, the age-specific incidences were calculated by stratifying on age and gender. For each incidence rate, a 95% CI was calculated. We analysed the demographic and clinic factors among the patients with RRD by using a two-sample t test to compare the mean age, proportions of myopia and previous history of cataract surgery between genders. A p value <0.05 is considered statistically significant.
A total of 2359 patients with RRD (1336 men and 1023 women) were included in this study (table 1). The ASIRs of RRD were fairly stable over the 13-year study period (figure 1). The average ASIR was 16.40 (95% CI 15.34 to 17.46) per 105 person-years, including 18.89 (95% CI 17.39 to 20.39) for men, which was nearly 1.35-fold higher than that for the women (13.93; 95% CI 12.74 to 15.13), and the difference was statistically significant (p<0.0001) (table 1). The overall median age was 50 years (50 years for the men and 50 years for the women), and the average age was 47.76 years (95% CI 47.09 to 48.42), with no significant difference between the men and women (48.11 years vs 47.30 years). Figure 2 shows the age-specific incidence for each age group. There was a major peak at 50–69 years of age (>41 per 105 person-years) in both genders, and also a smaller peak at 20–29 years of age in the female patients (15.63 per 105 person-years). The overall male-to-female ratio was 1.31:1, with a higher incidence in the men at all age groups except for 20–39 years, at which the incidences were similar (13.43 to 15.63 per 105 person-years) in the men and women (table 1).
RRD with high myopia
Among the 1336 men and 1023 women with RRD, 248 (10.51%) were diagnosed with high myopia, including 127 men and 121 women. There was no statistically significant difference in the ratio of high myopia between genders (p=0.71). Figure 3 shows the distribution of age in the patients with RRD with high myopia. The median and average ages of these patients were 39 years and 39.72 years, respectively, (95% CI 37.73 to 41.59), which were about 8 years younger than those of the whole group. The proportion and number of patients with high myopia peaked at an age of 20–29 years (table 2); however, there were different peaks of patient numbers in age between the men and women (50–59 years and 20–29 years, respectively). In addition, there were more female than male patients with RRD with high myopia in the 20–29 years age group and in the senile group (≥60 years), and far more male than female patients with RRD with high myopia in the 50–59 years age group (table 2).
Previous cataract extraction
Among the 1336 men and 1023 women with RRD, 261 (11.06%) (158 men and 103 women) had a previous history of cataract surgery. Although male patients outnumbered female patients, there was no statistically significant difference in the ratio of pseudophakic or aphakic RRD between the male and female patients (p=0.58). Figure 4 shows the distribution of age at a diagnosis of RRD in the patients with a history of cataract surgery. The median age was 63 years and the average age was 61.85 years (95% CI 60.25 to 63.45), with no significant difference between men and women. Of the patients older than 50 years, 17.64% had a history of cataract surgery, whereas among those younger than 50 years, only 4.04% had undergone cataract surgery before RRD.
The population-based incidence of retinal detachment has been reported in many areas,9–13 ranging from 7.98 to 18.2 per 105 person-years. The annual incidence of RRD in our study is similar to that recently reported in Western countries (18.2 per 105 person-years in the Netherlands and 17.9 per 105 person-years in Olmsted),9 ,10 but higher than the incidence reported in ethnic Chinese in Singapore (11.6 per 105 person-years) and in Beijing (7.98 per 105 person-years).11 ,12 Differences in age distribution and the method of data collection may explain the different incidence rates among the three studies including ethnic Chinese populations. Since our results were based on data from the TNHI Bureau, in which every treatment has to be claimed for reimbursement, and since there is excellent accessibility to a qualified ophthalmologist for proper care and modern management for RRD throughout Taiwan, the likelihood of underestimating the incidence of RRD should be minimal and the incidence of RRD should be highly reliable in this study.
The median (50 years) and mean (47.76±0.67 years) ages in the present study are younger than reports from Western countries,9 ,10 ,13 but similar or older than reports including other Chinese populations.11 ,14 Differences in the mean age of patients with RRD between different ethnic groups was also reported by Chandra et al,15 who reported that patients from South Asia had a younger age at onset and more myopic refraction than patients in Europe. Generally speaking, an increased incidence of RRD was noted along with increasing age until 70 years in this study, which is in line with other reports.9–13 However, the incidence of RRD in the younger age group (below 39 years) in this study (table 3) was much higher than in reports from Western countries.5 ,6 ,8 ,10 ,13 Besides, we noted bimodal age peaks of RRD in our study, which has also been reported in previous studies on Chinese patients.12 ,14 As high myopia is an important risk factor for RRD in younger patients,14 the higher incidence of RRD in the young patients in this study may be due to the high prevalence of myopia in these patients in Taiwan.7
In this study, a higher incidence of RRD was found in the male patients in almost every age group (table 1), which is consistent with most previous studies.11–15 Trauma has been reported to be associated with an increased incidence of RRD in men.1 ,2 Cataract extraction, another major risk factor for RRD, may also be responsible for the male predominance, as previous reports have shown that male gender is a risk factor for pseudophakic RRD in Taiwan.16 Our results also demonstrated a higher number of pseudophakic RRD in the male patients, with a male to female ratio of 1.53 to 1, which although not statistically significant, may contribute to the higher incidence in men overall. Long axial length, a well known risk factor for RRD after cataract extraction,17 ,18 may be another reason for the higher incidence of RRD in the male patients. Previous reports have shown that the average axial length is longer in men, in school children (0.4 mm average difference)19 and in the elderly (0.56 to 0.57 mm average difference).20 ,21
The exception for male predominance was in the 20–39 years age group, in which the incidence of RRD was approximately equal in the men and women (figure 2). Similar incidence rates of RRD between genders at this age interval have also been reported in studies from other areas (table 3).10 The higher number of RRD with high myopia in female patients from age 20 years to 39 years in this study may have contributed to the similar incidence of RRD in this age group.
Previous cataract extraction
Cataract extraction is generally considered to be a major risk factor for RRD in the elderly.9 ,10 The median age of pseudophakic or aphakic RRD (63 years) in this study is similar to a previous study.10 However, in our study, the rate of previous cataract extraction was 11.06% for all cases, which is lower than in reports from Western countries (ranging from 19% to 33.5%).11–13 Since cataract extraction has become popular in the past 20 years in Taiwan, and the fact that the cost of surgery is covered by the national insurance programme, delayed surgery for a cataract is not likely to be the reason for the lower rate of pseudophakic or aphakic RRD in Taiwan. The higher proportion of younger age patients in this study, most of whom were not old enough to develop a cataract, may be the reason for the lower rate of pseudophakic RRD.
In this study, high myopia with RRD was noted in 10.51% of the patients with a much younger average age. The number of high myopia in the patients with RRD also varied with age, being highest at 20–30 years and then declining with age (figure 3). Previous studies have shown that myopia is a major risk factor for RRD in young adults.3 ,13 ,14 ,22 ,23 Chou et al14 had shown in their study that the average refractive status for patients with RRD aged between 20 years and 29 years in Taiwan was about −8.0 D, and in this group of patients, the major type of retinal breaks were holes, or lattice degeneration with holes, in contrast to patients aged over 50 years, who were average moderate or low myopic and more often had flap tears. This may reveal the facts that in Taiwan, eyes with high myopia tend to have RRD develop at a younger age and have different clinical pictures. In this study, we noted that in both genders, proportion of patients with RRD with high myopia peaked at the age between 20 years and 29 years (table 2). However, the incidence of high myopia is higher in women among the general young population in Taiwan (men: 18%, women: 24%),7 this may explain the higher number of RRD with high myopia in women at the age interval between 20 years and 29 years (male to female ratio: 0.79). Though the number of patients with high myopia with RRD in male patients was highest from 50 years to 59 years, the proportion of high myopia at this interval in men is far less than that in the younger ages (table 2). Another interesting finding in this study is that in patients over 60 years, the proportion and the patient number of high myopia in women are far above that of men. This could be explained by the fact that macular hole associated RRD, which comprised 5% of non-traumatic phakic RRD in Taiwan14 is mostly observed in senile, myopic, female patients.24
The main limitation of this study is that the diagnostic code of high myopia may not have been documented always, since myopia is highly prevalent in Taiwan and the diagnosis of myopia is frequently missed, and thus the rate of patients with RRD and high myopia may have been underestimated. However, the results did show a trend that high myopia is an important risk factor for RRD in younger patients. Another limitation of this study is that the type of breaks responsible for RRD could not be traced in the NHRI data set. According to previous studies on RRD in Taiwan,14 atrophic holes with or without degeneration are more often responsible for RRD in young patients, whereas flap tears are the major type of breaks for RRD in older patients (about 40 years).
In conclusion, the incidence of RRD in Taiwan is similar to previous reports in other areas. Male predominance and a higher incidence of RRD in the older patients (50–69 years) were also noted. The major difference is that the incidence of RRD was much higher in the younger patients (0–39 years). This will have a socioeconomic impact, since patients in this age group are more socially and economically active. A higher incidence of myopia among the young adult population in Taiwan may be the reason for the increased incidence in RRD among younger patients. A limitation of this study is that it is based on a data set from NHRI, thus the severity and extent of RRD could not be evaluated, and coexisting myopia may not have been registered. However, our results show the distinct clinical characteristics of RRD in ethnic Chinese patients in Taiwan. It is possible that by lowering the incidence and severity of myopia, the incidence of RRD will in turn be lowered.
Collaborators MSS ABBV.
Contributors Conception and design: S-NC and I-BL. Drafting, analysis and interpretation of data: S-NC and Y-JW. Revising it critically for important intellectual content: I-BL and S-NC. Final approval: S-NC.
Competing interests None declared.
Ethics approval Changhua Christian Hospital.
Provenance and peer review Not commissioned; externally peer reviewed.
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