In one of the largest prospectively recruited studies of primary RRD, we found the annual incidence in a population of 5.1 million to be 12.05 per 100,000 population. In the United Kingdom, this rate equates to approximately 7300 incident cases of primary RRD annually.
There have been several studies over the past 40 years that were conducted with the principal goal of estimating the incidence of primary RRD, reporting a wide range of results.
4–16 In only one study, from Beijing, China,
17 was a population comparable to ours in size examined, and it produced a much lower estimate of annual incidence (7.98 per 100,000; 95% CI, 7.3–8.67). This difference may be attributable in part to the age distribution of the study population. In Beijing, 14% of the population was older than 60 years, compared with 22.6% in Scotland. In previous reports with a sample size of more than 500 cases, a minimum recruitment period of 1 year, and predefined case eligibility, the annual incidence varied nearly twofold, between 7.98 and 14 per 100,000.
4–6,17 In reports from European countries only, a similar variation exists, with annual incidence rates varying between 6.9 and 14 per 100,000 population.
6,10 There are several possible reasons for the noted variation: the methodology used in previous studies has differed considerably
18 ; there were no clearly defined inclusion criteria across studies making accurate comparison problematic. RRD incidence varies with age, sex, affluence and prevalence of both myopia and pseudophakia; thus, characteristics of the underlying study population will influence the reported incidence. Finally, changing treatment modalities for RRD and a move toward more daycase surgery and outpatient procedures
19 may influence case recording, making comparison of rates between countries and different time periods difficult.
We found a large difference in the incidence of RRD between men and women (M-F ratio, 1.68:1). The significant difference in incidence persisted in the age-standardized incidence ratios (M-F, 1.76:1) and was not affected by excluding trauma and previous cataract surgery (M-F, 1.40:1). Within the pseudophakic group, the overrepresentation of men was even more marked (M-F, 2.3:1), despite a higher rate of cataract surgery in women in the United Kingdom.
20 Most previous studies show a higher incidence in males,
8,11,13,14,21 (M-F, 1.3:1 to 2.3:1); a minority have found that women predominate in the phakic, nontraumatic group.(M-F, 1:1.16 to 1:1.4)
5,12 A meta-estimate of previous studies reporting the sex distribution in RRD incidence indicate a male proportionality of between 52% and 59% (
P < 0.0001; Supplementary Fig. S2). Long-term cohort studies in Taiwan have demonstrated that the risk of RRD after cataract surgery is higher in males. The increased risk of RRD in patients with myopia and a history of RRD was seen to be significant in males only, up to 4 years after cataract surgery.
22,23 Perhaps, due to lifestyle differences, the men tend to underreport lesser trauma that may contribute to RRD risk; however, there may also be an inherent difference in sex risk. The age distribution of our cases indicates a peak in both sexes in the 60- to 69-year age group, widely supported by the findings in other studies.
4–16
The right eye was involved more frequently than the left eye (1.26:1); most studies support this finding (ratios ranging between 1.09:1 and 1.36:1).
5,7,9,10,17 Excluding all cases with previous cataract surgery and reported trauma, we continued to find a right-to-left eye ratio of 1.18:1 (
P = 0.001). A meta-estimate of previous studies reporting this statistic indicates a right eye proportionality of 53.5% to 56.7% (
P < 0.0001; Supplementary Fig. S2). The reason for the greater incidence in the right eye remains unknown.
Socioeconomic status can affect the incidence of many diseases and the association between deprivation and visual impairment is well known.
24 Unexpectedly, we found a disparity in the incidence of RRD between socioeconomic groups, with an association between affluence and RRD. This trend was a significant finding in both sexes but was much more marked in men. The trend was significant in five of seven socioeconomic demographic domains that determine the overall deprivation score and the strongest association was found in the domain of educational achievement (χ
2 trend = 40.21;
P = 2.3 × 10
−10). In addition to the association with affluence, the characteristics of RRD at presentation showed dramatic variation between quintiles of deprivation. RRD cases from the most deprived quintile more frequently presented with a total RRD (13% vs. 4%) and more frequently presented when the macula was detached (65% vs. 51%) when compared with the least-deprived quintile. These findings indicate that cases from more deprived areas tend to present later and with more extensive detachments. This trend has important consequences for final visual prognosis.
We explored several possible explanations for the association between RRD and affluence. The incidence of RRD increases with age to a peak in the sixth decade. Age-specific mortality rates may differ between the most deprived and least deprived quintiles so that fewer people from deprived areas live long enough to be at greatest risk of retinal detachment. Similarly, elderly individuals may have accrued more wealth over many years and a larger proportion of elderly individuals may live in affluent areas. However, we found a significant increase in the age-specific incidence of RRD across quintiles of deprivation in the age groups comprising the highest natural incidence of RRD (age groups, 50–59 and 60–69), suggesting that the influence of age was not the primary factor behind the association with affluence (Supplementary Table S5).
Trauma may influence the incidence of RRD; however, the proportion of traumatic cases was equal across quintiles. Previous cataract surgery, a known risk factor for RRD, did not significantly influence the association with affluence, as more pseudophakic RRD cases were present in the more deprived quintiles.
This study has only recorded patients on presentation to hospital, and it is possible that patients from areas of greater deprivation have poorer access to health care services and have been excluded from the study. However, based on the SIMD classification of our cases, those from the most deprived areas ranked higher than those from the least deprived areas in the geographic-access-to-services domain, which suggests that access to essential services was not a limiting factor in presentation to a hospital.
Myopia is a significant risk factor for RRD and has been associated with higher educational achievement and IQ, and thus, perhaps, higher income and socioeconomic status.
25–27 It is interesting to note that of the SIMD rank determinants, the strongest association was found between RRD and educational achievement. Detachments in the most affluent quintiles were more likely to be associated with myopia than those in the most deprived quintiles. This increased proportion of myopic RRD cases in more affluent areas is an important factor that partly explains the increase in RRD incidence between the most and least deprived quintiles. Although myopia is an important factor in the observed association between RRD and affluence, we cannot exclude other, as yet unidentified risk factors associated with socioeconomic status that may underlie this observation.
In summary, we prospectively estimated the overall incidence of primary RRD in Scotland to be 12.05 per 100,000 population. Men were affected more than women in all age groups and all types of RRD. More than 50% of all phakic cases were myopic. One in five cases with RRD had had cataract surgery. RRD incidence and the proportion of myopic RRD are significantly associated with affluence; however, RRD cases from more deprived datazones frequently present with a more extensive area of detachment.