Click on the links below to access all the ArticlePlus for this article.
Please note that ArticlePlus files may launch a viewer application outside of your web browser.
Retinal detachment is a serious condition that can lead to blindness. Risk is increased among people who are myopic (nearsighted). The identification of risk factors and predisposing lesions for retinal detachment is important both for primary prevention and for management of myopia. Valsalva hemorrhagic retinopathy1 is a less severe condition characterized by generally self-resolving vision disturbances due to rupture of retinal capillaries following the Valsalva maneuver (forced holding of breath against a closed glottis). We considered the possibility that heavy lifting activities requiring the Valsalva maneuver2–4 could be a risk factor for retinal detachment. Searches of PubMed and Embase revealed a single physiologic study addressing this question.5 In healthy subjects, lifting weights over 15 kg triggered an intraocular pressure spike (∼25 mm Hg), particularly when accompanied by the Valsalva maneuver. The authors of the study suggested that these hemodynamic spikes might trigger retinal detachment.5 In a reported case series on retinal detachment, most patients had performed heavy physical activities.6 However, there are no analytic studies on associations between lifting and retinal detachment. We performed a case-control study to investigate the hypothesis that repeated lifting tasks could be a risk factor for retinal detachment among people already at high risk because of myopia.
Study Design and Participants
Cases were people with surgically treated retinal detachment accompanied by any degree of myopia. We initially screened all patients who had received surgical treatment for retinal detachment at the Department of Ophthalmology, Ospedale Maggiore, Bologna, between October 2000 and December 2001. Questionnaires were mailed to all 109 of these patients resident in the main catchment area. Written replies were received from 94 (86%). Between January and March 2002, an additional 26 patients were contacted during their hospital visit and given the questionnaire providing a total of 120 persons with retinal detachment (overall response rate, 89%). We then restricted our cases to the 61 respondents who also had myopia according to clinical records.
For the control group, we screened all 99 subjects with myopia (of any degree) who underwent outpatient examination on weekdays in January to September 2002 at 3 public ophthalmologic surgeries located within the hospital's catchment area (west Bologna). All 99 subjects agreed to fill in the same questionnaire. All study participants provided informed consent for anonymous data publication. In Italy, formal application for ethical approval was not possible for observational research at the time of the study (internal approval was granted).
Participants were aware that the research related to retinal detachment, but they were unaware of the study hypothesis. The questionnaire included detailed questions on past and current jobs that required regular lifting of >10 kg (see Appendix, available with the online version of this article). The information on lifting was checked for plausibility by an experienced ergonomist (R.B.) who was unaware of the case-control status; no discrepancy was found.
We used Stata 9.0 (StataCorp, College Station, TX). We applied skewness-kurtosis tests to assess normal distributions. For non-normal distributions, we conducted 2-sample (Wilcoxon rank-sum) tests. To quantify exposure, we devised a “cumulative lifting index,” calculated as the product of load (kg), frequency (number of lifting maneuvers/wk), and number of years of lifting. Subjects who reported “no lifting” were considered the reference category; the median was used as a cut-off to distinguish “light” and “heavy” lifting. We classified body mass index BMI according to quartiles among controls,7 taking the 2nd quartile as the reference category. Myopia was categorized by severity in diopters, expressed as spheres (−0.5 to −5.75; −6 to −9.75; −10 or worse). Variables that reached P < 0.1 at univariate analysis were entered in an unconditional logistic regression model, additionally adjusted for age and sex (educational level was not entered due to collinearity). We estimated odds ratios (ORs) and 95% confidence intervals (CIs) according to Breslow and Day.8
The 61 cases comprised 26 women and 35 men (reflecting an expected male predominance)9,10; the 99 controls included 49 women and 50 men. Mean (SD) age was 56 (18) years for cases and 55 (15) years for controls. The degree of myopia was −5.5 (4.7) diopters for cases and −4.5 (2.5) diopters for controls. Mean BMI was higher in cases (25.4 [3.8] vs. 23.5 [3.1] kg/m2). Lifetime prevalence of manual lifting work was 57% (35/61) among cases and 32% (32/99) among controls.
Table 1 reports univariate and multivariate analyses. Consistent with the literature,9–18 we found strong associations with eye operations (62% of which had been performed for cataracts), for injuries to the eye or head, and for severe myopia. A strong association was also recorded for high BMI (OR = 6.8; 95% CI = 1.6–29). Subjects reporting the heaviest cumulative lifting showed a 4-fold increased risk compared with those who reported no manual lifting (4.4; 1.5–13). Likelihood ratio tests did not detect interactions between BMI and lifting, BMI and eye surgery, or lifting and eye surgery (not shown).
This case-control study suggests that myopic subjects who frequently perform heavy manual lifting may have an increased risk of retinal detachment as compared with other myopic subjects. The risk of retinal detachment also appeared to rise with BMI. We focused on myopic subjects because of the potential preventive implications in this subset of persons who are already at increased risk9,10,16–18 for retinal detachment. Furthermore, myopic subjects may be especially sensitive to risk factors that also affect nonmyopic people, thus offering clues about the etiology of retinal detachment more generally. In multivariate analysis, heavy manual lifting remained a strong risk factor even after taking into account the contributions of known risk factors such as severe myopia, history of eye surgery and eye/head trauma.11,12,16,19 Physiopathologically, various factors related to Valsalva maneuvers might help explain this association (including vitreal traction, raised pressure in the choroid, and possibly even recurrent Valsalva hemorrhagic retinopathy).
We found no evidence of an association with lighter occupational lifting, although our study lacked power to detect small effects. In a condition such as lumbar disk herniation, in which lifting is a prominent risk factor, various aspects of exertion (intensity, frequency, and long-term history) are thought to contribute separately to risk.20 Future studies could explore the possible separate roles of these aspects of lifting to the risk of retinal detachment.
High BMI (≥25.5 kg/m2) also appeared to be strongly associated with risk of retinal detachment among people with myopia. This unanticipated finding might be related to known associations between high BMI and risk factors for vascular damage such as hypertension, diabetes, and hyperlipidemia, which in turn may affect the retinal capillaries. Some studies have reported associations between increased intraocular pressure and vascular risk factors, including high BMI,21–23 although hospital-based studies17,24 have not produced similar results. The excess risk associated with elevated BMI might also be at least partially explained in biomechanical terms. An overweight person will have to lift a greater total load (including trunk and arm weight) than a normal-weight subject to perform the same external lifting operation, presumably leading to more intense Valsalva maneuvers. This finding deserves to be explored in more detail.
This small study did not permit stratified analysis and was also vulnerable to biases inherent to nonpopulation-based case-control studies. Differential severity of underlying eye conditions between the cases (hospital outpatients) and controls (outpatients from a local public health service eye clinic) is also possible. Furthermore, the choice of setting for the control group may have led to systematic differences in comparison with people in the general population who have myopia, especially in terms of concomitant eye conditions. Such considerations might conceivably have led to underestimates in the risks associated with lifting, because blue-collar workers tend to have more concomitant pathologies than white-collar workers.25 Geographically, the catchment areas of the hospital and public surgeries almost coincided (so a control who developed retinal detachment would likely have become a case); in a supplementary analysis (not shown) matched for residence, age, and sex, the results remained substantially unchanged, although with wider confidence intervals. Socioeconomic selection may not be a major concern because private-sector patients would likely belong to professional classes unexposed to heavy occupational lifting (and myopic patients of private surgeries would tend to be referred to private hospitals).
In conclusion, this study provides preliminary evidence supporting the physiopathologically plausible hypothesis that heavy occupational lifting is a risk factor for retinal detachment in people with myopia. We think that larger studies of people with and without myopia in the general population are warranted. The possibility that the risk of retinal detachment could be increased in the presence of obesity also deserves consideration.
We thank Carmen Giacomini and Giorgio Valdè, the physicians who first pointed out and illustrated to us the concerns that many ophthalmologists have about patients’ undertaking lifting maneuvers after surgical treatment of retinal detachment.
1. Duane TD. Valsalva hemorrhagic retinopathy. Trans Am Ophthalmol Soc
. 1972;70:298 –313.
2. MacDougall JD, McKelvie RS, Moroz DE, et al. Factors affecting blood pressure during heavy weight lifting and static contractions. J Appl Physiol
3. Rafuse PE, Mills DW, Hooper PL, et al. Effects of Valsalva’s manoeuvre on intraocular pressure. Can J Ophthalmol
4. Dickerman RD, Smith GH, Langham-Roof L, et al. Intra-ocular pressure changes during maximal isometric contraction: does this reflect intra-cranial pressure or retinal venous pressure? Neurol Res
5. Pivovarov NN, Malakhova LA, Bagdasarova TA, et al. Role of weight lifting in the development of retinal detachment. Vestn Oftalmol
. 1977; 6:50 –53.
6. Synek S, Vlkova E. Work capacity evaluation in patients after surgery for detached retina. Cesk Oftalmol
7. Miettinen OS, Cooke EF. Confounding: essence and detection. Am J Epidemiol
8. Breslow NE, Day NE. Statistical Methods in Cancer Research.
Vol 1. Lyon: International Agency for Research on Cancer; 1980.
9. Haimann MH, Burton TC, Brown CK. Epidemiology of retinal detachment. Arch Ophthalmol
. 1982;100:289 –292.
10. Sasaki K, Ideta H, Yonemoto J, et al. Epidemiologic characteristics of rhegmatogenous retinal detachment in Kumamoto, Japan. Graefes Arch Clin Exp Ophthalmol
11. Tielsch JM, Legro MW, Cassard SD, et al. Risk factors for retinal detachment after cataract surgery. A population-based case-control study. Ophthalmology
12. Norregaard JC, Thoning H, Andersen TF, et al. Risk of retinal detachment following cataract extraction: results from the International Cataract Surgery Outcomes Study. Br J Ophthalmol
13. Williams DF, Mieler WF, Williams GA. Posterior segment manifestations of ocular trauma. Retina
14. Goffstein R, Burton TC. Differentiating traumatic from nontraumatic retinal detachment. Ophthalmology
15. Wyszynski RE, Grossniklaus HE, Frank KE. Indirect choroidal rupture secondary to blunt ocular trauma. A review of eight eyes. Retina
16. Ducasse A, Segal A, Jouhaud F, et al. Retinal detachments. Etiological and epidemiological aspects. Bull Soc Ophtalmol Fr
17. Austin KL, Palmer JR, Seddon JM, et al. Case-control study of idiopathic retinal detachment. Int J Epidemiol
18. Törnquist R, Stenkula S, Tornquist P. Retinal detachment. A study of a population-based patient material in Sweden 1971–1981. Acta Ophthalmol
19. Rowe JA, Erie JC, Baratz KH, et al. Retinal detachment in Olmsted County, Minnesota, 1976 through 1995. Ophthalmology
. 1999;106: 154 –159.
20. Bernard BP. Musculoskeletal Disorders and Workplace Factors. A Critical Review of Epidemiologic Evidence for Work-Related Musculoskeletal Disorders of the Neck, Upper Extremity, and Low Back.
US. Department of Health and Human Services, Public Health Service: Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health; July 1997.
21. Bec P, Arne JL, Mathis A, et al. Possible vascular factor in idiopathic detachment of the retina. J Fr Ophtalmol
22. Zinn KM, Field R, Schepens CL. Role of cardiovascular disease in the pathogenesis of rhegmatogenous retinal detachments. Trans Ophthalmol Soc U K
. 1978;98:134 –141.
23. Mori K, Ando F, Nomura H, et al. Relationship between intraocular pressure and obesity in Japan. Int J Epidemiol
24. The Eye Disease Case-Control Study Group: risk factors for idiopathic rhegmatogenous retinal detachment. Am J Epidemiol.
1993; 137:749 –757.
25. Peate WF. Work-related eye injuries and illnesses. Am Fam Physician