Open Access

Prevalence of cataract in adult Down's syndrome patients aged 28 to 83 years

Clinical Practice and Epidemiology in Mental Health20073:26

https://doi.org/10.1186/1745-0179-3-26

Received: 26 June 2007

Accepted: 22 November 2007

Published: 22 November 2007

Abstract

Background

Age-related cataract is the major cause of blindness in humans throughout the world. The majority of previous studies of cataract in Down's syndrome (which usually results from trisomy 21) have reported that the prevalence of this ocular abnormality is higher for a given age range than in the general population. The objective of the present study was to study the prevalence of cataract in a well-defined population of adults with Down's syndrome.

Methods

An in-patient population of 68 adults (35 males and 33 females) with Down's syndrome, aged between 28.9 and 83.3 years, underwent ophthalmological examination for the presence of cataracts.

Results

Overall, the prevalence of cataract was 16.2%, with no significant difference in the prevalence between males (17.1%) and females (15.2%). In those aged between 45 and 64 years, the prevalence was 16.7%, rising in those aged between 65 and 75 years to 28.6%.

Conclusion

Compared with the general population, the prevalence of cataract in Down's syndrome was raised in those aged 45 to 64, but not in those aged 65 to 75 years; the latter might be a function of the relatively small number of patients in this age group. The increased prevalence of cataract found in those in the 45- to 64-year-old age group may be the result of increased levels of the copper- and zinc-containing superoxide dismutase enzyme (CuZnSOD), in turn resulting from the location of the associated five exons of SOD1 on chromosome 21. These elevated levels of superoxide dismutase may give rise to increased levels of reactive species, including hydrogen peroxide and hydroxyl radicals, which may increase the risk of cataractogenesis. It is suggested that nutritional supplementation with antioxidants may therefore help reduce the prevalence of cataract in Down's syndrome.

Introduction

Age-related cataract is the major cause of blindness in humans throughout the world. In England and the United States the prevalence of cataract in the general population aged 45 to 64 years is between 2 and 8%, rising to between 21 and 39% in the 65 to 75 year age group, and to 65% in those aged 85 years and over [13].

The majority of previous studies of cataract in Down's syndrome have reported that the prevalence of this ocular abnormality is higher for a given age range than in the general population (see Table 1). The present study examined the prevalence of cataract in adult Down's syndrome.
Table 1

Studies of the prevalence of cataract in Down's syndrome

Study

No. of subjects

Age of subjects (years)

Percentage with cataract

Lowe 1949 [11]

67

< 60

87

Skeller & Øster 1951 [12]

80

< 58

46

Cullen & Butler 1963 [13]

143

2–53

15

Chutko 1965 [14]

100

< 18

20

Rochels et al. 1977 [15]

1047

< 23

2

Gnad & Rett 1979 [16]

420

< 14

55

Jaeger 1980 [17]

75

15–68

55

Walsh 1981 [18]

91

5–60

17

Shapiro & France 1985 [19]

53

7–36

13

Riise 1986 [20]

123

< 66

59

Hestnes et al. 1991 [21]

30

21–72

50

Da Cunha & Moreira 1996 [22]

152

< 18

13

Present study

68

28–84

16

Methods

All adults with Down's syndrome in the catchment area of Leavesden Hospital, a large hospital for individuals with learning disability in Hertfordshire, England, were examined in detail clinically and underwent full ophthalmological examination for the presence of cataracts. They included in-patients, day-patients, and those in the community.

Statistical analyses were carried out the SPSS for Windows program (Chicago, USA).

Results

The total number of adults with Down's syndrome was 68, consisting of 35 males and 33 females, ranging in age from 28.9 to 83.3 years (mean 54.1 years, standard deviation (sd) 11.9 years). Eleven individuals were identified as having an ophthalmological diagnosis of cataract, representing a prevalence of 16.2% of the population studied, and there was no significant difference between males (6/35) and females (5/33) (p = 0.82). The mean age of those with a history of cataract was 55.3 (sd 9.0) years compared with 53.8 (sd 12.4) years for those without such a history; this difference was not significant (p = 0.70). The two groups (those with and those without cataract) were also matched for sex (male: female = 6:5 versus 29:28, respectively; χ2 = 0.011; df = 1; p > 0.9).

For those aged between 45 and 64 years, the prevalence was 16.7% (7/42), while for those in the age range 65 to 75 years, the prevalence was 28.6% (2/7).

Discussion

Ocular abnormalities are relatively common in individuals with mental retardation, particularly those with Down's syndrome [4]. In the present study, the prevalence of cataract found in adults with Down's syndrome is consistent with that reported in several previous studies (Table 1). For those aged between 45 and 64 years, the prevalence of cataract in Down's syndrome (16.7%) was significantly greater than that in the general population of England and the United States (2 to 8%). Indeed, Das et al [5] found a prevalence of age-related cataract, aphakia or pseudophakia of zero in a European sample aged between 40 and 49 years, and of 6% (standard error 4.3%) in those aged between 50 and 59 years. For those aged between 65 and 75 years, the prevalence in Down's syndrome (28.6%) was not significantly different from that in the general population (21 to 39%).

Our finding that the prevalence of cataract in those aged between 65 and 75 years did not differ from the prevalence in the general population may be a function of the relatively small number of cases (seven) in our sample in this age group. It is important to consider the possible cause for the impression of an increased rate of cataract in the 45- to 64-year-old age group. The general consensus is that cataracts are usually the result of free radical damage. There is chronic exposure of the ocular surface to oxidative stress, for example from atmospheric oxygen and exposure to ultraviolet light (in sunlight). However, these factors affect Down's syndrome individuals and non-Down's syndrome individuals alike. The question then becomes: is there any evidence that Down's syndrome individuals have greater exposure to free radicals?

Dickinson and Singh have proposed that in Down's syndrome there is increased activity of superoxide dismutase, resulting in overproduction of hydrogen peroxide and hydroxyl free radicals which in turn compromise cellular functioning [6]. Individuals with Down's syndrome typically have trisomy 21; some have only additional portions of chromosome 21, while others show mosaicism [6]. The result is an increased production of many of the proteins encoded by genes on this chromosome, including the copper- and zinc-containing superoxide dismutase enzyme (CuZnSOD); indeed, one-and-a-half times the normal CuZnSOD activity is found in cells from trisomy 21 individuals [7]. It is possible that some of the characteristic features of Down's syndrome may be related to increased levels of CuZnSOD. Not only do transgenic mice over-expressing human CuZnSOD show many of the neurological and neurochemical features that are seen in human Down's syndrome, but they also have ocular lenses which are more susceptible to photochemical damage in vitro [7, 8]. Elevated levels of CuZnSOD may exacerbate the pro-oxidant effects of this enzyme; in the presence of millimolar concentrations of hydrogen peroxide, CuZnSOD can generate hydroxyl free radicals, and can catalyze the oxidation of azide, urate and nitrite (to the reactive nitrogen species NO2) [6, 7]. Down's syndrome individuals have indeed been found to have increased erythrocyte superoxide dismutase activity compared with control subjects [9], high levels of which, in non-Down's syndrome individuals, have been found to be associated with increased risk of cataract [10].

In light of the increased levels of superoxide dismutase (and therefore increased levels of hydrogen peroxide and other reactive species) associated with Down's syndrome, it seems possible that antioxidant therapy might be helpful in preventing cataractogenesis in this group of individuals. Indeed, Dickinson and Singh have previously suggested that vitamin E, and possibly vitamin C, may be used as a therapy in the treatment of the dementia associated with Down's syndrome, since they may modify the damage caused by excessive hydrogen peroxide production [6].

Conclusion

Compared with the general population, the prevalence of cataract in Down's syndrome was raised in those aged 45 to 64, but not in those aged 65 to 75 years. The increased prevalence of cataract may be the result of increased levels of CuZnSOD, in turn resulting from the location of the associated five exons of SOD1 on chromosome 21. These elevated levels of superoxide dismutase may give rise to increased levels of reactive species, including hydrogen peroxide and hydroxyl radicals, which may increase the risk of cataractogenesis. Therefore, nutritional supplementation with vitamin E, and possibly vitamin C, may help reduce the prevalence of cataract in Down's syndrome.

Declarations

Authors’ Affiliations

(1)
MRI Unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Imperial College London, Hammersmith Hospital
(2)
Mental Health Unit, Hillingdon Hospital

References

  1. Leibowitz HM, Krueger DE, Maunder LR, Milton RC, Kini MM, Kahn HA, Nickerson RJ, Pool J, Colton TL, Ganley JP, et al: The Framingham Eye Study monograph: An ophthalmological and epidemiological study of cataract, glaucoma, diabetic retinopathy, macular degeneration, and visual acuity in a general population of 2631 adults, 1973–1975. Surv Ophthalmol. 1980, 24 (Suppl): 335-610.PubMedGoogle Scholar
  2. Klein BE, Klein R: Cataracts and macular degeneration in older Americans. Arch Ophthalmol. 1982, 100: 571-573.View ArticlePubMedGoogle Scholar
  3. Gibson JM, Rosenthal AR, Lavery J: A study of the prevalence of eye disease in the elderly in an English community. Trans Ophthalmol Soc U K. 1985, 104: 196-203.PubMedGoogle Scholar
  4. Aitchison C, Easty DL, Jancar J: Eye abnormalities in the mentally handicapped. J Ment Defic Res. 1990, 34: 41-48.PubMedGoogle Scholar
  5. Das BN, Thompson JR, Patel R, Rosenthal AR: The prevalence of eye disease in Leicester – a comparison of adults of Asian and European descent. J R Soc Med. 1994, 87: 219-222.PubMed CentralPubMedGoogle Scholar
  6. Dickinson MJ, Singh I: Down's syndrome, dementia, and superoxide dismutase. Br J Psychiatry. 1993, 162: 811-817.View ArticlePubMedGoogle Scholar
  7. Halliwell B, Gutteridge JMC: Free Radicals in Biology and Medicine. 2007, Oxford: Oxford University Press, 4Google Scholar
  8. Groner Y, Elroy-Stein O, Avraham KB, Yarom R, Schickler M, Knobler H, Rotman G: Down syndrome clinical symptoms are manifested in transfected cells and transgenic mice overexpressing the human Cu/Zn-superoxide dismutase gene. J Physiol (Paris). 1990, 84: 53-77.Google Scholar
  9. Cengiz M, Seven M, Suyugül N: Antioxidant system in Down syndrome: a possible role in cataractogenesis. Genet Couns. 2002, 13: 339-342.PubMedGoogle Scholar
  10. Delcourt C, Cristol JP, Léger CL, Descomps B, Papoz L: Associations of antioxidant enzymes with cataract and age-related macular degeneration. The POLA Study. Pathologies Oculaires Liées à l'Age. Ophthalmology. 1999, 106: 215-222. 10.1016/S0161-6420(99)90059-3.View ArticlePubMedGoogle Scholar
  11. Lowe R: The eyes in mongolism. Br J Ophthalmol. 1949, 33: 131-174. 10.1136/bjo.33.3.131.PubMed CentralView ArticlePubMedGoogle Scholar
  12. Skeller E, Øster J: Eye symptoms in mongolism. Acta Ophthalmol (Copenh). 1951, 29: 149-161.View ArticleGoogle Scholar
  13. Cullen JF, Butler HG: Mongolism (Down's syndrome) and keratoconus. Br J Ophthalmol. 1963, 47: 321-330. 10.1136/bjo.47.6.321.PubMed CentralView ArticlePubMedGoogle Scholar
  14. Chutko SM: Ophthalmological findings in Down's disease. Vestn Oftalmol. 1965, 78: 68-73.PubMedGoogle Scholar
  15. Rochels R, Nover A, Schmid F: Ophthalmologische symptome beim Mongolismussyndrom. Albrecht Von Graefes Arch Klin Exp Ophthalmol. 1977, 205: 9-22. 10.1007/BF00413458.View ArticlePubMedGoogle Scholar
  16. Gnad HD, Rett A: Ophthalmologische symptome beim Down syndrom. Wien Klin Wochenschr. 1979, 91: 735-737.PubMedGoogle Scholar
  17. Jaeger EA: Ocular findings in Down's syndrome. Trans Am Ophthalmol Soc. 1980, 78: 808-845.PubMed CentralPubMedGoogle Scholar
  18. Walsh SZ: Keratoconus and blindness in 469 institutionalized subjects with Down's syndrome and other causes of mental retardation. J Ment Defic Res. 1981, 25: 243-251.PubMedGoogle Scholar
  19. Shapiro MB, France TD: The ocular features of Down's syndrome. Am J Ophthalmol. 1985, 99: 659-663.View ArticlePubMedGoogle Scholar
  20. Riise R: Synsfunksjonen ved Down's syndrom. Tidsskr Nor Laegeforen. 1986, 106: 317-319.PubMedGoogle Scholar
  21. Hestnes A, Sand T, Fostad K: Ocular findings in Down's syndrome. J Ment Defic Res. 1991, 35: 194-203.PubMedGoogle Scholar
  22. Da Cunha RP, Moreira JB: Ocular findings in Down's syndrome. Am J Ophthalmol. 1996, 122: 236-244.View ArticlePubMedGoogle Scholar

Copyright

© Puri and Singh; licensee BioMed Central Ltd. 2007

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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