Visual problems in people with severe mental handicap

Visual dysfunctions and ocular disorders in children with developmental delay. II. Aspects of refractive errors, strabismus and contrast sensitivity

PURPOSE

To evaluate the prevalence of refractive errors, strabismus and reduced contrast sensitivity in an unselected group of children with developmental delay (DD), and to propose extensions to the existing guidelines to assess the number of examinations required to optimally support children with DD.

METHODS

A total of 923 children with IQ < or = 80, aged 4-15 years, from Copenhagen County, Denmark, were ophthalmically examined. The prevalence of refractive errors and strabismus and the presence of reduced contrast sensitivity were recorded and related to level of IQ.

RESULTS

Among the 923 children, the following prevalences were found: significant hyperopia (> or = + 3 D) 15.3%; myopia (< - 0.5 D) 10.8%, and astigmatism (< - 1 cyl D) 20.6%. Strabismus was found in 26.8% of subjects (esotropia in 14.9%, exotropia in 10.3%, and other forms, including mixed types, in 1.6%). Refractive errors and strabismus were significantly correlated with low IQ. Reduced contrast sensitivity was correlated with age, visual acuity and level of IQ.

CONCLUSIONS

To our knowledge, this study is the largest on ocular disorders in children with DD. Hyperopia, astigmatism, anisometropia, strabismus and contrast sensitivity had a high prevalence, and all disorders were related to low IQ. According to the extended guidelines, an annual minimum of 565 examinations per 100 000 children (0-17 years) is required to optimally support children with DD.

6,220 institutionalised people with intellectual disability referred for visual assessment between 1993 and 2003: overview and trends

AIMS

To summarise the results of visual performance tests and other data of institutionalised people with intellectual disability referred to a visual advisory centre (VAC) between 1993 and 2003, and to determine trends in these data.

METHODS

A retrospective medical record review was undertaken of 6,220 consecutive people examined ophthalmologically according to a standard protocol by one VAC that specialised in visual assessment and treatment of people with intellectual disability, between 1993 and 2003. chi2 test for linear trend was used and linear regression coefficients were calculated.

RESULTS

The proportion of people aged > or =50 years increased from 19.3% to 34.2% between 1995 and 2003 (p<0.001); the combined figure of severe or profound intellectual disability decreased from 80.0% to 52.6% (p<0.001); the proportion of mobile people increased from 52.1% to 98.0% (p<0.001); the combined proportion of people with visual impairment or blindness decreased from 70.9% to 22.9% (p<0.001), and that of people with visual disorders decreased from 89.6% to 75.3% (p<0.001). Causes of intellectual disability were identified in 58.4% people; 20.8% had Down's syndrome.

CONCLUSION

Many ocular diagnoses were found, indicating the need for ophthalmological monitoring. Specialised centres are helpful, because assessment and treatment of people with intellectual disability is complicated and time consuming. Protocols for efficient referral will have to be developed. A major task lies ahead to improve the treatment rates of refractive errors, cataract and strabismus, and to find specific causes of intellectual disability.