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Visual screening of children in Sweden: epidemiological and methodological aspects
Linköping University, Department of Neuroscience and Locomotion, Ophthalmology. Linköping University, Faculty of Health Sciences.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to assess the vision screening system and ocular status in Sweden of today, yesterday and tomorrow and to compare the prevalence of ocular disease before and after screening and treatment with special focus on amblyopia.

Screening has been defmed by the United States Commission of Chronic Illness (1957) as "the presumptive identification of unrecognized disease or defect by the application oftests, examinations or other procedures, which can be rapidly applied. Screening tests sort out apparently well persons who probably have a disease from those who probably do not". The screening system for eye disorders was introduced in the whole country in the beginning of 1970 and has not been evaluated in a greater area and for a longer period. Neither has an evaluation been done according to WHO's instructions. Amblyopia is the most common cause to visual impairment in one eye. The visual system is developing mostly in the first years of life and it is important to treat amblyopia in early childhood. The three first papers are retrospective studies and the fourth a prospective study. The study group in the first and second paper consisted of all children born 1982 in three Swedish cities from newborn until the age of 10 years. The children have been tested eight to nine times at the Child Health Care Centres and in school during this time. The sensitivity and specificity of visual screening were 92% and 97% respectively. The prevalence of ametropia was 7.7%, strabismus 3.1%, amblyopia ≤ 7 2.9% and organic lesions 0.2%. We compared the prevalence of amblyopia today with the time before screening was introduced in Sweden. This comparison shows that serious amblyopia has been reduced about 10 times with screening and treatment.

Loss of vision in the non-amblyopic eye was investigated by studying patients with amblyopia at four visual rehabilitation centres. Approximately 1.2% of the people with amblyopia ≤ 0.3 will eventually become visually handicapped due to lesions in the better eye.

Despite visual screening and treatment there are some children left with residual amblyopia. We investigated ways to improve the system by lowering the age for visual acuity examination from 4 to 3 years and at the same time two vision charts were compared. We found that the testability rate for 3-year-olds was almost the same for the Lea Symbol chart and the HVOT chart (82.8% and 84.8% respectively). Testability was about 10% higher at 4 years. The positive predictive value was lower at 3 years (58%) than has previously been found at 4 years (72%).

Conclusion: In these studies we have found that screening is justified for the following reasons: visual screening is efficient in terms of sensitivity and specificity and many important ocular conditions are detected in this process; the prevalence of serious amblyopia is greatly reduced by screening and treatment; loss of vision in the non-amblyopic eye is a significant problem, which can be greatly reduced by screening and treatment, thereby saving expenses for the society.

The following has been found regarding the design of visual screening: visual acuity testing is efficient in detecting visual disorders from 4 years and up; visual acuity can be tested at 3 years, but with lower positive predictive value; the most widely used charts in Sweden and internationally, the HVOT chart and the Lea Symbols chart perform equally well in visual acuity testing of 3-year-old and 4-year-old children.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2004. , 40 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 852
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-23541Local ID: 3012OAI: oai:DiVA.org:liu-23541DiVA: diva2:243855
Public defence
2004-05-28, Hälsans Hus, aulan, Hälsouniversitet, Linköping, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-10-30Bibliographically approved
List of papers
1. Screening for visual and ocular disorders in children, evaluation of the system in Sweden
Open this publication in new window or tab >>Screening for visual and ocular disorders in children, evaluation of the system in Sweden
1998 (English)In: Acta Paediatrica, ISSN 0803-5253, E-ISSN 1651-2227, Vol. 87, no 11, 1173-1179 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to evaluate the visual screening system in Sweden. We have made a retrospective investigation of the results of screening for ocular disease and visual impairment of all children born in 1982 in three Swedish communities. The records from screening examinations from 0 to 10 y and from diagnostic follow-up at the departments of ophthalmology that the children were referred to were inspected. The data were used to evaluate the efficiency of the Swedish visual screening system. The study included 3126 children. The attendance rate at the 4-y examination was better than 99%. The sensitivity of the 4- and 5.5-y screening examinations was on the average 92% and the specificity was 97%. The average number of false negative cases at 4 y was 5.6 in 1000 (0.56%). With this screening and subsequent diagnosis and treatment, the prevalence of amblyopia at different levels of visual acuity at the age of 10 y was: 0.06% with visual acuity <0.1,0.9% with visual acuity <0.5 and 1.7% with visual acuity < 0.7. In spite of largely unchanged pressure of amblyogenic factors in the population, the prevalence of deep and moderate amblyopia has been markedly reduced by screening and early treatment.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-84984 (URN)10.1111/j.1651-2227.1998.tb00926.x (DOI)
Available from: 2012-10-30 Created: 2012-10-30 Last updated: 2017-12-07
2. Visual screening of Swedish children: an ophthalmological evaluation
Open this publication in new window or tab >>Visual screening of Swedish children: an ophthalmological evaluation
2001 (English)In: Acta Ophthalmologica Scandinavica, ISSN 1395-3907, E-ISSN 1600-0420, Vol. 79, no 3, 240-244 p.Article in journal (Refereed) Published
Abstract [en]

Purpose:This study describes the various ophthalmological conditions detected in the Swedish visual screening program for children.

Methods: The study was longitudinal and retrospective. All children (3126) born in 1982 in three Swedish municipalities have been followed from birth to ten years of age. Visual acuity was examined at the ages of 4, 5.5, 7 and 10 years. Before the age of 4, a gross examination of the eyes was performed.

Results: The prevalence of ametropia in the population was 7.7%, the prevalence of strabismus 3.1%, and the prevalence of organic lesions 0.6%. Seven children (0.2%) were visually handicapped (visual acuity ≤0.3 in the better eye). Refractive errors and microtropias were mainly detected at the age of 4, when the first visual acuity test was performed, while manifest strabismus was in many cases detected before this age. With this screening and subsequent diagnosis and treatment, the prevalence of deep amblyopia (visual acuity ≤0.3) has been reduced from 2% to 0.2%. With treatment, 47% of the amblyopic children achieved a visual acuity better than 0.7.

Conclusion: Visual screening is effective in detecting visual and ocular disorders. Most conditions are discovered before the age of 6. Compared to an unscreened population, the prevalence of amblyopia is greatly reduced.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-27825 (URN)10.1034/j.1600-0420.2001.790306.x (DOI)12580 (Local ID)12580 (Archive number)12580 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13
3. The frequency of amblyopia among visually impaired persons
Open this publication in new window or tab >>The frequency of amblyopia among visually impaired persons
Show others...
2002 (English)In: Acta Ophthalmologica Scandinavica, ISSN 1395-3907, E-ISSN 1600-0420, Vol. 80, no 1, 44-46 p.Article in journal (Refereed) Published
Abstract [en]

Purpose: To investigate the frequency of amblyopia among visually handicapped patients.

Methods: The study is a retrospective investigation of all living patients registered in four Visual Rehabilitation Centres in a region in southern Sweden. The area's total population numbered 865,612 persons of whom 11,365 were registered as visually handicapped (with visual acuity ≤ 0.3 in the better eye).

Results: Amblyopia was the main cause of decreased visual acuity in one eye in 1.72% (195 of 11,365) of the patients. The average age of the patients with amblyopia was 69 years (9−95 years) and 28.2% of these patients were less than 65 years old (the age for retirement in Sweden).

The median visual acuity in the amblyopic eye among these patients was 0.1. The median visual acuity in the nonamblyopic eye was 0.2. The most common cause of decreased vision in the nonamblyopic eye was macular degeneration (39.5%). Bilateral amblyopia was present in 13 (6.7%) of the amblyopic patients. By comparing this study with earlier studies, we can calculate that about 1.2% of the persons with amblyopia 0.3 or lower will eventually become visually handicapped.

Conclusion: A small but considerable number of patients who attend the Visual Rehabilitation Centres have amblyopia as a cause of their visual impairment. Since amblyopia can be treated if detected in childhood, later visual rehabilitation of these patients can be avoided or delayed, thereby reducing rehabilition costs for society.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-27826 (URN)10.1034/j.1600-0420.2002.800109.x (DOI)12582 (Local ID)12582 (Archive number)12582 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13
4. Is vision screening in 3-year-old children feasible?: comparison between the Lea Symbol chart and the HVOT (LM) chart
Open this publication in new window or tab >>Is vision screening in 3-year-old children feasible?: comparison between the Lea Symbol chart and the HVOT (LM) chart
2005 (English)In: Acta Ophthalmologica Scandinavica, ISSN 1395-3907, E-ISSN 1600-0420, Vol. 83, no 1, 76-80 p.Article in journal (Refereed) Published
Abstract [en]

Purpose: The aim of this prospective study was to compare visual screening at the age of 3 years with screening at 4 years using two different charts.

Methods: A total of 478 3-year-old children were tested at four child health care centres (CHCCs). Of these children, 440 were tested again at the age of 4 years. A third group, a control group, consisting of 229 children, was examined only at the age of 4 years. All children were tested with both the HVOT chart and the Lea Symbol chart.

Results: Testability rates for 3-year-olds were almost the same with the Lea Symbol chart and the HVOT chart (82.8% and 84.8%, respectively). The corresponding rates for the same children tested at 4 years of age were 96.5% and 97.0%, and for the 4-year-olds not previously tested 92.9% and 92.8%. The mean testing time was somewhat shorter for the Lea Symbol chart in all three groups, but the difference was not statistically significant. The difference in the assessment of visual acuity between the two charts was small and less than 1/10th of a line. The positive predictive value was lower at 3 years (58%) than has previously been found at 4 years (74.6%).

Conclusion: Three-year-old children co-operate well in visual acuity testing. However, the examination time is a little longer and the testability rate is about 10% lower than at 4 years. Both 3-year-old and 4-year-old children can be tested equally well with the HVOT and the Lea Symbol charts.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-29995 (URN)10.1111/j.1600-0420.2005.00367.x (DOI)15435 (Local ID)15435 (Archive number)15435 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13

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