Published online April 1, 2008
PEDIATRICS Vol. 121 No. 4 April 2008, pp. 863 (doi:10.1542/peds.2008-0099)

This Article Extract Full Text (PDF) Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services E-mail this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Request Permissions Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Tapp, R. J. Articles by Williams, C. Search for Related Content PubMed Articles by Tapp, R. J. Articles by Williams, C. Related Collections Heart & Blood Vessels Social Bookmarking                         What's this?

LETTER TO THE EDITOR

Low Birth Weight and Retinal Vascular Caliber in Young Children: In Reply

Robyn J. Tapp
International Centre for Circulatory Health, NHLI
St Mary's Hospital & Imperial College London
London W2 1LA, United Kingdom
Department of Epidemiology and Preventive Medicine
Monash University
Melbourne, Victoria 3002
Australia

Nicholas Witt
Nish Chaturvedi
Richard Evans
Simon A. Thom
Alun D. Hughes
International Centre for Circulatory Health, NHLI
St Mary's Hospital & Imperial College London
London W2 1LA, United Kingdom

Andrew Ness
Department of Social Medicine, University of Bristol
Bristol BS1 2LY, United Kingdom

Cathy Williams
Centre for Child and Adolescent Health, University of Bristol
Bristol BS1 2LY, United Kingdom

We thank Cheung et al¹ for their comments on our recent article examining the impact of small birth size on measures of the microvasculature. The findings of our study using novel measures of the retinal vasculature (tortuosity and bifurcation optimality deviance: a measure of endothelial function) in children aged 12 years support the hypothesis that early life factors may have an important impact on vascular structure, possibly through an adverse effect on endothelial function.

Since acceptance of our study for publication, Cheung et al¹ have also reported a study examining the association between birth weight and quantitative measures of the retinal vasculature in Singaporean children aged 7 to 9 years. The findings of Cheung et al's¹ study are consistent with our own in that both studies showed no association between birth weight and venular diameter.² However, in both studies the analyses did not account for the effects of ocular magnification. We agree that this is an important issue, especially given the high prevalence of myopia (75.7%) in the population of Singaporean children. We are grateful to Cheung et al¹ for sharing their new data that show a strong association between wider retinal venular diameter and decreased birth weight once ocular magnification is taken into account. Their suggestion that we undertake a similar analysis in the ALSPAC cohort is valuable and well made.

Autorefraction data for the ALSPAC children are available; however, there are limitations to its use, because the measures were collected without cycloplegia. This method can result in significant errors in the quantification of refractive error in children, where there is a tendency to overestimate myopia and underestimate hypermetropia.^3–5 Because the magnitude of the error is proportional to the true refractive error, it is not possible to use transformations or simple adjustments to make the data more valid. We have examined the quality of these noncycloplegic autorefraction data in a subset of ALSPAC children and reported that they may be more useful to indicate the presence, rather than the amount, of clinically important refractive errors.⁶ We are currently collecting higher-quality refraction and axial length data and may be able to incorporate these in future analyses. We would once again like to thank Cheung et al¹ for their letter and suggestion.

REFERENCES

1. Cheung N, Islam FM, Saw SM, et al. Distribution and associations of retinal vascular caliber with ethnicity, gender, and birth parameters in young children. Invest Ophthalmol Vis Sci. 2007;48 (3):1018 –1024[Abstract/Free Full Text]

2. Tapp RJ, Williams C, Witt N, et al. Impact of size at birth on the microvasculature: the Avon Longitudinal Study of Parents and Children. Pediatrics. 2007;120 (5). Available at: www.pediatrics.org/cgi/content/full/120/5/e1225

3. Isenberg SJ, Del Signore M, Madani-Becker G. Use of the HARK autorefractor in children. Am J Ophthalmol. 2001;131 (4):438 –441[CrossRef][Web of Science][Medline]

4. Zhao J, Mao J, Luo R, Li F, Pokharel GP, Ellwein LB. Accuracy of noncycloplegic autorefraction in school-age children in China. Optom Vis Sci. 2004;81 (1):49 –55[CrossRef][Web of Science][Medline]

5. Fotedar R, Rochtchina E, Morgan I, Wang JJ, Mitchell P, Rose KA. Necessity of cycloplegia for assessing refractive error in 12-year-old children: a population-based study. Am J Ophthalmol. 2007;144 (2):307 –309[CrossRef][Web of Science][Medline]

6. Williams C, Miller LL, Northstone K, Sparrow JM. The use of non-cycloplegic autorefraction data in general studies of children's development. Br J Opthalmol. In press

---

PEDIATRICS (ISSN 1098-4275). ©2008 by the American Academy of Pediatrics

CiteULike    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

This Article Extract Full Text (PDF) Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services E-mail this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Request Permissions Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Tapp, R. J. Articles by Williams, C. Search for Related Content PubMed Articles by Tapp, R. J. Articles by Williams, C. Related Collections Heart & Blood Vessels Social Bookmarking                         What's this?