Retinal nerve fiber layer defects are a defining feature of optic neuropathies and have been implicated in several neurodegenerative disorders, including multiple sclerosis, Alzheimer’s disease, and Parkinson’s disease. Both maternal smoking during pregnancy and low birth weight have been implicated in impaired development of the retina.
The Copenhagen Child Cohort 2000 Eye Study
Mr. Ashina and colleagues sought to investigate the associations of maternal smoking during pregnancy and low birth weight with retinal nerve fiber layer thickness in preadolescent children. They examined data from a prospective, population-based, birth cohort study that included all children (n = 6,090) born in 2000 in Copenhagen. Maternal smoking data were collected through parental interviews. Birth weight, pregnancy, and medical history data were obtained from the Danish Medical Birth Registry. As a follow-up, the researchers performed eye examinations on 1,406 of these children from May 1, 2011, to October 31, 2012, when the children were age 11 or 12.
Of the 1,406 children in the study, 1,323 were included in the analysis. Mean age was 11.7. Nearly half of the children (47.8%) were boys. The mean retinal nerve fiber layer thickness was 104 mm. In 227 children whose mothers had smoked during pregnancy, the peripapillary retinal nerve fiber layer was 5.7 mm thinner than in children whose mothers had not smoked during pregnancy, after adjusting for age, sex, birth weight, height, body weight, Tanner stage of pubertal development, axial length, and spherical equivalent refractive error. In children with low birth weight (ie, < 2,500 g), the retinal nerve fiber layer was 3.5 mm thinner than in children with normal birth weight, after adjustment for all variables.
“The results of this study add evidence to existing recommendations to avoid smoking during pregnancy and support measures that promote maternal and fetal health,” the researchers said.
A Public Health Message
In an invited commentary that accompanied the study, Christopher Kai-Shun Leung, MD, from the Department of Ophthalmology and Visual Sciences at Hong Kong Eye Hospital and Chinese University of Hong Kong in Kowloon, said that “although a difference of 5 to 6 mm in average circumpapillary retinal nerve fiber layer thickness is unlikely to translate into a detectable difference in visual function in children aged 12 to 13 years, the risk of subsequent development of visual impairment should not be overlooked.” Furthermore, he noted, “whether a thinner retinal nerve fiber layer in the children of mothers who smoked during pregnancy will increase the risk of developing optic neuropathies and neurodegenerative disorders is an important question for future studies.”
—Glenn S. Williams
Ashina H, Li XQ, Olsen EM, et al. Association of maternal smoking during pregnancy and birth weight with retinal nerve fiber layer thickness in children aged 11 or 12 years: The Copenhagen Child Cohort 2000 Eye Study. JAMA Ophthalmol. 2017 March 2 [Epub ahead of print].
Leung CK. Evaluation of retinal nerve fiber layer thinning with Fourier-domain optical coherence tomography. JAMA Ophthalmol. 2017 March 2 [Epub ahead of print].