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Original Investigation
August 2017

Reduction of Rod and Cone Function in 6.5-Year-Old Children Born Extremely Preterm

Author Affiliations
  • 1Department of Neuroscience/Ophthalmology, Uppsala University, Uppsala, Sweden
  • 2Department of Ophthalmology, Lund University, Lund, Sweden
JAMA Ophthalmol. 2017;135(8):854-861. doi:10.1001/jamaophthalmol.2017.2069
Key Points

Question  How does extreme preterm birth affect retinal function in children who are 6.5 years of age?

Findings  In this subcohort study of the Extremely Preterm Infants in Sweden Study, children 6.5 years of age who were born extremely preterm (<27 weeks’ gestational age) had reduced function of both rods and cones when compared with children born at term, according to full-field electroretinography recordings.

Meaning  A reduced function of both rods and cones is reported in children born extremely preterm, compared with children born at term, which may contribute to the various visual problems of this new population as they age.

Abstract

Importance  The function of rods and cones in children born extremely preterm has not yet been fully investigated.

Objective  To compare retinal function via full-field electroretinographic (ffERG) recordings in 6.5-year-old children born extremely preterm with children born at term.

Design, Setting, and Participants  A subcohort study was conducted from July 1, 2010, to January 15, 2014, of the national Extremely Preterm Infants in Sweden Study, including preterm children (<27 weeks’ gestational age) and children born at term, at 6.5 years of age and living in the Uppsala health care region in Sweden. Full-field electroretinography was performed binocularly, using DTL electrodes and electroretinographic (ERG) protocols with flash strengths of 0.009, 0.17, 3.0, and 12.0 candelas (cd)/s/m2, together with 30-Hz flicker and 3.0 cd/s/m2 single-cone flash.

Main Outcomes and Measures  The ffERG recordings were analyzed, and their associations with gestational age and retinopathy of prematurity were examined.

Results  Adequate ffERG recordings were obtained from 52 preterm children (19 girls and 33 boys; mean [SD] age at examination, 6.6 [0.1] years) and 45 children born at term (22 girls and 23 boys; mean [SD] age at examination, 6.6 [0.1] years). Lower amplitudes of the combined rod and cone responses (the a-wave of the dark-adapted ERG protocol of 3.0 cd/s/m2: mean difference, –48.9 μV [95% CI, –80.0 to –17.9 μV]; P=.003; the a-wave of the dark-adapted ERG protocol of 12.0 cd/s/m2: mean difference, –55.7 μV [95% CI, –92.5 to –18.8 μV]; P = .004), as well as of the isolated cone response (30-Hz flicker ERG: mean difference, –12.1 μV [95% CI, –22.5 to –1.6 μV]; P = .03), were found in the preterm group in comparison with the group born at term. The implicit time of the combined rod and cone responses (the a-wave of the dark-adapted ERG protocol of 12.0 cd/s/m2) was longer (mean difference, 1.2 milliseconds [95% CI, 0.3-2.0 milliseconds]; P = .01) in the preterm group, as were the isolated cone responses (30-Hz flicker ERG: mean difference, 1.2 milliseconds [95% CI, 0.5-1.8 milliseconds]; P < .001), than in the group born at term. No association was found between the ffERG recordings and gestational age or retinopathy of prematurity in the preterm group.

Conclusions and Relevance  Both rod function and cone function were reduced in children born extremely preterm when compared with children born at term. There was no association with retinopathy of prematurity in the preterm group, which suggests that being born extremely preterm may be one of the main reasons for a general retinal dysfunction.

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