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

Anna E C Molnar¹, Sten O Andréasson², Eva K B Larsson¹

¹Department of Neuroscience/Ophthalmology, Uppsala University, Uppsala, Sweden.

JAMA Ophthalmology

|June 30, 2017

Insights

Children born extremely preterm show reduced rod and cone function compared to full-term infants. This retinal dysfunction appears linked to prematurity itself, not retinopathy of prematurity.

Area of Science:

Ophthalmology
Neonatology
Developmental Neuroscience

Background:

The visual function of extremely preterm infants is not well understood.
Rods and cones are critical for vision, but their function in this population needs further investigation.

Purpose of the Study:

To compare retinal function in 6.5-year-old children born extremely preterm versus those born at term.
To assess rod and cone function using full-field electroretinography (ffERG).

Main Methods:

A subcohort study included extremely preterm (<27 weeks GA) and term-born children at 6.5 years.
Full-field electroretinography (ffERG) was performed using specific flash strengths and flicker protocols.
ERG recordings were analyzed for associations with gestational age and retinopathy of prematurity.

Main Results:

Extremely preterm children exhibited lower amplitudes in both rod-cone responses and isolated cone responses compared to term-born children.
The implicit time for both rod-cone and cone responses was longer in the preterm group.
No significant association was found between ffERG findings and gestational age or retinopathy of prematurity.

Conclusions:

Children born extremely preterm have impaired rod and cone function at age 6.5.
The observed retinal dysfunction is likely a direct consequence of extreme prematurity.
This suggests prematurity itself is a significant factor in general retinal dysfunction.

Read full analysis

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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