Comparison of electroretinogram between healthy preterm and term infants

Abstract

To investigate the retinal development in healthy preterm infants through standard ganzfeld electroretinograms (ERG) and compare the difference of ERG between the healthy preterm and term infants. Forty-nine 49 healthy infants were recruited to this study, including 20 preterm and 29 term infants. All the infants were grouped as follows: term 40W group (ERG recorded at birth), term 44W group (ERG recorded at 4weeks after birth), preterm 35W group (ERG recorded at birth) and preterm 40W group (ERG recorded at due date). Standard ganzfeld flash ERG was performed according to the ISCEV standard for the clinical electroretinogram (2008). The ERG amplitudes in the term 44W group were notably larger than those of the term 40W group, but there was no significant difference between the two groups for combined-b and cone-b responses. The implicit time of cone-b, combined-a and 30Hz in term 44W group was significantly shorter than that in term 40W group, and there was no significant difference in other ERG responses between the two groups. Amplitude of ERG waves in preterm 35W group was only 48.7-78.0% of that in term 40W group, and the difference of all ERG waves between the two groups was statistically significant, but there was no significant difference between the two groups for implicit time of all responses except rod-b. There was no significant difference between the amplitude of ERG waves in term 40W and preterm 40W groups; however, implicit time of cone-a and cone-b in term 40W is significantly longer than that in preterm 40W group. The ERG amplitudes in the preterm 35W group were notably smaller than those of the preterm 40W group, and except cone-a response, the difference between the two groups was statistically significant, while the difference of the implicit time between the two groups was not significant. OPs could not be recorded in some infants. OPs were seen significantly less frequently in the preterm 35W group than in either the term 40W group (Fisher exact test, P=0.006) or the term 44W group (Fisher exact test, P=0.02). No other significant inter-group frequency differences were found. The mean amplitude ratio b/a was not significantly different between the four groups (P>0.05) (analysis of variance). The retina is not fully developed at birth in healthy preterm infants. The preterm ISCEV ERG matures rapidly after birth and by term reaches the degree of maturation found in term born neonates.