Kong M, Hwang SS, Ko H, et al. - In this investigation involving 361 Korean adults from 89 families with normal healthy eyes, researchers sought to assess the genetic influence on macular ganglion cell inner plexiform layer (GCIPL) thickness. They measured macular GCIPL thickness with optical coherence tomography in nine macular subfields defined by the E TDRS. The authors discovered that GCIPL thickness was highest in inner subfields and lowest in fovea. Monozygotic twin pairs exhibited significantly higher ICCs of GCIPL thickness in all subfields vs those in parent-offspring pairs and sibling pairs. Heritability of GCIPL thickness in outer subfields for superior, inferior, temporal, and nasal fields, respectively, was 0.69, 0.67, 0.72, and 0.68. Heritability of GCIPL thickness in inner subfields for superior, inferior, temporal, and nasal subfields, respectively, was 0.55, 0.56, 0.75, and 050. Macular GCIPL thickness is affected greatly by genetic factors. It differs according to subfields with moderate to high heritability in all subfields.