In addition, some of these genes in Group 3 (FNDC3B, COL5A1, COL6A1), together with genes in Group 2 (IGFBP5, FGF9, and CWC27/ADAMT6) was linked to connective tissue disorder (Supplementary Fig. 6) and has been associated with keratoconus29,68–71, a disorder of corneal thinning and steepening, implying a possible effect of CC genes regulating refractive error and keratoconus. This evidence concerns the gene COL5A1 and keratoconus.