Cone-Rod Dysfunction Is a Sign of Early-Onset High Myopia

Purpose. High myopia (HM) is one of the leading causes of irreversible blindness because of its associated complications. Early-onset HM (eoHM) that presents before primary school age may be genetically determined, whereas late-onset HM (loHM) is affected by genetic and environmental factors. Identification of signs that differentiate eoHM from loHM may provide valuable clues toward understanding the molecular basis of HM. Methods. In this study, 42 subjects with HM were recruited, including 32 eoHM (onset age, <= 5 years) and 10 loHM (onset age, 12.4 +/- 2.5 years). Clinical data from these two groups were compared, including best visual acuity, refraction, axial length, and electroretinography. Results. The mean amplitudes of rod b-wave, maximum a-wave, maximum b-wave, cone a-wave, and cone b-wave of patients with eoHM were 179 +/- 72 mu v, -158 +/- 63 mu v, 345 +/- 105 mu v, -20 +/- 11 mu v, and 42 +/- 21 mu v, respectively, whereas those of patients with loHM were 252 +/- 77 mu v, -235 +/- 60 mu v, 464 +/- 65 mu v, -36 +/- 9 mu v, and 104 +/- 26 mu v, respectively (p < 0.001). Patients with eoHM had significantly reduced responses of cones and rods, especially cones, as compared with patients with loHM. The cone-rod responses in patients with loHM were within normal range. Conclusions. The findings suggest that cone-rod dysfunction may be a sign for eoHM compared with loHM.