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 μv, -158 ± 63 μv, 345 ± 105 μv, -20 ± 11 μv, and 42 ± 21 μv, respectively, whereas those of patients with loHM were 252 ± 77 μv, -235 ± 60 μv, 464 ± 65 μv, -36 ± 9 μv, and 104 ± 26 μv, 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.