Modulation transfer function and critical flicker frequency in high myopia patients

Background and purpose: Critical flicker frequency (CFF) decreases due to optic nerve and retinal damage in patients with optic neuritis or glaucoma. Because retinal degeneration is also found in high myopia, we investigated whether the modulation transfer function (MTF) and CFF are altered in patients with high myopia. Methods: Forty-six patients with high myopia (< -8 diopters, D) were recruited from our outpatient department. The control group comprised 21 young volunteers with myopia of 8 to -2 D. The myopic and control groups were similar in terms of age and sex. Results: At all frequencies tested, the myopic group had lower CFF and higher modulation values than the control group. The mean CFF was significantly lower in myopic patients (46.8 +/- 9.0 Hz) than in control subjects (52.5 +/- 4.4 Hz). Patients with extremely high myopia (< -10 D) had significantly greater modulation values at 5, 10, 15, 55 and 60 Hz than those with moderately high myopia (-8 D to -10 D). The CFF did not differ significantly between those with extremely high (46.3 +/- 8.8 Hz) and those with moderately high (49.0 +/- 6.9 Hz) myopia. Conclusions: The findings of this study support that the CFF decreases and MTF increases in patients with high myopia, and that the alternation of MTF is related to the degree of myopia. CFF and MTF may, therefore, have potential as indexes to evaluate the severity of retinal degeneration in patients with high myopia.