Macular Electroretinograms to Flicker and Pattern Stimulation in Lamellar Macular Holes

Steady-state macular (9 degrees x 9 degrees) electroretinograms in response to either sinusoidal flicker (focal electroretinogram) or counterphased sinusoidal gratings (pattern electroretinogram) were recorded in 14 patients with inner lamellar macular holes, in 4 patients with full-thickness macular holes and in 14 age-matched controls. Fourier analysis of focal and pattern electroretinograms yielded three main components: a first and a second harmonic to flicker, and a second harmonic to pattern. Recent evidence indicates that the first harmonic to flicker is of receptoral origin, whereas the flicker and pattern second harmonics represent, at least in part, the activity of different generators in the inner retina. When compared to controls, patients with inner lamellar holes showed significant amplitude reduction and phase delay for both flicker and pattern second harmonics, but not for the flicker first harmonic. Patients with full-thickness holes showed significant amplitude reduction also for the flicker first harmonic. These results indicate a prevalent functional involvement of the inner retina in lamellar macular holes, which can be clinically detected by evaluating focal and pattern electroretinogram second harmonics.