Objective: To understand the sites of macular dysfunction in retinitis pigmentosa (RP) by evaluating local electroretinogram (LERG) and further evaluating fundamental and second harmonic components.
Methods: LERG were recorded in 98 eyes of 49 patients to a flickered sinusoid of 31Hz and 10Hz with a hand-held stimulator with direct visualization of the fundus through dilated pupils.
Results: Compared to controls, the patients showed losses of both fundamental and second harmonic amplitudes. The abnormality ratios of fundamental amplitudes in RP affected time < 5 years, 5 - 15 years, 15 - 25 years and > 25 years were 54%, 64%, 83% and 92% respectively; and the abnormality ratios of second harmonic amplitudes were 18%, 36%, 58% and 75% respectively. The fundamental-second harmonic ratio was much more higher in the autosomal recessive and sporadic patients than in the autosomal dominant patients (P < 0.01). On average, the fundamental-second harmonic ratio in the patients tended to increase with age.
Conclusion: The results suggest that in the retinitis pigmentosa, both receptoral and postreceptoral sites contribute to macular dysfunction. The level of macular dysfunction in different types of hereditary patients is different. It would be of clinical value to obtain a fundamental-second harmonic ratio in order to assess the disturbance in different sites of macular.