Figure 8.
Regression of cone ERG amplitude on age among 1039 patients with retinitis pigmentosa in the database of the Berman-Gund Laboratory. Patients were followed for 3–29 years with at least 2 visits separated by 3 or more years. The average rate of decline over the long-term can be described by an exponential function with a mean rate of loss of 8.1% of remaining cone function per year. The rate of decline can also be described by a spline model. Goodness of fit of the exponential model did not significantly differ from that of the spline model.