Development and evaluation of a linear staircase strategy for the measurement of perimetric sensitivity

Perimetric sensitivity of patients with glaucoma has traditionally been measured in logarithmic (dB) units, but linear sensitivity correlates better with conventional structural measures of glaucomatous damage. Monte Carlo simulations of perimetric algorithms were used to assess potential effects of logarithmic steps on bias and variability when perimetric sensitivity was represented in linear units, and to assess the potential benefits of algorithms using linear steps. Simulations predicted that linear staircases could reduce the sensitivity-dependence of bias, variability and efficiency. These predictions were supported by a perimetric study of 21 patients with glaucoma and 20 age-similar controls who made repeat visits over several weeks.