Table 1. Time period (years) required to detect various rates of MD change with 80% power in visual fields with low, moderate and high degrees of variability with one (a), two (b) and three (c) examination per year.

(a) 1 examination/year Progression rate (dB/year)	Variability
	Low	Moderate	High
−0.25	13	19	30
−0.5	9	13	19
−1.0	6	9	13
−2.0	5	6	9

(b) 2 examinations/year Progression rate (dB/year)	Variability
	Low	Moderate	High
−0.25	6.5	8.5	15
−0.5	4.5	6.5	8.5
−1.0	3	4.5	6.5
−2.0	2.5	3	4.5

(c) 3 examinations/year Progression rate (dB/year)	Variability
	Low	Moderate	High
−0.25	4.3	6.3	10
−0.5	3	4.3	6.3
−1.0	2	3	4.3
−2.0	1.7	2	3