Table 2. Rates of visual field change corresponding to total change in mean deviation (MD) over 2, 3 and 5 years (a) and the number of visual fields per year required to detect the corresponding change with 80% power (b).

(a) Total MD change (dB)	Progression rate (dB/year)
	2 years	3 years	5 years
−1.0	−0.5	−0.3	−0.2
−2.0	−1.0	−0.7	−0.4
−4.0	−2.0	−1.3	−0.8

(b) Total MD change (dB)	Annual examinations
	2 years	3 years	5 years
−1.0	7	6	4
−2.0	5	4	3
−4.0	3	3	2