Table 3. Intra- and inter-observer differences between nerve-head to fovea distance (NFD) measurements made from the center and the rim of the nerve-head in 30 right eyes (OD) and 30 left eyes (OS).

Measure	Test	Mean Square	F	P-value
Center of the nerve-head
OD	Within observer 1	0.00247	1.47	0.24
	Within observer 2	0.00210	0.94	0.40
	Between observer 1 and observer 2	0.03784	2.60	0.12
OS	Within observer 1	0.00092	0.59	0.56
	Within observer 2	0.00076	0.45	0.64
	Between observer 1 and observer 2	0.01096	0.99	0.33
Rim of the nerve-head
OD	Within observer 1	0.00163	0.99	0.38
	Within observer 2	0.00007	0.022	0.98
	Between observer 1 and observer 2	1.20324	38.40	9.3 10−7
OS	Within observer 1	0.00400	2.88	0.064
	Within observer 2	0.00001	0.004	1.00
	Between observer 1 and observer 2	0.26019	8.35	0.0072