Table 2

Dose related risk factors (20% of the total dose

Variable	No	No	Yes	p Value	RR
% of retina
⩽35%	262	216	46	<0.0001	1
>35%	172	102	70		2.9
Volume of eye
⩽3 cm³	245	221	24	<0.0001	1
>3 cm³	189	97	92		7.09
% of ciliary body
⩽40%	250	222	28	<0.0001	1
>40%	184	96	88		6.2
% of optic disc
⩽40%	261	190	71	NS	1.08
>40%	173	128	45		1
% of macula
⩽50%	222	150	72	0.0007	1.6
>50%	212	168	44		1
Length of optic nerve
⩽1 mm	282	209	73	NS	1
>1 mm	152	109	43		1.05