Table 2

Estimated time of origin of vision impairment by birthweight group

Birth weight (g)		Time of origin of impairment
		Prenatal				Perinatal				Postnatal				Not known				Total
		No	%			No	%			No	%			No	%			No	%
<1500	8	27.6		18	62.1		2	6.9		1	3.4		29	100.0
1500–2499	20	74.1		5	18.5		2	7.4		0	0		27	100.0
2500–3499	49	62.8		13	16.7		10	12.8		6	7.7		78	100.0
>3500	23	71.9		4	12.5		3	9.4		2	6.3		32	100.0
All weights	100	60.3		40	24.1		17	10.2		9	5.4		166	100.0