Insulin and risk of diabetic retinopathy in patients with type 2 diabetes mellitus: data from a meta-analysis of seven cohort studies

Table 2 Quality assessment of included studies ¹

Author		Quality assessment criteria
		Selection	Comparability	Outcome	Overall quality
Gunnlaugsdottir E	2012	**	**	**	6
Geir Bertelsen	2012	**	**	**	6
Schweitzer K	2009	***	**	***	8
Romero-Aroca P	2007	**	**	***	7
Hove MN	2004	***	**	**	7
Henricsson M	1996	**	**	**	6
Deng Y	2014	***	**	***	8

¹the Newcastle-Ottawa Scale (NOS) was obtained to assess the methodological quality of the included studies.
**Two points; ***Three points.

ISSN: 1746-1596