Table 2.

Studies that report no structural changes in the outer retina in diabetes.

Species	Strain	Duration of diabetes	Type of Diabetes	Photoreceptor abnormality	RPE abnormality	Reference
Rats	Sprague-Dawley	12 weeks	Streptozotocin (Type I diabetes)	No apoptosis in ONL	-	(Enzsoly et al., 2014)
Rats	Sprague-Dawley	4–5 weeks	TetO rats (Type II diabetes)	No change in ONL nuclear density	-	(Reichhart et al., 2017)
Mice	C57BL/6J	6 weeks	Streptozotocin (Type I diabetes)	No change in ONL cell number	-	(Moore-Dotson et al., 2016)
Mice	C57BL/6J	2–14 weeks	Alloxan (Type I diabetes)	No apoptosis or reduction in thickness of the outer retina	-	(Martin et al., 2004)
Mice	C57BL/6J	15–90 days	Alloxan (Type I diabetes)	No apoptosis or reduced thickness in the outer retina	-	(Gaucher et al., 2007)
Mice	C57BL/6J	3–9 months	Ins2Akita (Type I diabetes)	No rod photoreceptor loss	-	(Hombrebueno et al., 2014)
Mice	C57BL/6J	8 months	Streptozotocin (Type I diabetes)	No change in ONL thickness; no ONL cell loss	-	(Liu et al., 2016)
Mice	C57BL/6J	8 months	Streptozotocin (Type I)	No change in ONL thickness; no ONL cell loss	-	(Tonade et al., 2017)
Canine (Dogs)	Beagle	5 years	Alloxan (Type I diabetes)	No change in ONL, IS/OS thickness	-	(Tonade and Kern, 2017)
Human		Unspecified	Unspecified	ONL thickness increased in no DR diabetics; no change in NPDR	-	(Wanek et al., 2016)
Human	-	≥ 5 years	Type I diabetes	No change in cone density	-	(Tan et al., 2015)
Human	-	Unspecified	Unspecified	No reduction in ONL thickness	-	(Wanek et al., 2016)
Human	-	5–10 years or more	Type II diabetes	No change in photoreceptor ONL	No reduction in RPE thickness	(Tavares Ferreira et al., 2016)
Human	-	9–15 years	-	No change in ONL	-	(Gerhardinger et al., 1998)

Key:OS, Outer Segment; IS, Inner Segment; ONL, Outer Nuclear Layer; RPE, Retinal Pigment Epithelium