Table 2.

Clinical manifestations of diabetes mellitus in ocular tissues.

Disease stage	Ocular tissue
	Cornea	Nerve	Retina
Early/prediabetes	Ocular lens α-crystallin formation [60]; increased central corneal thickness [61]	Decreased corneal nerve fiber length [62]	Microaneurysms; exudate; tortuosity of vessels; edema
Midpoint	Reduced corneal subbasal nerve density; increased corneal sensitivity; corneal erosion syndrome [63]	Reduced subfoveal choroidal thickness [64]; reduced corneal nerve density [65]	Macula edema; hemorrhage; retinal detachment
Late-stage diabetes	Reduced tear meniscus parameters [66]; lower nerve fiber and branch length [67]	Optic neuropathy	Severe hemorrhage; retinal tearing/detachment; blindness