title: Diabetes mellitus affects biomechanical properties of the optic nerve head in the rat.
abstract: BACKGROUND
  To investigate the effect of diabetes on the biomechanical behavior of the optic nerve head (ONH) and the peripapillary sclera (ppSc) in streptozocine-induced diabetic rats.
  
  
  METHODS
  Diabetes mellitus was induced in 20 Wistar rats using streptozocine. Twenty-five nondiabetic rats served as controls. Eyes were enucleated after 12 weeks and 2 strips of one eye were prepared containing ONH or ppSc. The stress-strain relation was measured in the stress range of 0.05-10 MPa using a biomaterial tester.
  
  
  RESULTS
  At 5% strain the stress of the ONH in diabetic rats was 897±295 kPa and in the control group it was 671±246 kPa; there was a significant difference between both groups (p=0.011). The stress of the diabetic ppSc (574±185 kPa) increased compared to that of the nondiabetic ppSc (477±171 kPa), but this did not reach statistical significance (p=0.174). The calculated tangent modulus at 5% strain was 11.79 MPa in the diabetic ONH and 8.77 MPa in the nondiabetic ONH; there was a significant difference between both groups (p=0.006). The calculated tangent modulus at 5% strain was 7.17 MPa in the diabetic ppSc and 6.12 MPa in the nondiabetic ppSc, without a statistically significant difference (p=0.09).
  
  
  CONCLUSIONS
  In contrast to the ppSc, the ONH of diabetic rats showed a significant increase in stiffness compared to nondiabetic rats, which might be explained by nonenzymatic collagen cross-linking mediated by advanced glycation end products due to high blood glucose levels in diabetes. Further studies are needed to investigate if these biomechanical changes represent a detrimental risk factor for intraocular pressure regulation in diabetic glaucoma patients.
authors.affiliation: Department of Ophthalmology, Carl Gustav Carus University Hospital, Dresden, Germany. naim.terai@uniklinikum-dresden.de
authors.forename: Naim
authors.initials: N
authors.lastname: Terai
authors.forename: Eberhard
authors.initials: E
authors.lastname: Spoerl
authors.forename: Michael
authors.initials: M
authors.lastname: Haustein
authors.forename: Karin
authors.initials: K
authors.lastname: Hornykewycz
authors.forename: Janek
authors.initials: J
authors.lastname: Haentzschel
authors.forename: Lutz E
authors.initials: LE
authors.lastname: Pillunat
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001786:Blood Glucose / Q000032:analysis; D003094:Collagen / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000503:physiopathology*; D055119:Elastic Modulus / Q000502:physiology*; D005901:Glaucoma / Q000503:physiopathology; D017127:Glycation End Products, Advanced / Q000378:metabolism; D008297:Male; D009898:Optic Disk / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D012590:Sclera / Q000503:physiopathology
chemical_list: D001786:Blood Glucose; D017127:Glycation End Products, Advanced; D003094:Collagen