title: Does neuronal damage precede vascular damage in subjects with type 2 diabetes mellitus and having no clinical diabetic retinopathy?
abstract: OBJECTIVE
  To investigate the occurrence of neuronal damage, as the earliest change occurring, before the clinical evidence of diabetic retinopathy.
  
  
  METHODS
  70 eyes of subjects with type 2 diabetes mellitus and with no evidence of diabetic retinopathy (cases) and 40 eyes of subjects with no diabetes mellitus (controls) were studied using spectral-domain OCT and microperimetry. The influence of age and gender on the outcome measures was also analyzed.
  
  
  RESULTS
  Age- and gender-matched subjects showed a decreased mean retinal nerve fiber layer thickness in cases when compared to the controls (27 vs. 33 μm; p=0.018). Among the cases, subjects between 40 and 45 years of age showed a reduced mean central foveal thickness (175.1 vs. 198.1 μm; p=0.05), mean retinal thickness in the central 6-mm fundus (260.5 vs. 275.3 μm; p=0.006) and mean retinal nerve fiber layer thickness (29 vs. 39 μm; p=0.036) when compared to the controls. However, no differences were noted in the microperimetry outcomes in cases when compared to the controls. The duration of diabetes and the glycemic control did not show any significant changes on the outcome measures in cases, except for a significantly lower mean retinal sensitivity in diabetics with glycosylated hemoglobin values<7% as compared to those with glycosylated hemoglobin≥7% (14.1±2.9 vs. 15.4±1.7 dB; p=0.027).
  
  
  CONCLUSIONS
  The results suggest that there is some evidence of early neuronal damage particularly on spectral-domain OCT, before the clinical evidence of diabetic retinopathy, in subjects with type 2 diabetes mellitus.
authors.affiliation: Shri Bhagwan Mahavir Vitreoretinal Services, Department of Preventive Ophthalmology, Elite School of Optometry, Sankara Nethralaya, Chennai, India.
authors.forename: Aditya
authors.initials: A
authors.lastname: Verma
authors.forename: Rajiv
authors.initials: R
authors.lastname: Raman
authors.forename: K
authors.initials: K
authors.lastname: Vaitheeswaran
authors.forename: Swakshyar Saumya
authors.initials: SS
authors.lastname: Pal
authors.forename: Gella
authors.initials: G
authors.lastname: Laxmi
authors.forename: Muneeswar
authors.initials: M
authors.lastname: Gupta
authors.forename: S Chandra
authors.initials: SC
authors.lastname: Shekar
authors.forename: Tarun
authors.initials: T
authors.lastname: Sharma
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis*; D003930:Diabetic Retinopathy / Q000175:diagnosis*; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009887:Ophthalmoscopy; D011446:Prospective Studies; D012165:Retinal Ganglion Cells / Q000473:pathology*; D012171:Retinal Vessels / Q000473:pathology*; D041623:Tomography, Optical Coherence; D058609:Visual Field Tests
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human