title: Nonselective loss of contrast sensitivity in visual system testing in early type I diabetes.
abstract: OBJECTIVE
  Psychophysical methods in patients with diabetes mellitus reveal deficits of central or foveal vision. Our aim was to evaluate the contrast-sensitivity thresholds in 24 insulin-dependent (type I) diabetic patients with a short disease duration and without retinopathy, taking into account metabolic control.
  
  
  METHODS
  The control group consisted of age-matched nondiabetic subjects. None had visual or systemic symptoms. Contrast sensitivity measured at eight different spatial frequencies to sinusoidal bar patterns of 0.6-12.2 cycles/deg can detect functional defects in the spatially sensitive retinal ganglion cells or in higher visual pathways. We performed two different temporal types of contrast-sensitivity testing, dynamic (8 Hz) and static (0 Hz).
  
  
  RESULTS
  Significant losses with dynamic contrast-sensitivity test at all but the highest spatial frequencies (i.e., 12.2 cycles/deg) were shown, whereas there was significant attenuation of contrast sensitivity at five spatial frequencies (1.0, 1.4, 2.2, 7.1, and 9.6 cycles/deg) in the static mode. Grating losses (less than 2SD of control means) of contrast sensitivity were found in 33.3% (dynamic) and in 72.9% (static) of eyes of diabetic patients. HbA1c values were positively correlated at variable spatial frequencies (1.0, 1.4, and 2.2 cycles/deg for dynamic test and 0.6, 1.0, 1.4, 2.2, 4.8, and 7.1 cycles/deg for static test).
  
  
  CONCLUSIONS
  Our results suggest an early, generally nonselective neuronal damage of visual pathways that occurs before the onset of clinically detectable retinopathy. The visual deficit may be related directly to the effects of diabetes; repetitive minor hypoglycemic insults may contribute more than a marked hyperglycemic condition to the mechanisms underlying physiological changes along the optic nerve.
authors.affiliation: Department of Internal Medicine, Catholic University, Rome, Italy.
authors.forename: M A
authors.initials: MA
authors.lastname: Di Leo
authors.forename: S
authors.initials: S
authors.lastname: Caputo
authors.forename: B
authors.initials: B
authors.lastname: Falsini
authors.forename: V
authors.initials: V
authors.lastname: Porciatti
authors.forename: A
authors.initials: A
authors.lastname: Minnella
authors.forename: A V
authors.initials: AV
authors.lastname: Greco
authors.forename: G
authors.initials: G
authors.lastname: Ghirlanda
mesh_terms: D000328:Adult; D015350:Contrast Sensitivity; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D005451:Fluorescein Angiography; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D008297:Male; D012016:Reference Values
chemical_list: D006442:Glycated Hemoglobin