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M. T. McFarlane, G. Mirabella, T. Wright, E. Lakhani, C. Westall; Investigating the Retinal Contribution to Short-Wavelength Colour Defect in Adolescents With Type I Diabetes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5313.
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To determine if short-wavelength sensitivity loss found previously in adolescents with Type I Diabetes (T1D) and no evidence of diabetic retinopathy (Elia et al., IOVS 2005) is associated with a retinal defect at the level of the short-wavelength sensitive (S) cone pathways.
Electrophysiological testing was performed in a cross-sectional, prospective study on 6 subjects (15 ± 1.76 years old) who had T1D for at least 5 years and 5 control subjects (19 ± 4.55 years old). All subjects underwent ophthalmological examination. Ambient blood glucose was monitored and maintained between 4-10mmol/L before and during testing. Short-wavelength electroretinograms (sERGs) were recorded using short-wavelength flashes (peak at 410nm) against an amber (594 nm) background. The primary outcome measure was implicit time of the b-wave. Chromatic visual evoked potentials (cVEPs) were recorded using the International 10/20 System of Electrode Placement. Short-wavelength (S), and long- and medium-wavelength (LM) colour stimuli consisted of vertical, photometric isoluminant sinusoidal gratings (1cyc/deg) at 20% colour contrast and were presented in a pattern onset (100ms)-offset (400ms) mode at 2Hz. The primary outcome measure was cVEP latency.
sERG implicit times were significantly delayed in adolescents with T1D in comparison to controls (p=0.003). In the same subjects, cVEP latencies to blue-yellow (tritan) stimuli were delayed in those with T1D in comparison to controls (p=0.007).
S-cone visual pathways are selectively affected in adolescent subjects with T1D. sERG results indicate retinal dysfunction in the S-cone retinal pathways in adolescents with T1D. cVEP results indicate a defect in the short-wavelength pathway leading from the retina to the visual cortex in subjects with T1D. The cVEP deficit may be partially explained by S-cone deficit.
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