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E. Lakhani, T. Wright, S. Boyd, W. C. Lam, C. Westall; Functional Neuro-Retinal Changes in Adolescents with Type 1 Diabetes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5312.
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To investigate the effects of diabetes on retinal function. Specific aims: 1) To detect retinal changes associated with type 1 diabetes (T1D) in adolescents with no signs of diabetic retinopathy (DR) using electrophysiology. 2) To determine if hemoglobin A1c (HbA1c) levels correlate with the functional responses.
Cross-sectional, prospective study. Localized retinal function was assessed in patients with T1D for at least 5 years and healthy controls using standard (mfERG) and slow-flash multifocal electroretinography (sf-mfERG). Patients’ blood sugar levels were assessed and maintained within 4 to 10 mmol/L during testing. Stereoscopic fundus photographs were taken for all patients to determine absence or presence of DR. Amplitude and implicit time (IT) of dominant peaks of mfERG (103 hexagons) and sf-mfERG (61 hexagons) waveforms were measured. Z-scores determined mean number of abnormal hexagons for amplitude and IT. A subset of subjects underwent short-wavelength ERG (sERG), which preferentially stimulates short-wavelength (S) cones. Amplitude and IT of the b-wave were measured. Responses were correlated with HbA1c levels.
50 patients (16 ±2 years old) and 34 age-matched controls participated. mfERG showed no significant difference between the two groups in the mean number of abnormal hexagons for IT or amplitude. sf-mfERGs showed a difference in the mean number of abnormal hexagons for IT (controls 1.7 ±1.4, patients 2.8 ±2.2, p<0.01), but not amplitude. Seven controls and 12 patients underwent sERG. Mean IT for sERG b-wave was delayed in patients compared to controls (controls 41.1 ±3.8 ms, patients 45.9 ±3.7 ms, p<0.05) but there was no difference in amplitude. Patient HbA1c levels (range 6.5% to 13.4%,median 8.6) significantly correlated only with the mean number of abnormal hexagons for mfERG ITs (r = 0.5, p<0.01).
Preliminary sf-mfERG and sERG results indicate functional changes in inner retinal neurons and S cones in adolescents with T1D and no detectable DR. In the presence of normal serum glucose levels, glucose control over 4 to 12 weeks before testing can influence outer and middle retinal function.
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