Barbara King-Hooper

Adolescents with Type 2 Diabetes: Early Indications of Focal Retinal Neuropathy, Retinal Thinning and Venular Dilation

Purpose: The eye provides a unique window into the neural and vascular health of a patient with diabetes. The present study is the first of its kind to examine the neural retinal function, structure, and retinal vascular health in adolescents with Type 2 diabetes. Methods: Focal neural responses from 103 discrete retinal regions of the eye were tested using multifocal electroretinography. Optical coherence tomography was utilized to measure retinal thickness. Digital fundus photographs were examined for the presence of retinopathy and to measure vascular caliber using retinal vessel analysis. Fifteen adolescents diagnosed with Type 2 diabetes, aged 13 to 21 years with a mean diabetes duration of 2.1 ± 1.3 years, were tested. Twenty-six age-matched control subjects were also tested. Results: Multifocal electroretinograms of the Type 2 diabetic group were significantly (P = 0.03) delayed by 0.49 milliseconds. The diabetic group also showed significant (both; P ≤ 0.03) retinal thinning (10.3 &mgr;m) and significant venular dilation (16.2 &mgr;m). Conclusion: The present study shows early indications of focal retinal neuropathy, retinal thinning, and venular dilation in adolescents with Type 2 diabetes. Early detection of functional and structural changes will hopefully aid in the prevention of permanent damage or further functional loss.

Early neural and vascular changes in the adolescent type 1 and type 2 diabetic retina.

Purpose: This cross-sectional study examines the existence and frequency of functional and structural abnormalities in the adolescent Type 1 diabetic retina. We also compare the results with those of adolescents with Type 2 diabetes. Methods: Thirty-two adolescents with Type 1 diabetes (5.7 ± 3.6 years; mean duration ± SD), 15 with Type 2 diabetes (2.1 ± 1.3 years), and 26 age-matched control subjects were examined. Multifocal electroretinogram responses from 103 retinal regions were recorded. Optical coherence tomography was used to measure retinal thickness. Vascular diameter around the optic nerve was also assessed. Results: Nine of the 32 (28%) adolescents with Type 1 diabetes and 6 of the 15 (40%) with Type 2 diabetes had significant multifocal electroretinogram implicit time delays compared with 2 of the 26 controls (8%). Retinal thicknesses in both patient groups were significantly (P ≤ 0.01) thinner than controls. The Type 2 group also showed significant (P ≤ 0.03) retinal venular dilation (235.8 ± 5.9 μm) compared with controls (219.6 ± 4.0 μm). Conclusion: The present study illustrates that subtle but significant functional and structural changes occur very early in Type 1 diabetes. Adolescents with Type 2 diabetes appear to be more affected than those with Type 1 diabetes. Further longitudinal examination of the etiology and progression of these abnormalities is warranted.

Interocular Symmetry of Abnormal Multifocal Electroretinograms in Adolescents with Diabetes and No Retinopathy

PURPOSE To investigate, in adolescents with type 1 diabetes and no retinopathy, the spatial correspondence between abnormal multifocal electroretinogram (mfERG) responses in the two eyes. METHODS mfERG and fundus photographs were measured in both eyes of 68 adolescents with type 1 diabetes and no retinopathy (13 to 19 years old; best corrected visual acuity ≥ 20/20), and 30 age-matched controls. The mfERG stimulus was comprised of 103 hexagons, and subtended 45°. mfERG implicit times (IT) and amplitudes (AMP) were derived. Fifteen patients for IT, and five for AMP with at least one eye defined as abnormal (six or more locations with abnormal Z-scores; P < 0.03) were analyzed. RESULTS Nasal retina had significantly more abnormal IT locations compared with temporal retina (P = 0.015), and the opposite was true with regard to abnormal AMP (P < 0.001). The proportion of abnormal responses in the superior retina was not significantly different from that in the inferior retina (P > 0.1 for IT and AMP). Interocular correspondence of locations with abnormal mfERG IT was significant for all 15 patients (P values <0.0001-0.012), and agreement between eyes was 68% to 94% (AC1 agreement coefficient: 0.48-0.94). Overall interocular correspondence was also significant (P < 0.0002), with 86% agreement (AC1 = 0.76). Overall interocular correspondence of locations with abnormal mfERG AMP was also significant (P < 0.0002). CONCLUSIONS Interocular spatial correspondence of abnormal mfERG responses exists in adolescents with type 1 diabetes and no retinopathy. This is most apparent for IT abnormalities. This correspondence could be used in clinical trials, and raises the possibility of initiating treatment in both eyes at early disease stages as new topical treatments emerge.

Association between local neuroretinal function and control of adolescent type 1 diabetes.

PURPOSE To evaluate associations between neuroretinal function measured with multifocal electroretinogram (mfERG) and disease variables in adolescents with type 1 diabetes and no retinopathy. METHODS Fundus photographs, blood glucose (BG) concentration, HbA1c, and monocular mfERG were performed on 115 adolescent patients (mean age ± SD; 15.7 ± 1.8 years) and 30 controls (18.0 ± 2.8 years). All subjects had best-corrected visual acuity ≥ 20/20. The 45° mfERG stimulus included 103 hexagons, reversing between dark and bright according to a pseudorandom m-sequence. Amplitudes (AMPs) and implicit times (ITs) were derived from local mfERG response waveforms, and Z-scores were calculated. Retinal maps of abnormality frequencies were generated. Differences between controls and patients were evaluated using t-tests. Associations between mfERG and age, duration, and diabetes control were examined using linear regression analysis. RESULTS Mean mfERG IT was significantly longer in the patients compared with that in the controls (P = 0.019), but AMP was not different (P > 0.05). In all, 26 eyes (23%) of the patients had abnormal IT and 3 eyes (3%) had abnormal AMP. IT abnormalities were essentially distributed randomly across the retina. There were too few AMP abnormalities to examine their retinal distribution. IT was positively correlated with HbA1c (P < 0.0002) but not correlated with diabetes duration, BG, or age. CONCLUSIONS Higher long-term blood glucose concentration is associated with degraded neuroretinal function in adolescents with type 1 diabetes and no retinopathy. Over 20% of these patients have abnormal neuroretinal function. It will be important to determine longitudinally whether the relationship between mfERG IT and diabetes control exists within individual adolescent patients.