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K. Bronson-Castain, M. A. Bearse, Jr., J. Neuville, S. Jonasdottir, B. King-Hooper, M. E. Schneck, A. J. Adams; Focal Retinal Neuropathy and Macular Thickness in Adolescents With Type 1 Diabetes. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2757.
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© ARVO (1962-2015); The Authors (2016-present)
To examine retinal function and macular thickness in adolescents with type 1 diabetes with either no ocular pathology (NoPATH) or mild ocular pathology (PATH) using the multifocal electroretinogram (mfERG) and optical coherence tomography (OCT).
The NoPATH group was composed of 30 adolescents (5.8 ± 3.7 yrs duration) with no ocular pathology in either eye. The PATH group (10.4 ± 1.4 yrs duration) included 3 diabetics with mild background retinopathy and 1 subject with mild diabetes related cataracts. The Control group was 26 age-matched subjects. mfERG and OCT measurements from a single eye were used. First order mfERGs were derived from 103 regions within the central 45 degrees of the retina. mfERG implicit times (IT) and amplitudes (AMP) were measured using a template stretching method (Hood & Li 1997). 12 radial scans, 6 mm long and centered at the fovea, were acquired using Stratus OCT 3. A map of macular thickness was created and segmented into 37 hexagonal regions that corresponded to the central 37 regions of the mfERG stimulus. A mean retinal thickness was then computed for each region.
The PATH and NoPATH groups differed in duration of diabetes (P<0.001). Both the PATH (28.0 ± 0.2ms, mean ± SEM) and NoPATH (27.5 ± 0.1ms) group mean mfERG IT were significantly (P<0.001) different from the Control group (27.1 ± 0.1ms) as well as from each other (P<0.001). The PATH group had significantly smaller mean AMP (231 ± 7 nV; P<0.02) compared to Controls (243 ± 7nV) as well as the NoPATH group (243 ± 7nV), but the NoPATH group did not differ from Controls (P = 0.92). Mean macular thickness of both the PATH (262 ± 5µm) and NoPATH groups (250 ± 5µm) did not differ (P = 0.2, P = 0.6, respectively) from Controls (254 ± 5µm). The PATH group's lack of significance is likely due to sample size (4). However, local macular thickness was positively correlated with AMP in the NoPATH group (R2 = 0.25, P<0.005) but only weakly correlated in the Control (R2 = 0.15, P = 0.05) and PATH (R2 = 0.84, P = 0.08) groups. IT and HbA1c were positively correlated in the NoPATH group (R2 = 0.22, P<0.01) but not in the PATH group (R2 = 0.88, P = 0.08).
mfERG implicit time is delayed in adolescents with type 1 diabetes. Both implicit time and amplitude appear to be more affected in patients with mild ocular pathology. The results show that focal neuropathy is present early in diabetes and increases in severity with ocular pathology and diabetes duration. The association between HbA1c and IT offers hope that tighter glycemic control might improve or prevent local retinal dysfunction.
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