Abstract
Purpose: :
To assess visual acuity (VA) outcomes and factors associated with preservation of excellent VA in patients despite ≥50 years of type 1 diabetes mellitus (DM) (Joslin Medalists).
Methods: :
Cross sectional evaluation of Medalists included ETDRS-protocol VA & fundus photography, dilated eye examination, Stratus OCT imaging, evaluation of diabetic complications, hemoglobin A1c (HbA1c), blood pressure and lipid parameters. Photos were graded by 2 masked readers for ETDRS diabetic retinopathy (DR) severity level and discrepancies were adjudicated.
Results: :
In 557 Medalists, median age was 66 [Q1, Q3: 61, 72] yrs, DM duration 53 [51, 58] yrs, current HbA1c 7.2 [6.7, 7.8] % and 51.4% were female. Median logmar VA was 0.04 (Snellen equivalent 20/20-2). In the better-seeing eye, 60.3% of Medalists had VA ≥ 20/20, 33.5% had VA < 20/20 and >= 20/40, and only 6.3% had VA < 20/40. In the worse-seeing eye, 76.1% had VA >= 20/40. VA preservation of 20/20 or better was associated with younger current age (65.0 vs 68.5 yrs, p<0.001), younger age at diagnosis (10.6 vs 12.0 yrs, p=0.01), shorter duration of DM (54.5 vs 56.5 yrs, p<0.001), and lower current HbA1c (7.2 vs 7.4%, p=0.01). In contrast, DR status was significantly associated with age but not with duration of DM or HbA1c. VA of 20/20 or better was strongly associated with the absence of diabetic vascular complications including proliferative diabetic retinopathy (p<0.001), nephropathy (p=0.004), and cardiovascular disease (p=0.003). Better VA was only modestly correlated with thinner OCT-measured central subfield thickness (r=0.08, p=0.009). Blood pressure and lipid parameters were not associated with VA outcomes.
Conclusions: :
Despite extremely long duration of DM, excellent VA is maintained in a majority of Medalists (60% with VA>=20/20, 94% >= 20/40). This unique cohort may therefore allow us to identify factors associated with visual preservation in DM. Since classic risk factors such as current glycemic control and duration of DM are related to VA but not DR severity, at least some pathophysiologic mechanisms underlying functional versus anatomic outcomes in diabetes may be distinct.
Keywords: diabetic retinopathy • diabetes • visual acuity