A New Model for Assessment of Change in Visual Function in Diabetes

Sammanfattning: The purpose of this thesis was to determine whether perimetry using a new model to interpret deterioration or improvement in the visual field can be employed to assess change in visual function over time in diabetes. Diabetic retinopathy has long been considered a microvascular disease, but it is still a matter of debate to what extent diabetes also affects retinal neurons. Visual acuity is routinely tested to evaluate visual function in diabetes, but can vary for no obvious reasons and even be normal despite severe vessel abnormalities, and hence less useful for early detection of visual impairment. Until now, no measure has proven to be suitable for identifying early changes in retinal function in diabetes. Two cohorts were investigated. The first cohort comprised 55 diabetic patients with various degrees of diabetic retinopathy. Using a cross-sectional design, we studied how refraction and visual acuity varied in patients under routine care (Study I), and we assessed limits for significant change in visual fields by use of standard automated perimetry (SAP) and short-wavelength automated perimetry (SWAP) based on short-term test–retest variability (Study II). The second cohort consisted of 81 diabetic subjects with no or mild/moderate diabetic retinopathy. We applied a longitudinal prospective design to explore the correlation between functional change and progression of microvascular abnormalities (Study III), and examined the usefulness of SAP with our limits of significant change for detecting early retinal dysfunction over 3–5 years (Study IV). In Study I, we demonstrated that refraction was stable in most eyes, and assessments of visual acuity were highly reproducible despite substantial fluctuations in blood glucose levels. In Study II, we defined limits of significant change for SAP and SWAP for diabetic subjects. In Study III, we used the defined limits for change to monitor visual function in diabetes by SAP. After 18 months of follow-up, deterioration was common but improvement was rare, and deteriorated fields were reproducible despite an unchanged degree of retinopathy. In Study IV, up to five years of follow-up, confirmed visual field deterioration in eyes without any retinopathy or with stable mild/moderate retinopathy. Standard automated perimetry with our new model for detecting change can successfully determine early retinal dysfunction over time in diabetes, which can represent early signs and progression of retinal neurodegeneration.