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Relationship between fasted insulin levels and mfERG implicit times in patients with type 2 diabetes and prediabetes

Jennyffer D Smith1, Rachel Redfern2, Liam Burhans2

  • 1University of Houston College of Optometry, Houston, TX, USA. jsmith41@central.uh.edu.

Documenta Ophthalmologica. Advances in Ophthalmology
|February 19, 2025
PubMed
Abstract

Insights

Reduced blood insulin is linked to delayed retinal function (P1 implicit time) in fasted individuals with type 2 diabetes (T2DM) or prediabetes. This suggests insulin deficiency may impair vision even before retinopathy develops.

Area of Science:

  • Ophthalmology
  • Endocrinology
  • Diabetology

Background:

  • Type 2 diabetes (T2DM) is known to alter multifocal electroretinography (mfERG) parameters, specifically delaying P1 implicit time (IT), even before retinopathy is evident.
  • This delay is often attributed to hyperglycemia-induced retinal cell damage.
  • However, altered insulin levels in prediabetes and T2DM patients have not been investigated for their impact on retinal function via mfERG.

Purpose of the Study:

  • To investigate the relationship between blood insulin levels and mfERG parameters in individuals with and without T2DM and prediabetes.
  • To explore whether insulin levels, independent of hyperglycemia, influence retinal function as measured by mfERG.

Main Methods:

  • A cross-sectional study included 66 subjects categorized by HbA1c into controls (<5.7%), prediabetes (5.7-6.4%), and T2DM (>6.4% or diagnosed).
  • Fasting blood glucose, fasting blood insulin (ELISA), and mfERG (103 hexagons, 4-min m-sequence) were assessed.
  • Data were analyzed using ANOVA and multivariate regression, controlling for age, T2DM duration, and blood glucose.

Main Results:

  • A significant positive correlation was found between fasting blood glucose and mfERG P1 IT across all subjects (P < 0.002).
  • After controlling for covariates, a negative relationship was observed between averaged mfERG IT and fasting blood insulin concentration (P = 0.035).
  • T2DM subjects exhibited significantly longer mfERG IT compared to controls and prediabetes (P = 0.008), but no differences were found between controls and prediabetes.

Conclusions:

  • Reduced blood insulin levels are associated with delayed mfERG P1 IT under overnight fasted conditions, suggesting that insulin deficiency may impair retinal function.
  • These findings highlight a potential role for insulin in maintaining retinal health, independent of direct hyperglycemic effects.
  • Further research is recommended to explore these associations under standardized postprandial conditions, such as during oral glucose tolerance testing.
Keywords:
DiabetesDiabetic retinopathyInsulinMultifocal electroretinography

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