title: Association between multifocal ERG implicit time delays and adaptation in patients with diabetes.
abstract: OBJECTIVE
  Local first-order multifocal electroretinogram (mfERG) implicit time (K1-IT) delays have proved to be important and predictive indicators of retinal function in diabetes. To better understand the nature of these delays, the authors examined the spatial association between K1-IT and second-order amplitudes (K2-SNR; a measure of adaptation) in diabetic and control subjects.
  
  
  METHODS
  The authors studied K1-IT, K1 amplitude, and K2-SNRs of responses from 35 retinal zones. These were recorded from 20 diabetic patients without retinopathy, 20 patients with mild to moderate nonproliferative diabetic retinopathy (NPDR), and 30 healthy control subjects. The K1-IT and K2-SNR measurements were then adjusted according to normative and subject median values to reduce or remove the effects of retinal location, intersubject differences, and abnormally small K1 amplitudes.
  
  
  RESULTS
  There was no significant association between K1-IT and K2-SNR in the control group (P > 0.05) and only a marginal association in the NoRet group (P = 0.05). In contrast, longer K1-ITs were significantly associated with reduced K2-SNRs in NPDR subjects (P < 0.01). In the NPDR eyes, zones without retinopathic lesions showed a significant association between K1-IT and K2-SNR (P < 0.01).
  
  
  CONCLUSIONS
  The results suggest that an association between longer K1-IT and reduced K2-SNR (abnormal adaptation) develops after the appearance of NPDR, but this association does not depend on the presence of colocalized retinopathic lesions.
authors.affiliation: Vision Science Program, School of Optometry, University of California at Berkeley, Berkeley, CA 94720-2020, USA. kbc@berkeley.edu
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Bronson-Castain
authors.forename: Marcus A
authors.initials: MA
authors.lastname: Bearse
authors.forename: Ying
authors.initials: Y
authors.lastname: Han
authors.forename: Marilyn E
authors.initials: ME
authors.lastname: Schneck
authors.forename: Shirin
authors.initials: S
authors.lastname: Barez
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Adams
mesh_terms: D000328:Adult; D003922:Diabetes Mellitus, Type 1 / Q000150:complications; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D003930:Diabetic Retinopathy / Q000209:etiology / Q000503:physiopathology*; D004596:Electroretinography; D006801:Humans; D008875:Middle Aged; D012160:Retina / Q000503:physiopathology*; D013997:Time Factors