Documenta Ophthalmologica

, Volume 126, Issue 2, pp 99–104 | Cite as

Sensitivity and specificity of the step VEP in suspected functional visual acuity loss

  • Ruth Hamilton
  • Michael S. Bradnam
  • Gordon N. Dutton
  • Anna L. Lai Chooi Yan
  • Tim E. Lavy
  • I. Livingstone
  • Alison M. Mackay
  • Jane R. Mackinnon
Original Research Article



Early and accurate diagnosis of functional visual loss (FVL) allows optimum management. Visual evoked potentials (VEPs) offer a means of objectively estimating acuity and therefore could assist with early and accurate diagnosis. The aim of this study was to assess the sensitivity and specificity of the step VEP in diagnosing FVL.


A retrospective audit was conducted in 36 school-aged children presenting with reduced visual acuity and clinical suspicion of FVL. All had undergone step VEP testing as part of their investigation. Medical notes were reviewed, and where necessary, referring centres, general practitioners or electronic clinical portals were consulted to obtain longer-term outcome data.


Twenty-seven of the 36 patients (75 %) were classified as having had FVL: all had a normal step VEP spatial threshold. Nine patients (25 %) had an organic cause for their acuity loss, of whom seven had abnormal step VEP spatial thresholds: the other two patients had some functional overlay to their organic disease. The step VEP sensitivity was 78 % (95 % confidence interval 40–96 %), and specificity was 100 % (95 % confidence interval 84–100 %).


The high specificity of the step VEP for FVL warrants increased suspicion of an organic cause should the step VEP spatial threshold be abnormal.


Visual evoked potentials Visual acuity Conversion disorder Functional visual loss 



The authors thank the following for providing some of the patients described in this series: Dr. A Brown, Dr. J Dudgeon, Dr. R Bowman, Dr. S Gupta, Dr. I Hanna, Dr. I Hunter, Dr. N Kennedy, Dr. J Kerr, Dr. D Mansfield and Dr. M O’Regan.

Conflict of interests



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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Ruth Hamilton
    • 1
    • 2
  • Michael S. Bradnam
    • 1
    • 2
  • Gordon N. Dutton
    • 3
  • Anna L. Lai Chooi Yan
    • 4
  • Tim E. Lavy
    • 3
  • I. Livingstone
    • 3
  • Alison M. Mackay
    • 5
  • Jane R. Mackinnon
    • 3
  1. 1.Department of Clinical Physics and Bio-engineeringRoyal Hospital for Sick ChildrenGlasgowUK
  2. 2.Department of Clinical PhysicsUniversity of GlasgowGlasgowUK
  3. 3.Department of OphthalmologyRoyal Hospital for Sick ChildrenGlasgowUK
  4. 4.School of Medicine, College of Medical, Veterinary and Life SciencesUniversity of GlasgowGlasgowUK
  5. 5.Medical PhysicsSt James University HospitalLeedsUK

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