Documenta Ophthalmologica

, Volume 128, Issue 3, pp 191–200 | Cite as

Visual evoked potential-based acuity assessment: overestimation in amblyopia

  • Yaroslava Wenner
  • Sven P. Heinrich
  • Christina Beisse
  • Antje Fuchs
  • Michael Bach
Original Research Article

Abstract

Background/Aims

When visual acuity (VA) is assessed with spatially repetitive stimuli (e.g., gratings) in amblyopes, VA can be markedly overestimated. We evaluated to what extent this also applies to VEP-based objective acuity assessment, which typically uses gratings or checkerboards.

Methods

Seventeen subjects with amblyopia (anisometropic and strabismic) participated in the study; decimal VA range of their amblyopic eye covered 0.03–1.0 (1.5–0.0 logMAR). Using the Freiburg Acuity VEP (FrAVEP) method, checkerboard stimuli with six check sizes covering 0.02°–0.4° were presented in brief-onset mode (40 ms on, 93 ms off) at 7.5 Hz. All VEPs were recorded with a Laplacian montage. Fourier analysis yielded the amplitude and significance at the stimulus frequency. Psychophysical VA was assessed with the Landolt-C-based automated Freiburg Visual Acuity Test (FrACT).

Results

Test–retest limits of agreement for both FrACT and FrAVEP were ±0.20 logMAR. In all but two dominant eyes and high-acuity amblyopic eyes (VA <0.3 logMAR), FrACT and FrAVEP agreed within the expected limits of ±0.3 logMAR. However, the VEP-based acuity procedure overestimated single Landolt-C acuity by more than 0.3 logMAR in 9 of 17 (53 %) of the amblyopic eyes, up to 1 logMAR. While all subjects had a psychophysical acuity difference >0.2 logMAR between the dominant and amblyopic eye, only three of them showed such difference with the FrAVEP.

Conclusion

Both measurements of visual acuity with the VEP and FrACT were highly reproducible. However, as expected, in amblyopia, acuity can be markedly overestimated using the VEP. We attribute this to the use of repetitive stimulus patterns (checkerboards), which also lead to overestimation in psychophysical measures. The VEP-based objective assessment never underestimated visual acuity, but needs to be interpreted with appropriate caution in amblyopia.

Keywords

Visual acuity Objective assessment Visual evoked potentials Amblyopia 

References

  1. 1.
    Katsumi O, Denno S, Arai M, De Lopes Faria J, Hirose T (1997) Comparison of preferential looking acuity and pattern reversal visual evoked response acuity in pediatric patients. Graefes Arch Clin Exp Ophthalmol 235:684–690PubMedCrossRefGoogle Scholar
  2. 2.
    Norcia A, Tyler C (1985) Spatial frequency sweep VEP: visual acuity during the first year of life. Vis Res 25:1399–1408PubMedCrossRefGoogle Scholar
  3. 3.
    Ghasia F, Brunstom J, Tychsen L (2009) Visual acuity and visually evoked responses in children with cerebral palsy: gross motor function classification scale. Br J Ophthalmol 93:1068–1072Google Scholar
  4. 4.
    Strasburger H, Remky A, Murray IJ, Hadjizenonos C, Rentschler I (1996) Objective measurement of contrast sensitivity and visual acuity with the steady-state visual evoked potential. Ger J Ophthalmol 5:42–52PubMedGoogle Scholar
  5. 5.
    Bach M, Maurer JP, Wolf ME (2008) Visual evoked potential-based acuity assessment in normal vision, artificially degraded vision, and in patients. Br J Ophthalmol 92:396–403PubMedCrossRefGoogle Scholar
  6. 6.
    Ridder WH 3rd (2004) Methods of visual acuity determination with the spatial frequency sweep visual evoked potential. Doc Ophthalmol 109:239–247PubMedCrossRefGoogle Scholar
  7. 7.
    Mackay AM, Bradnam MS, Hamilton R, Elliot AT, Dutton GN (2008) Real-time rapid acuity assessment using VEPs: development and validation of the step VEP technique. Invest Ophthalmol Vis Sci 49:438–441PubMedCrossRefGoogle Scholar
  8. 8.
    Regan D (1978) Assessment of visual acuity by evoked potential recording: ambiguity caused by temporal dependence of spatial frequency selectivity. Vis Res 18:439–443PubMedCrossRefGoogle Scholar
  9. 9.
    Norcia AM, Tyler CW, Hamer RD, Wesemann W (1989) Measurement of spatial contrast sensitivity with the swept contrast VEP. Vis Res 29:627–637PubMedCrossRefGoogle Scholar
  10. 10.
    Meigen T, Bach M (1999) On the statistical significance of electrophysiological steady-state responses. Doc Ophthalmol 98:207–232PubMedCrossRefGoogle Scholar
  11. 11.
    McBain VA, Robson AG, Hogg CR, Holder GE (2007) Assessment of patients with suspected non-organic visual loss using pattern appearance visual evoked potentials. Graefes Arch Clin Exp Ophthalmol 245:502–510PubMedCrossRefGoogle Scholar
  12. 12.
    Harter MR, White CT (1970) Evoked cortical responses to checkerboard patterns: effect of check-size as a function of visual acuity. Electroencephalogr Clin Neurophysiol 28:48–54PubMedCrossRefGoogle Scholar
  13. 13.
    Tyler CW, Apkarian P, Levi DM, Nakayama K (1979) Rapid assessment of visual function: an electronic sweep technique for the pattern visual evoked potential. Invest Ophthalmol Vis Sci 18:703–713PubMedGoogle Scholar
  14. 14.
    Apkarian PA, Nakayama K, Tyler CW (1981) Binocularity in the human visual evoked potential: facilitation, summation and suppression. Electroencephalogr Clin Neurophysiol 51:32–48PubMedCrossRefGoogle Scholar
  15. 15.
    Strasburger H, Rentschler I, Scheidler W (1986) Steady-state pattern VEP uncorrelated with suprathreshold contrast perception. Hum Neurobiol 5:209–211PubMedGoogle Scholar
  16. 16.
    Bach M, Joost W (1989) VEP vs spatial frequency at high contrast: subjects have either a bimodal or single-peaked response function. In: Kulikowski J, Dickinson C, Murray I (eds) Seeing contour colour. Pergamon Press, Oxford, pp 478–484Google Scholar
  17. 17.
    Parry NR, Murray IJ, Hadjizenonos C (1999) Spatio-temporal tuning of VEPs: effect of mode of stimulation. Vis Res 39:3491–3497PubMedCrossRefGoogle Scholar
  18. 18.
    Heinrich SP (2010) Some thoughts on the interpretation of steady-state evoked potentials. Doc Ophthalmol 120:205–214PubMedCrossRefGoogle Scholar
  19. 19.
    Friendly DS, Jaafar MS, Morillo DL (1990) A comparative study of grating and recognition visual acuity testing in children with anisometropic amblyopia without strabismus. Am J Ophthalmol 110:293–299PubMedGoogle Scholar
  20. 20.
    Bach M, Strahl P, Waltenspiel S, Kommerell G (1990) Amblyopia: reading speed in comparison with visual acuity for gratings, single Landolt Cs and series Landolt Cs. Fortschr Ophthalmol 87:500–503Google Scholar
  21. 21.
    Gwiazda JE (1992) Detection of amblyopia and development of binocular vision in infants and children. Curr Opin Ophthalmol 3:735–740PubMedCrossRefGoogle Scholar
  22. 22.
    Kushner BJ, Lucchese NJ, Morton GV (1995) Grating visual acuity with Teller cards compared with Snellen visual acuity in literate patients. Arch Ophthalmol 113:485–493PubMedCrossRefGoogle Scholar
  23. 23.
    Stuart JA, Burian HM (1962) A study of separation difficulty. Its relationship to visual acuity in normal and amblyopic eyes. Am J Ophthalmol 53:471–477PubMedGoogle Scholar
  24. 24.
    Chen SI, Norcia AM, Pettet MW, Chandna A (2005) Measurement of position acuity in strabismus and amblyopia: specificity of the vernier VEP paradigm. Invest Ophthalmol Vis Sci 46:4563–4570PubMedCrossRefGoogle Scholar
  25. 25.
    Ridder WH, Rouse MW (2007) Predicting potential acuities in amblyopes: predicting post-therapy acuity in amblyopes. Doc Ophthalmol 114:135–145PubMedCrossRefGoogle Scholar
  26. 26.
    World Medical Association (2000) Declaration of Helsinki: ethical principles for medical research involving human subjects. J Am Med Assoc 284:3043–3045CrossRefGoogle Scholar
  27. 27.
    Bach M (1996) The Freiburg Visual Acuity Test: automatic measurement of visual acuity. Optom Vis Sci 73:49–53Google Scholar
  28. 28.
    Bach M, Dakin SC (2009) Regarding “Eagle-eyed visual acuity: an experimental investigation of enhanced perception in autism”. Biol Psychiatry 66:e19–e20 author reply e23–24PubMedCrossRefGoogle Scholar
  29. 29.
    Tavassoli T, Latham K, Bach M, Dakin SC, Baron-Cohen S (2011) Psychophysical measures of visual acuity in autism spectrum conditions. Vis Res 51:1778–1780PubMedCrossRefGoogle Scholar
  30. 30.
    Loumann Knudsen L (2003) Visual acuity testing in diabetic subjects: the decimal progression chart versus the Freiburg Visual Acuity Test. Graefes Arch Clin Exp Ophthalmol 241:615–618Google Scholar
  31. 31.
    Wesemann W (2002) Visual acuity measured via the Freiburg Visual Acuity Test (FVT), Bailey Lovie chart and Landolt Ring chart. Klin Monbl Augenheilkd 219:660–667Google Scholar
  32. 32.
    Schulze-Bonsel K, Feltgen N, Burau H, Hansen L, Bach M (2006) Visual acuities “hand motion” and “counting fingers” can be quantified with the Freiburg visual acuity test. Invest Ophthalmol Vis Sci 47:1236–1240PubMedCrossRefGoogle Scholar
  33. 33.
    Lieberman HR, Pentland AP (1982) Microcomputer-based estimation of psychophysical thresholds: the best PEST. Behav Res Method Instrum 14:21–25CrossRefGoogle Scholar
  34. 34.
    Treutwein B (1995) Adaptive psychophysical procedures. Vis Res 35:2503–2522PubMedCrossRefGoogle Scholar
  35. 35.
    Bach M (2007) Freiburg evoked potentials. http://www.michaelbach.de/ep2000.html. Accessed 19 Aug 2013
  36. 36.
    Mackay A, Bradnam M, Hamilton R (2003) Rapid detection of threshold VEPs. Clin Neurophysiol 114:1009–1020PubMedCrossRefGoogle Scholar
  37. 37.
    Fahle M, Bach M (2006) Basics of the VEP. In: Heckenlively J, Arden G (eds) Principles and practice of clinical electrophysiology of vision. MIT Press, Cambridge, pp 207–234Google Scholar
  38. 38.
    Bach M, Meigen T (1999) Do’s and don’ts in Fourier analysis of steady-state potentials. Doc Ophthalmol 99:69–82PubMedCrossRefGoogle Scholar
  39. 39.
    Zhou P, Zhao MW, Li XX, Hu XF, Wu X, Niu LJ, Yu WZ, Xu XL (2008) A new method of extrapolating the sweep pattern visual evoked potential acuity. Doc Ophthalmol 117:85–91PubMedCrossRefGoogle Scholar
  40. 40.
    R Development Core Team (2006) R: a language and environment for statistical computing. http://www.R-project.org. Accessed 26 Oct 2013
  41. 41.
    Bland JM, Altman DG (1999) Measuring agreement in method comparison studies. Stat Methods Med Res 8:135–160PubMedCrossRefGoogle Scholar
  42. 42.
    Bach M (2007) The Freiburg visual acuity test: variability unchanged by post hoc re-analysis. Graefes Arch Clin Exp Ophthalmol 245:965–971PubMedCrossRefGoogle Scholar
  43. 43.
    Holopigian K, Bach M (2010) A primer on common statistical errors in clinical ophthalmology. Doc Ophthalmol 121:215–222PubMedCrossRefGoogle Scholar
  44. 44.
    Haase W, Hohmann A (1982) A new test (C-test) for quantitative examination of crowding with test results in amblyopic and ametropic patients (author’s transl). Klin Monatsblätter Für Augenheilkd 180:210–215CrossRefGoogle Scholar
  45. 45.
    Gräf MH, Becker R, Kaufmann H (2000) Lea symbols: visual acuity assessment and detection of amblyopia. Graefes Arch Clin Exp Ophthalmol 238:53–58PubMedCrossRefGoogle Scholar
  46. 46.
    Mayer DL (1986) Acuity of amblyopic children for small field gratings and recognition stimuli. Invest Ophthalmol Vis Sci 27:1148–1153PubMedGoogle Scholar
  47. 47.
    Katz B, Sireteanu R (1989) The Teller acuity card test: possibilities and limits of clinical use. Klin Monatsbl Augenheilkd 195:17–22PubMedCrossRefGoogle Scholar
  48. 48.
    Gräf M, Dietrich H (1994) Objective vernier acuity testing in adults, children and infants. Possibilities and limits of a new method. Klin Monatsblätter Für Augenheilkd 204:98–104CrossRefGoogle Scholar
  49. 49.
    Hess RF, Campbell FW, Greenhalgh T (1978) On the nature of the neural abnormality in human amblyopia; neural aberrations and neural sensitivity loss. Pflüg Arch 377:201–207CrossRefGoogle Scholar
  50. 50.
    Gräf M (1998) Objective assessment of minimum visual acuity by suppression of optokinetic nystagmus. Klin Monatsblätter Für Augenheilkd 212:196–202CrossRefGoogle Scholar
  51. 51.
    Graf MH (1999) Information from false statements concerning visual acuity and visual field in cases of psychogenic visual impairment. Graefes Arch Clin Exp Ophthalmol 237:16–20PubMedCrossRefGoogle Scholar
  52. 52.
    Heinrich SP, Marhöfer D, Bach M (2010) “Cognitive” visual acuity estimation based on the event-related potential P300 component. Clin Neurophysiol 121:1464–1472Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Yaroslava Wenner
    • 1
  • Sven P. Heinrich
    • 2
  • Christina Beisse
    • 3
  • Antje Fuchs
    • 2
  • Michael Bach
    • 2
  1. 1.Department of OphthalmologyPhillips-University Marburg, Universitätsklinikum Giessen & Marburg GmbHMarburgGermany
  2. 2.Eye CenterUniversity of FreiburgFreiburgGermany
  3. 3.University Eye HospitalHeidelbergGermany

Personalised recommendations