Resolution acuity versus recognition acuity with Landolt-style optotypes

  • Sven P. HeinrichEmail author
  • Michael Bach



International standards define acuity as the reciprocal of the threshold gap size of a Landolt C optotype. However, the literature is inconsistent as to what type of acuity is measured with Landolt Cs. The present study addresses this question more directly than previous studies by quantifying the effect of an inherent luminance artifact in Landolt-style optotypes.


Two groups of modified optotypes were used. In the first group, each optotype had a single gap structure with the same average luminance. Between optotypes, the gap structures differed in their degree of fineness. In the second group of optotypes, a standard gap was always present, defining the orientation of the optotype. Additional gap structures of the same average luminance, but different fineness, were inserted at the remaining potential gap locations, thereby balancing luminance across potential gap locations. Visual acuity measures were obtained for each optotype variant, using a computer-based test employing a staircase procedure.


Similar acuity values were obtained for all optotypes of the first group, and for standard Landolt Cs, irrespective of the fineness of the gap structure. With luminance-balanced optotypes of the second group, measured acuity was halved, compared to standard optotypes.


The results support the view that it is recognition acuity, rather than resolution acuity, which is measured with standard Landolt-style optotypes, with the imbalanced luminance distribution serving as a cue. Luminance-balanced optotypes may help to obtain a more veridical estimate of resolution acuity, although recognition acuity may be more relevant in daily living.


Visual acuity Shape perception Landolt C Resolution Recognition 



We are grateful to Felix Scharff for his help with collecting data, and we thank our subjects for their participation. The study was supported by the Deutsche Forschungsgemeinschaft (BA 877/18).


  1. 1.
    International Organization for Standardization (2009) ISO 8596, Ophthalmic optics—visual acuity testing—standard optotype and its presentation. International Organization for Standardization, GenevaGoogle Scholar
  2. 2.
    Lebensohn JE (1962) Snellen on visual acuity. Am J Ophthalmol 53:152–155PubMedGoogle Scholar
  3. 3.
    Liu L, Klein SA, Xue F, Zhang JY, Yu C (2009) Using geometric moments to explain human letter recognition near the acuity limit. J Vis 9:26.1–18CrossRefGoogle Scholar
  4. 4.
    Bondarko VM, Danilova MV (1997) What spatial frequency do we use to detect the orientation of a Landolt C? Vision Res 37:2153–2156PubMedCrossRefGoogle Scholar
  5. 5.
    McAnany JJ, Alexander KR (2008) Spatial frequencies used in Landolt C orientation judgments: relation to inferred magnocellular and parvocellular pathways. Vision Res 48:2615–2624PubMedCrossRefGoogle Scholar
  6. 6.
    Reich LN, Ekabutr M (2002) The effects of optical defocus on the legibility of the Tumbling-E and Landolt-C. Optom Vis Sci 79:389–393PubMedCrossRefGoogle Scholar
  7. 7.
    Pirenne MH (1962) Visual acuity. In: Davson H (ed) The eye: the visual process. Academic, New York, pp 175–195Google Scholar
  8. 8.
    Rea MS (ed) (2000) The IESNA lighting handbook, 9th edn. Illuminating Engineering Society of North America, New YorkGoogle Scholar
  9. 9.
    Pointer JS (2008) Recognition versus resolution: a comparison of visual acuity results using two-alternative test chart optotype. J Optom 1:65–70CrossRefGoogle Scholar
  10. 10.
    Lit A (1968) Visual acuity. Ann Rev Psychol 19:27–54CrossRefGoogle Scholar
  11. 11.
    González EG, Tarita-Nistor L, Markowitz SN, Steinbach MJ (2007) Computer-based test to measure optimal visual acuity in age-related macular degeneration. Invest Ophthalmol Vis Sci 48:4838–4845PubMedCrossRefGoogle Scholar
  12. 12.
    Wittich W, Overbury O, Kapusta MA, Watanabe DH (2006) Differences between recognition and resolution acuity in patients undergoing macular hole surgery. Invest Ophthalmol Vis Sci 47:3690–3694PubMedCrossRefGoogle Scholar
  13. 13.
    Plainis S, Tzatzala P, Orphanos Y, Tsilimbaris MK (2007) A modified ETDRS visual acuity chart for European-wide use. Optom Vis Sci 84:647–653PubMedCrossRefGoogle Scholar
  14. 14.
    Riggs LA (1965) Visual acuity. In: Graham CH (ed) Vision and visual perception. Wiley & Sons, New York, pp 321–349Google Scholar
  15. 15.
    Jänicke B, Schultz E (1994) Small and large field grating acuity versus recognition acuity in different groups of amblyopic patients. Strabismus 2:59–65PubMedCrossRefGoogle Scholar
  16. 16.
    Leat SJ, Yadav NK, Irving EL (2009) Development of visual acuity and contrast sensitivity in children. J Optom 2:19–26CrossRefGoogle Scholar
  17. 17.
    Schober H (1952) Untersuchungen über die Verwendbarkeit des Landoltschen Ringes als Normzeichen bei der Sehschärfebestimmung. Optik 9:225–235Google Scholar
  18. 18.
    Anderson RS, Thibos LN (1999) Relationship between acuity for gratings and for tumbling-E letters in peripheral vision. J Opt Soc Am A Opt Image Sci Vis 16:2321–2333PubMedCrossRefGoogle Scholar
  19. 19.
    Aulhorn E (1964) Über die Beziehung zwischen Lichtsinn und Sehschärfe. Albrecht Von Graefes Arch Ophthalmol 167:4–74PubMedGoogle Scholar
  20. 20.
    Kaernbach C (1991) Simple adaptive testing with the weighted up–down method. Percept Psychophys 49:227–229PubMedCrossRefGoogle Scholar
  21. 21.
    Heinrich SP, Krüger K, Bach M (2011) The dynamics of practice effects in an optotype acuity task. Graefes Arch Clin Exp Ophthalmol 249:1319–1326PubMedCrossRefGoogle Scholar
  22. 22.
    Pointer JS (1986) Toward the elimination of guessing bias in Landolt acuity testing. Am J Optom Physiol Opt 63:813–818PubMedCrossRefGoogle Scholar
  23. 23.
    Montagna B, Pestilli F, Carrasco M (2009) Attention trades off spatial acuity. Vision Res 49:735–745PubMedCrossRefGoogle Scholar
  24. 24.
    Ewing AE (1920) Test objects for the illiterate. Am J Ophthalmol 3:5–22Google Scholar
  25. 25.
    Dehnert A, Bach M, Heinrich SP (2011) Subjective visual acuity with simulated defocus. Ophthalmic Physiol Opt 31:625–631PubMedCrossRefGoogle Scholar
  26. 26.
    Weigmann U, Petersen J (1996) DIN-kompatible Visusbestimmung höherer Reproduzierbarkeit mit Staircase-Messung und Maximum-likelihood-Auswertung. Ophthalmologe 93:328–332PubMedGoogle Scholar
  27. 27.
    Bach M (2007) The Freiburg Visual Acuity Test—variability unchanged by post-hoc re-analysis. Graefes Arch Clin Exp Ophthalmol 245:965–971PubMedCrossRefGoogle Scholar
  28. 28.
    Heinrich SP, Krüger K, Bach M (2010) The effect of optotype presentation duration on acuity estimates revisited. Graefes Arch Clin Exp Ophthalmol 248:389–394PubMedCrossRefGoogle Scholar
  29. 29.
    Strasburger H (2001) Converting between measures of slope of the psychometric function. Percept Psychophys 63:1348–1355PubMedCrossRefGoogle Scholar
  30. 30.
    Stiers P, Vanderkelen R, Vandenbussche E (2003) Optotype and grating visual acuity in preschool children. Invest Ophthalmol Vis Sci 44:4123–4130PubMedCrossRefGoogle Scholar
  31. 31.
    Bondarko VM, Semenov LA (2005) Visual acuity and the crowding effect in 8- to 17-year-old schoolchildren. Hum Physiol 31:532–538CrossRefGoogle Scholar
  32. 32.
    Charman WN, Heron G (1988) Fluctuations in accommodation: a review. Ophthalmic Physiol Opt 8:153–164PubMedCrossRefGoogle Scholar
  33. 33.
    Stark L, Campbell FW, Atwood J (1958) Pupil unrest: an example of noise in a biological servomechanism. Nature 182:857–858PubMedCrossRefGoogle Scholar
  34. 34.
    Montés-Micó R (2007) Role of the tear film in the optical quality of the human eye. J Cataract Refract Surg 33:1631–1635PubMedCrossRefGoogle Scholar
  35. 35.
    Akutsu H, Bedell HE, Patel SS (2000) Recognition thresholds for letters with simulated dioptric blur. Optom Vis Sci 77:524–530PubMedCrossRefGoogle Scholar
  36. 36.
    Howland B, Ginsburg A, Campbell F (1978) High-pass spatial frequency letters as clinical optotypes. Vision Res 18:1063–1066PubMedCrossRefGoogle Scholar
  37. 37.
    Shah N, Dakin SC, Redmond T, Anderson RS (2011) Vanishing optotype acuity: repeatability and effect of the number of alternatives. Ophthalmic Physiol Opt 31:17–22PubMedCrossRefGoogle Scholar
  38. 38.
    Koskin SA, Boiko EV, Sobolev AF, Shelepin YE (2007) Mechanisms of recognition of the outlines of “vanishing” optotypes. Neurosci Behav Physiol 37:59–65PubMedCrossRefGoogle Scholar
  39. 39.
    Demirel S, Anderson RS, Dakin SC, Thibos LN (2012) Detection and resolution of vanishing optotype letters in central and peripheral vision. Vision Res 59:9–16PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.Sektion Funktionelle SehforschungUniv.-Augenklinik FreiburgFreiburgGermany

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