June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Modeling the relationship between VA measured with Snellen and ETDRS standards
Author Affiliations & Notes
  • Michael Dorr
    Adaptive Sensory Technology, San Diego, California, United States
  • Yukai Zhao
    Center for Neuroscience, New York University, New York, New York, United States
  • Luis A Lesmes
    Adaptive Sensory Technology, San Diego, California, United States
  • Zhong-Lin Lu
    Division of Arts and Sciences, New York University Shanghai, Shanghai, Shanghai, China
    Center for Neuroscience, New York University, New York, New York, United States
  • Footnotes
    Commercial Relationships   Michael Dorr Adaptive Sensory Technology, Inc., Code E (Employment), Adaptive Sensory Technology, Inc., Code I (Personal Financial Interest), Adaptive Sensory Technology, Inc., Code P (Patent); Yukai Zhao None; Luis Lesmes Adaptive Sensory Technology, Inc., Code E (Employment), Adaptive Sensory Technology, Inc., Code I (Personal Financial Interest), Adaptive Sensory Technology, Inc., Code P (Patent); Zhong-Lin Lu Adaptive Sensory Technology, Inc., Code I (Personal Financial Interest), Adaptive Sensory Technology, Inc., The Ohio State University, Code P (Patent)
  • Footnotes
    Support  EY017491
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 2554 – F0508. doi:
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    • Get Citation

      Michael Dorr, Yukai Zhao, Luis A Lesmes, Zhong-Lin Lu; Modeling the relationship between VA measured with Snellen and ETDRS standards. Invest. Ophthalmol. Vis. Sci. 2022;63(7):2554 – F0508.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Visual acuity (VA) is measured with the ETDRS standard in clinical trials. Snellen remains the real-world standard, although Snellen VA is typically worse by 6 ~ 12 letters (0.12 ~ 0.24 LogMAR). In this study, we modeled ETDRS-Snellen discrepancies for 163 observers from Kaiser (2009) to enable better translation between the VA standards.

Methods : We used a VA behavioral function to simulate VA behavior for 27 observers with VA threshold τ from -0.3 to 2.3 LogMAR and VA-dependent range 0.253 + 0.185 VA LogMAR (Zhao et al. 2021). We scored VA behavior using ETDRS and Snellen rules (Kaiser, 2009). From repeated simulations of each observer, we computed the mean and standard deviation (SD) of VA scores and modeled ETDRS-Snellen score pairs using maximum likelihood.

Results : For the two charts, Figure 1 shows the bias (deviation from identity line) and variability (SD) of VA scores. Small biases observed when τ < 1.0 LogMAR increased significantly as VA worsened: bias > 0.20-0.50 LogMAR as τ > 1.0 LogMAR. Likewise, variability increased for worse VA: SD up to 0.15 for ETDRS and 0.19 for Snellen. Results from each simulated observer were used to construct the probability distributions for ETDRS-Snellen score pairs (Figure 2A). They were used to successfully model all the ETDRS and Snellen scores (Figure 2B) in Kaiser (2009) (p > .05 for all differences between observed scores and model predictions).

Conclusions : Using a VA behavioral function, we successfully modeled discrepancies between ETDRS and Snellen scores from a large sample of subjects with a wide range of VA scores. The model can be used to translate between VA measured in trials and real world.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

(A) Expected VA scores. (B) SD.

(A) Expected VA scores. (B) SD.

 

(A) Two-dimensional ETDRS and Snellen score distributions for five simulated observers. (B) Best fits to the data in Kaiser (2009).

(A) Two-dimensional ETDRS and Snellen score distributions for five simulated observers. (B) Best fits to the data in Kaiser (2009).

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