June 2020
Volume 61, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2020
Visual Acuity Variability: Comparing Discrepancies Between Snellen and ETDRS Measurements Among Subjects Entering Prospective Clinical Trials
Author Affiliations & Notes
  • Hannah Yu
    Retina Consultants of Houston, Houston, Texas, United States
  • Peter M Kaiser
    Vitreoretinal Service, Cole Eye Institute, Cleveland, Ohio, United States
  • Deneva Zamora
    Retina Consultants of Houston, Houston, Texas, United States
  • Melisa Bocanegra
    Retina Consultants of Houston, Houston, Texas, United States
  • Cassandra Cone
    Retina Consultants of Houston, Houston, Texas, United States
  • David M Brown
    Retina Consultants of Houston, Houston, Texas, United States
    Blanton Eye Institute, Houston Methodist Hospital & Weill Cornell Medical College, Houston, Texas, United States
  • Srinivas Sadda
    Doheny Image Reading Center, Doheny Eye Institute, Los Angeles, California, United States
    Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, California, United States
  • Charles Clifton Wykoff
    Retina Consultants of Houston, Houston, Texas, United States
    Blanton Eye Institute, Houston Methodist Hospital & Weill Cornell Medical College, Houston, Texas, United States
  • Footnotes
    Commercial Relationships   Hannah Yu, None; Peter Kaiser, Aerie (C), Aerpio (C), Alcon (C), Allegro (C), Allergan (C), Biogen Idec (C), Boerenger Ingelheim (C), Clearside Biomedical (C), Kanghong (C), Kodiak (C), NGM Biopharmaceuticals (C), Novartis (C), Ocugenix (C), Oculix (C), Opthea (C), Regeneron (C), RegenexBio (C), SciFluor (C), Shire (C), Spark (C), Stealth (C), Takeda (C); Deneva Zamora, None; Melisa Bocanegra, None; Cassandra Cone, None; David Brown, Adverum (C), Allegro (C), Apellis (C), Bayer (C), Boehringer Ingelheim (C), ChengduKanghong Biotechnology (C), Gemini (C), Genentech/Roche (C), iRenix Lineage Cell (C), Kodiak (C), Navilas (C), Novartis (C), Ocular Therapeutics (C), Optos (C), Regeneron (C), Regenxbio (C), Santen (C), Senju (C), Stealth (C); Srinivas Sadda, 4DMT (C), Allergan (C), Amgen (C), Bayer (C), Carl Zeiss Meditec (F), Centervue (C), Genentech/Roche (C), Heidelberg Engineering (C), Heidelberg Engineering (F), Novartis (C), Optos (C), Optos (F), Oxurion (C), Regeneron (C); Charles Wykoff, Adverum (C), Aerpio (C), Alimera Sciences (C), Allegro (C), Allergan (C), Apellis (C), Bayer (C), Chengdu Kanghong (C), Clearside Biomedical (C), Genentech/Roche (C), Graybug Vision (F), IONIS Pharmaceuticals (F), Iveric Bio (C), Kodiak (C), Neurotech (F), Novartis (C), Opthea (F), Recens Medical (C), Regeneron (C), Regenxbio (C), Samsung (F)
  • Footnotes
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Investigative Ophthalmology & Visual Science June 2020, Vol.61, 2652. doi:
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    • Get Citation

      Hannah Yu, Peter M Kaiser, Deneva Zamora, Melisa Bocanegra, Cassandra Cone, David M Brown, Srinivas Sadda, Charles Clifton Wykoff; Visual Acuity Variability: Comparing Discrepancies Between Snellen and ETDRS Measurements Among Subjects Entering Prospective Clinical Trials. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2652.

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

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Abstract

Purpose : Early Treatment Diabetic Retinopathy Study (ETDRS) best corrected visual acuity (BCVA) testing is a validated outcome in ophthalmic clinical trials. However, ETDRS measurements can differ meaningfully from Snellen VA measurements, creating challenges for comparing trial outcomes with data from routine clinical practice. This study compared the variability between ETDRS BCVA and Snellen measurements.

Methods : Information was retrospectively collected for subjects entering 12 prospective retina trials. Eyes were included if Snellen VA measurement was performed in clinic at the visit preceding trial screening and VA was better than counting fingers. Snellen VA and ETDRS BCVA were converted to logMAR. Variability between measurements was evaluated using Student’s t-test, Pearson’s test, and linear regression in the context of days between exams, disease state, absolute VA, and central subfield thickness (CST).

Results : 773 eyes of 391 patients were identified with a mean of 27.2 days (median 19; 95% CI 25.1-29.3) between measurements. Mean Snellen and ETDRS measurements were 0.40 (20/50) and 0.27 logMAR (20/40), respectively. Overall, mean ETDRS BCVA was 6.1 letters better than Snellen VA (median 5.8; 95% CI 5.3-7.0; p<0.05); 76.6% of eyes had improved ETDRS. Restricting the number of days between measurements did not result in any meaningful differences from this directionality. Among eyes with worse VA, variation was more pronounced than among eyes with better VA; eyes 20/25 or better were 1.9 mean letters better with ETDRS (p<0.05) and eyes 20/160 or worse were 12.6 mean letters better (p<0.05). Subgroup analyses by disease state found statistically significantly better ETDRS measurements compared to Snellen in four of the five disease states studied. While lens status did not impact extent of discrepancy between ETDRS and Snellen measurements, amount of retinal edema (CST) did: increased CST correlated with increased variability.

Conclusions : ETDRS BCVA resulted in significantly better scores when compared with Snellen VA measurements. This difference was more pronounced among eyes with worse VA. Additionally, specific retinal disease states and anatomic variables, such as extent of retinal edema (CST), may have a meaningful impact on the anticipated variability between ETDRS and Snellen measurements.

This is a 2020 ARVO Annual Meeting abstract.

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