Visual acuity (VA), the cornerstone of eyecare, can yield symptoms despite 20/20 [1]. Optimal VA is 20/10 based on cone spacing. Vernier acuity (minimum misalignment) is 3” arc, 10x < 

cone spacing, a _hyperacuity_ mediated by visual cortex [2,3,4]. Minimum visible acuity [2] (MVA, thinnest black line detectable on white background) is 1” arc. Hence MVA (pilot avoiding

fine wire), is a potential hyperacuity never used clinically. We describe a cone specific test of MVA, including monocular, binocular, chromatic, and orientation specific performance.

Twenty-five healthy young adults (VA ≥ 20/30, mean age ± SD: 26 ± 3, 13 females) participated in our IRB approved protocol after written informed consent. MVA stimuli were 1.4° vertical,

128%: S cones due to sparse distribution and lower CS [5]. Line thicknesses varied from 60” to 10” arc in 0.16 log steps (16 stimuli/thickness level, 4 orientations, 4 colors). Each trial

consisted of a single line centered on the display wherein subjects identified stimulus orientation and color (0.01 log units/trial, Fig. 1a). Contrast, orientation, eye tested were

randomized across trials. Binocular followed monocular to minimize learning. Monocular (_P_ > 0.18) and binocular (_P_ > 0.47) MVA log thresholds were distributed normally

(Jarque–Berra test). Repeated-measures ANOVA, paired t-tests (Bonferroni correction) and Bland-Altman were used for analyses. Repeated measures ANOVA across eye tested and cone type showed

significant effects of eye (F = 15.5, _P_ < 0.001) and cone type (F = 50.8, _P_ < 0.001). Since MVA was not different between right and left eyes (_P_ > 0.73) means were used for

monocular analyses. The coefficient of repeatability, 95% confidence interval (CI) for within-patient change, was 0.3 log thickness (2” arc, Bland Altman, Fig. 1b). Across all colors, mean

binocular threshold (1.12 log s, 13”) was significantly lower than monocular (1.30, 20”, mean difference 0.18 log s, 95% CI 0.16–0.20, _P_ < 0.001, Fig. 2a). There was no difference

between L, M and grey MVA thresholds (_P_ > 0.32) while both S cone monocular MVA (1.40) was reduced vs. L, M, luminance (1.26, mean difference 0.14, 95% CI 0.09–0.17, _P_ < 0.001) as

was S cone binocular MVA (difference 0.08, 95% CI 0.04–0.13, _P_ < 0.001, Fig. 2b). Binocular S cone MVA was decreased for oblique vs. horizontal/vertical (_P_ < 0.02). Binocular L

cone MVA was improved for horizontal compared to vertical (_P_ < 0.001). MVA binocular and orientation effects support cortical processing. Decreased S cone MVA reflects the paucity of S

cones. 50% enhancement of binocular vs. monocular MVA exceeds 40% for CS indicating binocular cortical processing. Improved L cone binocular horizontal MVA may increase disparity enhancing

stereoacuity. MVA shows promise for disease detection/monitoring, occupational application, and as an outcome for gene therapy. Ongoing research is assessing age, orientation, and color

naming. Preliminary results show high sensitivity for detection of color deficiency and improvement with color correcting lenses. REFERENCES * Rabin J, Gooch J, Ivan D, Harvey R, Aaron M.

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Research reported in this publication was supported by the National Eye Institute of the National Institutes of Health under Award Number T35EY032441. The content is solely the

responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Open access funding provided by SCELC, Statewide California

Electronic Library Consortium. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * University of the Incarnate Word Rosenberg School of Optometry, San Antonio, TX, USA Jeff Rabin, Katelyn Goodroe,

 Alyssa Hood, Cara Duka, Kyle Dunmon, Darien Bouaphavong & Thinh Truong Authors * Jeff Rabin View author publications You can also search for this author inPubMed Google Scholar *

Katelyn Goodroe View author publications You can also search for this author inPubMed Google Scholar * Alyssa Hood View author publications You can also search for this author inPubMed 

Google Scholar * Cara Duka View author publications You can also search for this author inPubMed Google Scholar * Kyle Dunmon View author publications You can also search for this author

inPubMed Google Scholar * Darien Bouaphavong View author publications You can also search for this author inPubMed Google Scholar * Thinh Truong View author publications You can also search

for this author inPubMed Google Scholar CONTRIBUTIONS JR was responsible for designing the protocol, data collection, results interpretation and analyses, manuscript writing, and research

oversight. KG, AH, CD, KD, DB, and TT were responsible for designing the protocol, data collection, collating data, data curation, results interpretation and analyses. Contributions and

access to data: The Principal Investigator, Jeff Rabin, had full access to all data and takes responsibility for the integrity of the data and the accuracy of the data analysis.

CORRESPONDING AUTHOR Correspondence to Jeff Rabin. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing interests. ADDITIONAL INFORMATION PUBLISHER’S NOTE Springer Nature

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http://creativecommons.org/licenses/by/4.0/. Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Rabin, J., Goodroe, K., Hood, A. _et al._ Minimum visual acuity: a new cone

specific clinical test. _Eye_ 39, 195–197 (2025). https://doi.org/10.1038/s41433-024-03377-7 Download citation * Received: 14 September 2024 * Revised: 18 September 2024 * Accepted: 23

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