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Open Access

Peer-reviewed

Research Article

Low contrast visual acuity in healthy adults: Impact on non-pathologic myopia

  • Toshio Narimatsu,

    Roles Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Software, Validation, Visualization, Writing – original draft

    Affiliations Department of Clinical Regenerative Medicine, Fujita Health University School of Medicine, Ota, Tokyo, Japan, Fujita Medical Innovation Center Tokyo, Ota, Tokyo, Japan, Eye Center, Fujita Health University Haneda Clinic, Ota, Tokyo, Japan

    ⨯
  • Noriko Onozato,

    Roles Data curation, Resources, Writing – review & editing

    Affiliations Fujita Medical Innovation Center Tokyo, Ota, Tokyo, Japan, Eye Center, Fujita Health University Haneda Clinic, Ota, Tokyo, Japan

    ⨯
  • Haruna Togawa,

    Roles Data curation, Resources, Writing – review & editing

    Affiliations Fujita Medical Innovation Center Tokyo, Ota, Tokyo, Japan, Eye Center, Fujita Health University Haneda Clinic, Ota, Tokyo, Japan

    ⨯
  • Shigeto Shimmura,

    Roles Writing – review & editing

    Affiliations Department of Clinical Regenerative Medicine, Fujita Health University School of Medicine, Ota, Tokyo, Japan, Fujita Medical Innovation Center Tokyo, Ota, Tokyo, Japan, Eye Center, Fujita Health University Haneda Clinic, Ota, Tokyo, Japan

    ⨯
  • Yoko Ozawa

    Roles Conceptualization, Formal analysis, Funding acquisition, Methodology, Project administration, Supervision, Writing – original draft

    yoko.ozawa@fujita-hu.ac.jp, ozawa.a5@keio.jp

    Affiliations Department of Clinical Regenerative Medicine, Fujita Health University School of Medicine, Ota, Tokyo, Japan, Fujita Medical Innovation Center Tokyo, Ota, Tokyo, Japan, Eye Center, Fujita Health University Haneda Clinic, Ota, Tokyo, Japan, Department of Ophthalmology, Keio University School of Medicine, Shinjuku, Tokyo, Japan

    ⨯

Abstract

Increase in myopia is a social issue worldwide. However, whether non-pathologic myopia with normal best-corrected visual acuity (BCVA) exhibits differences in visual ability is not well-documented. Data of 43 healthy eyes in 43 participants (52.8 ± 6.07 years) including 13 (30.2%) males who underwent eye medical checkups at Fujita Medical Innovation Center, Tokyo were retrospectively analyzed. Eyes with general BCVA 0 in logMAR or better and without histories of ocular diseases and surgeries were included. Mean low-contrast visual acuity (LCVA) measured using grey-scale optotypes with best correction was 0.17 ± 0.13 (range, −0.079–0.53; median, 0.15). LCVA was correlated with age (r = 0.2634, 95% confidence interval [CI] −0.040–0.522, P = 0.039). Eyes with LCVA better than 0.15 was associated with uncorrected visual acuity (OR, 43.425; 95%CI, 3.729–1250.027; P = 0.010), subjective spherical equivalent (OR, 1.761; 95%CI, 1.255–2.776; P = 0.004), subjective spherical power (OR, 1.616; 95%CI, 1.186–2.433; P = 0.008), and axial length (OR, 0.550; 95%CI, 0.293–0.951; P = 0.032) after adjusted for age and sex. Mean LCVA of less myopic eyes with spherical equivalent > −3.0 diopters was 0.12 ± 0.10 (median, 0.10), and that of more myopic eyes was 0.23 ± 0.14 (median, 0.22) (P < 0.001). Non-pathological myopic eyes exhibited worse LCVA under best correction and had a risk of worse visual ability.

Citation: Narimatsu T, Onozato N, Togawa H, Shimmura S, Ozawa Y (2026) Low contrast visual acuity in healthy adults: Impact on non-pathologic myopia. PLoS One 21(9): e0357713. https://doi.org/10.1371/journal.pone.0357713

Editor: Tatsuya Inoue, Yokohama City University, JAPAN

Received: June 10, 2026; Accepted: August 20, 2026; Published: September 21, 2026

Copyright: © 2026 Narimatsu et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting Information files.

Funding: - YO: 24K12792 - Japan Society for the Promotion of Science (JSPS KAKENHI) - https://www.jsps.go.jp/english/e-grants/ - The funders did not play any role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. - TN: 25K24047 - Japan Society for the Promotion of Science (JSPS KAKENHI) - https://www.jsps.go.jp/english/e-grants/ - The funders did not play any role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Increase in myopia is a social issue worldwide [1,2]. Preventive therapy for myopia progression in children attracts attention, anticipating reduction of the risk of pathologic myopia which causes substantial visual loss [3–6]. However, whether there is an influence of non-pathologic myopia on visual ability has not been well-documented.

In contrast to pathologic myopia which causes irreversible visual loss due to macular atrophy and neovascularization, non-pathologic myopia may not cause severe visual loss. Most of the non-pathological myopic eyes exhibit normal best-corrected visual acuity (BCVA), 0 in logMAR or better, and evaluated as non-diseased, and healthy eyes in daily clinic.

Low-contrast visual acuity (LCVA) is measured using low-contrast and grey-scale optotypes under best correction in contrast to general BCVA measurement using black optotypes. Because LCVA is measured under more stringent conditions than general BCVA, LCVA is utilized in clinical studies to detect subtle changes in visual acuity [7,8]. LCVA has been used to show the treatment effect of an anti-vascular endothelial growth factor therapy in eyes with age-related macular degeneration, which exhibited relatively good BCVA at baseline compared with the phase III study [7]. In the prospective study, mean general BCVA at baseline was 0.07 in logMAR and good, thus, there had been a concern in detecting the visual improvement after therapy due to ceiling effect. However, visual improvement was clearly shown using LCVA score [7]. It is also used in the studies to show the visual impairment in brain and/or optic nerve damage by classical galactosemia [9] and multiple sclerosis [10,11], as well as in the retinal damage due to central serous chorioretinopathy [12].

In this study, LCVA of healthy eyes with various refraction errors were analyzed to show differences in visual ability. The information will help understand the impact of non-pathologic myopia on vision, and also the usage of LCVA in future clinical studies as well as clinical practices.

Methods

Participants

The participants were those who underwent eye medical checkups at Fujita Medical Innovation Center, Tokyo, Japan, from February to December 2025. Those who exhibited BCVA worse than 0 in logMAR were excluded. Those with eye diseases such as glaucoma, age-related macular degeneration, epiretinal membrane, diabetic retinopathy, pathologic myopia defined by presence of myopic maculopathy category 2 or above, or presence of posterior staphyloma [13], macular dystrophy, retinitis pigmentosa, and noticeable cataract, or those with histories of ocular surgeries, such as cataract surgery, implantable contact lens surgery, and laser-assisted in situ keratomileusis, were also excluded. The left eyes of the participants were evaluated.

This study adhered to the principles of the Declaration of Helsinki and was approved by the Fujita Health University Ethics Committee (approval number: HM25–294). Written informed consent was obtained from all the participants to use their data for research purposes.

Eye examinations

All patients underwent BCVA measurement based on refraction tests, slit-lamp examinations, and fundus examinations. LCVA was tested with the best correction, with the same correction as the BCVA measurement, by showing Landolt C optotypes of Landolt C charts with 6% contrast one by one on the display using SC-1600 (NIDEK Co., LTD, Aichi, Japan). The axial length was measured using ARGOS (Alcon Laboratories, Inc., TX, USA). Cornea/anterior segment optical coherence tomography (OCT) (Tomey Corporation, Aichi, Japan), Heidelberg Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany), and ultrawide field color fundus camera system, Optos (Nikon Corporation, Tokyo, Japan), were used to record images. Subjective spherical equivalent, spherical, and cylindrical powers were evaluated from data obtained by a subjective refraction test performed by the orthoptists after measuring objective refractions by autorefractometer (TRK-2P, Topcon, Tokyo, Japan).

Statistical analyses

JMP (student edition, JMP Statistical Discovery LLC, NC, USA) was used for all the statistical analyses. Data are presented as the mean ± standard deviation values. Spearman’s rank correlation coefficient analyses, logistic regression analyses, and Mann-Whitney U test were used. Statistical significance was set at P < 0.05.

Results

Mean age of the 43 participants, all of whom exhibited BCVA better than 0 in logMAR (1.0 in decimal, 20/20 in Snellen chart) was 52.8 ± 6.07 (range, 44–66; [median 52]) years, and 13 (30.2%) were males (Table 1). Mean LCVA was 0.17 ± 0.13 (−0.079 to 0.53 [0.15]) in logMAR; the measurement was performed using Landolt C chart with decimal score, thus the values were originally recorded in decimal score and converted into logMAR. The measured decimal score ranged 0.3 to 1.2, their mean value was 0.70 ± 0.19, and median value was 0.7. Mean spherical equivalent of the eyes was −3.49 ± 2.78 (+1.63 to −10.88 [−3.13]) diopters. All the eyes were phakic with no history of eye surgeries. There were 15 eyes with conus, and 5 eyes with fundas tessellation as observed in fundus photograph although there were no eyes with macular lesions.

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Table 1. Characteristics of the participants.

https://doi.org/10.1371/journal.pone.0357713.t001

LCVA was positively correlated with age (Fig 1, Table 2) (r = 0.2634, 95% confidence interval [CI] −0.040 to 0.522, P = 0.039). Other studied parameters, except for lens thickness, were not correlated with age (Table 2).

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Table 2. Correlations between ocular parameters and age.

https://doi.org/10.1371/journal.pone.0357713.t002

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Fig 1. Correlation between low-contrast visual acuity (LCVA) and age.

LCVA was positively correlated with age (r = 0.2634, 95% confidence interval [CI] −0.040 to 0.522, P = 0.039).

https://doi.org/10.1371/journal.pone.0357713.g001

Next, the eyes were divided into two groups; eyes which exhibited better LCVA than the median value, 0.15, and those that were worse. The factors associated with better LCVA were analyzed using logistic regression analyses (Table 3). The better LCVA was associated with uncorrected visual acuity (OR, 43.425; 95% CI 3.729–1250.027; P = 0.010), subjective spherical equivalent (OR, 1.761; 95% CI 1.255–2.776; P = 0.004), subjective spherical power (OR, 1.616; 95% CI 1.186–2.433; P = 0.008), and axial length (OR, 0.550; 95% CI 0.293–0.951; P = 0.032) after adjusted for age and sex.

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Table 3. Factors associated with low-contrast visual acuity in healthy adults.

https://doi.org/10.1371/journal.pone.0357713.t003

Correlations between LCVA and SE were also significant (Fig 2) (r = −0.5501, 95% CI −0.730– −0.299, P = 0.0019).

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Fig 2. Correlation between low-contrast visual acuity (LCVA) and spherical equivalent (SE).

LCVA was positively correlated with SE (r = −0.5501, 95% confidence interval [CI] −0.730 to −0.299, P = 0.0019).

https://doi.org/10.1371/journal.pone.0357713.g002

We then analyzed the cut-off values of parameters which were related to better LCVA using receiver operating characteristic (ROC) curves. Eyes with better uncorrected visual acuity than 0.70 in logMAR (area under the concentration-time curve [AUC], 0.765), subjective spherical equivalent > −3.0 diopters (0.780), subjective spherical power > −2.5 diopter (0.740), and shorter axial length < 25.3 mm (0.680) more frequently exhibited better LCVA.

The eyes were divided according to the spherical equivalent, and mean values of LCVA in eyes with or without spherical equivalent > −3.0 diopters were analyzed (Table 4). Mean LCVA of the less myopic and hyperopic eyes with subjective spherical equivalent > −3.0 diopters was 0.12 ± 0.10 (median, 0.10) in logMAR (0.79 ± 0.17 [median, 0.8] in decimal), and that of more myopic eyes was 0.23 ± 0.14 (median, 0.22) in logMAR (0.62 ± 0.18 [median, 0.6] in decimal). There was a significant difference between the groups (P < 0.01).

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Table 4. Mean and median values of low-contrast visual acuity according to the refraction error.

https://doi.org/10.1371/journal.pone.0357713.t004

Discussion

Mean LCVA of healthy adults was 0.17 ± 0.13 in logMAR and median LCVA was 0.15 in logMAR. LCVA was positively correlated with age, and better LCVA was observed in eyes with better uncorrected visual acuity, less myopia, and shorter axial length, after adjusted for age and sex. LCVA was correlated with SE. Less myopic eyes with subjective spherical equivalent > −3.0 diopters more frequently exhibited better LCVA, and their median was 0.10, while that of more myopic eyes was 0.22 in logMAR.

Healthy people are supposed to exhibit a BCVA better than 0 in logMAR; however, LCVA, in which the best correction was provided, but the low contrast optotypes were presented, ranged between −0.079 and 0.53 in logMAR and varied among the healthy individuals. Referring to the median value, an LCVA better than 0.15 in logMAR would be more appropriate to represent eyes with better visual function among healthy adults.

LCVA correlated with age in the current study using 6% low-contrast visual chart. This was consistent with the previous study using 2.5% low contrast chart in which the mean value decreased every decade [14,15]. The current study also showed that the lens thickness increased with age, suggesting a certain influence of lens aging. Given that there were no participants who had already had cataract surgery, age-related progress in lens opacity, if any, could have affected LCVA, although all the eyes exhibited better general BCVA than 0 in logMAR. Alternatively, the number of photoreceptors [16] and retinal pigment epithelial [17] cells, as well as the function of retinal ganglion cells [18] are reportedly reduced as age increases in eyes with no disease, and retinal aging may also have been an effect.

When adjusted for age and sex, eyes with a better LCVA often had less myopia, and this was consistent with the result that eyes with a better LCVA often exhibited shorter axial length. The eyes with better LCVA exhibited good uncorrected visual acuity, most likely related to less involvement of myopia. None of the eyes had any macular lesions; however, the non-pathologic myopia was related to impairment of LCVA even after best correction. In addition, the median values of LCVA in moderate to highly myopic eyes were worse than non-myopic to mildly myopic eyes. Thus, there would be an inferiority in the ability to see in non-pathological myopic eyes. Preventive treatments against myopia progression in children [3–6] may also be valuable for maintaining visual ability under the best correction. Future studies can include LCVA to assess the importance of myopia suppression to preserve better visual ability in non-pathologic myopia.

Myopic eyes exhibit higher-order aberrations (HOAs) that are subtle and complex refractive errors [19]. It is optical imperfections of the eye that alter retinal image ability despite optimal correction of spherical defocus and astigmatism [20]. HOAs can be related to lens shape and position [19]. Among highly myopic eyes < −6.0 diopters in Chinese participants, greater HOAs were associated with reduced visual acuity in simulated night conditions, and decreased contrast sensitivity under mesopic and simulated night conditions [21]. Similar mechanisms may have affected LCVA and visual ability in eyes with spherical equivalent ≤ −3.0 diopters in the current study. Alternatively, central cone photoreceptor density reportedly tends to be reduced as axial length becomes longer [22], which could have influenced LCVA in myopic eyes. Further studies are required to estimate the mechanisms.

Limitations of this study included a relatively small sample size, a retrospective design, and refractive corrections performed with spectacle frames rather than contact lenses. Thus, very highly myopic eyes, such as those with −10.0 diopters, may have been affected by the aberration effects due to thick lenses during LCVA measurement; however, the inferiority of LCVA was also observed in the eyes with −3.0 diopters, and the confounding effect may not be involved in most of the eyes. Evaluation of cataract, if any, was performed only using slit lamp examinations by well-trained ophthalmologists, but not by image data. However, all the participants exhibited no or slight to mild cataract and BCVA of 0 in logMAR or better.

We measured 6% LCVA in healthy participants and found that visual ability varied among individuals without eye diseases. The factors associated with LCVA were not only age. LCVA of better than median value was more frequently observed in eyes with non- to mild myopia (> −3.0 diopters) and shorter axial length (≤ 25.3 mm). Thus, non-pathologic myopia exhibited worse LCVA. The current results may help appropriately evaluate LCVA in clinical practices and clinical trials. Further studies are warranted.

Acknowledgments

We appreciate all the members of Haneda Clinic, Fujita Medical Innovation Center Tokyo for their kind assistance.

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