{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,24]],"date-time":"2026-09-24T00:51:42Z","timestamp":1790211102179,"version":"4.1.0"},"reference-count":53,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2023,12,11]],"date-time":"2023-12-11T00:00:00Z","timestamp":1702252800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JCM"],"abstract":"<jats:p>Visual acuity is one of the most important parameters for evaluating the vision of patients with keratoconus. This study reviewed 295 articles related to keratoconus published between 2017 and 2022 in which visual acuity was one of the parameters measured. The methodology of visual acuity testing in studies on keratoconus was thoroughly analyzed. The analysis showed that the most commonly indicated chart for testing visual acuity papers on keratoconus is the Snellen chart. It was shown that in 150 out of 295 articles, the authors do not describe the methodology for testing visual acuity. What is more, it was also shown that in 68 of the 295 articles which were analyzed, a procedure for converting visual acuity tested with a Snellen chart into a logMAR scale was used. In this review, we discuss the validity and reliability of such conversions. In particular, we show that insufficient description of visual acuity testing methodology and lack of information on the conversion of visual acuity results into the logMAR scale may contribute to the misinterpretation of visual acuity test results.<\/jats:p>","DOI":"10.3390\/jcm12247620","type":"journal-article","created":{"date-parts":[[2023,12,11]],"date-time":"2023-12-11T14:12:51Z","timestamp":1702303971000},"page":"7620","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Visual Acuity Examination Methodology in Keratoconus"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4386-1217","authenticated-orcid":false,"given":"Magdalena","family":"Nandzik","sequence":"first","affiliation":[{"name":"Department of Ophthalmology, District Railway Hospital in Katowice, Medical University of Silesia, 40-760 Katowice, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6707-5790","authenticated-orcid":false,"given":"Edward","family":"Wyl\u0119ga\u0142a","sequence":"additional","affiliation":[{"name":"Department of Ophthalmology, District Railway Hospital in Katowice, Medical University of Silesia, 40-760 Katowice, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7295-4936","authenticated-orcid":false,"given":"Adam","family":"Wyl\u0119ga\u0142a","sequence":"additional","affiliation":[{"name":"Department of Ophthalmology, District Railway Hospital in Katowice, Medical University of Silesia, 40-760 Katowice, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dominika","family":"Szkodny","sequence":"additional","affiliation":[{"name":"Department of Ophthalmology, District Railway Hospital in Katowice, Medical University of Silesia, 40-760 Katowice, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8083-3437","authenticated-orcid":false,"given":"Anna Maria","family":"Roszkowska","sequence":"additional","affiliation":[{"name":"Ophthalmology Clinic, Department of Biomedical Sciences, University of Messina, 98100 Messina, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ewa","family":"Wr\u00f3blewska-Czajka","sequence":"additional","affiliation":[{"name":"Department of Ophthalmology, District Railway Hospital in Katowice, Medical University of Silesia, 40-760 Katowice, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,12,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/S0896-1549(03)00013-0","article-title":"Visual acuity and its measurement","volume":"16","author":"Kniestedt","year":"2003","journal-title":"Ophthalmol. Clin. N. Am."},{"key":"ref_2","unstructured":"Azzam, D., and Ronquillo, Y. (2022). StatPearls, StatPearls Publishing."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2013","DOI":"10.1007\/s00417-014-2763-7","article-title":"Comparison of optotypes of Amsterdam Picture Chart with those of Tumbling-E, LEA Symbols, ETDRS, and Landolt-C in non-amblyopic and amblyopic patients","volume":"252","author":"Engin","year":"2014","journal-title":"Graefe\u2019s Arch. Clin. Exp. Ophthalmol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"631","DOI":"10.1111\/opo.12252","article-title":"Is it time to confine Snellen charts to the annals of history?","volume":"35","year":"2015","journal-title":"Ophthalmic Physiol. Opt."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"498","DOI":"10.1046\/j.1475-1313.1999.00460.x","article-title":"Chart construction and letter legibility\/readability","volume":"19","author":"McMonnies","year":"1999","journal-title":"Ophthalmic Physiol. Opt."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"740","DOI":"10.1097\/00006324-197611000-00006","article-title":"New Design Principles for Visual Acuity Letter Charts","volume":"53","author":"Bailey","year":"1976","journal-title":"Optom. Vis. Sci."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"432","DOI":"10.1136\/bjo.85.4.432","article-title":"The development of a \u201creduced logMAR\u201d visual acuity chart for use in routine clinical practice","volume":"85","author":"Rosser","year":"2001","journal-title":"Br. J. Ophthalmol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1016\/S0161-6420(96)30742-2","article-title":"Standardizing the Measurement of Visual Acuity for Clinical Research Studies","volume":"103","author":"Ferris","year":"1996","journal-title":"Ophthalmology"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"142","DOI":"10.1046\/j.1475-1313.2000.00490.x","article-title":"Letter legibility and chart equivalence","volume":"20","author":"McMonnies","year":"2000","journal-title":"Ophthalmic Physiol. Opt."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1465","DOI":"10.1007\/s00417-017-3659-0","article-title":"Reading charts in ophthalmology","volume":"255","author":"Radner","year":"2017","journal-title":"Graefe\u2019s Arch. Clin. Exp. Ophthalmol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"6","DOI":"10.1111\/j.1442-9071.2006.01135.x","article-title":"Changing from Snellen to LogMAR: Debate or delay?","volume":"34","author":"Hussain","year":"2006","journal-title":"Clin. Exp. Ophthalmol."},{"key":"ref_12","first-page":"441","article-title":"Has snellen chart lost the battle to etdrs in cataract surgery visual acuity evaluation?","volume":"60","year":"2022","journal-title":"Acta Clin. Croat."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"157","DOI":"10.1016\/j.clae.2010.04.006","article-title":"Keratoconus: A review","volume":"33","author":"Wolffsohn","year":"2010","journal-title":"Contact Lens Anterior Eye"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"770","DOI":"10.1016\/j.survophthal.2017.06.009","article-title":"A review of keratoconus: Diagnosis, pathophysiology, and genetics","volume":"62","author":"Tur","year":"2017","journal-title":"Surv. Ophthalmol."},{"key":"ref_15","unstructured":"Asimellis, G., and Kaufman, E.J. (2022, December 29). Keratoconus, Available online: https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK470435\/."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"293","DOI":"10.1016\/0039-6257(84)90094-8","article-title":"Keratoconus and related noninflammatory corneal thinning disorders","volume":"28","author":"Krachmer","year":"1984","journal-title":"Surv. Ophthalmol."},{"key":"ref_17","unstructured":"Vohra, V., Tuteja, S., Gurnani, B., and Chawla, H. (2022, December 29). Collagen Cross Linking for Keratoconus, Available online: https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK562271\/."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1016\/S0039-6257(97)00119-7","article-title":"Keratoconus","volume":"42","author":"Rabinowitz","year":"1998","journal-title":"Surv. Ophthalmol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"101559","DOI":"10.1016\/j.clae.2021.101559","article-title":"Keratoconus: An updated review","volume":"45","author":"Carracedo","year":"2022","journal-title":"Contact Lens Anterior Eye"},{"key":"ref_20","first-page":"289","article-title":"Improvement in Visual Acuity Six Months After Penetrating Keratoplasty In Patients Of Keratoconus","volume":"33","author":"Ansari","year":"2021","journal-title":"J. Ayub Med. Coll. Abbottabad-Pak."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Muijzer, M.B., Claessens, J.L., Cassano, F., Godefrooij, D.A., Prevoo, Y.F., and Wisse, R.P. (2021). The evaluation of a web-based tool for measuring the uncorrected visual acuity and refractive error in keratoconus eyes: A method comparison study. PLoS ONE, 16.","DOI":"10.1101\/2021.03.01.21252664"},{"key":"ref_22","first-page":"123","article-title":"Cross-linking treatment for better visual acuity","volume":"17","author":"Gilevska","year":"2020","journal-title":"Med. Glas."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1016\/j.joco.2016.10.004","article-title":"Effects of single-segment Intacs implantation on visual acuity and corneal topographic indices of keratoconus","volume":"29","author":"Amanzadeh","year":"2017","journal-title":"J. Curr. Ophthalmol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1016\/j.joco.2017.08.006","article-title":"A comparison of the visual acuity outcome between Clearkone and RGP lenses","volume":"30","author":"Hassani","year":"2018","journal-title":"J. Curr. Ophthalmol."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Liduma, S., Luguzis, A., and Krumina, G. (2020). The impact of irregular corneal shapeparameters on visual acuity and contrast sensitivity. BMC Ophthalmol., 20.","DOI":"10.1186\/s12886-020-01737-x"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"260","DOI":"10.4103\/jovr.jovr_30_16","article-title":"Evaluation of changes in visual acuity, contrast sensitivity and aberrations in patients with keratoconus after corneal collagen cross-linking","volume":"12","author":"Vejdani","year":"2017","journal-title":"J. Ophthalmic Vis. Res."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1654","DOI":"10.18240\/ijo.2019.10.21","article-title":"Management of cataract in keratoconus: Early visual outcomes of different treatment modalities","volume":"12","author":"Arej","year":"2019","journal-title":"Int. J. Ophthalmol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2477","DOI":"10.2147\/OPTH.S232954","article-title":"Visual and Refractive Long-Term Outcomes Following Standard Cross-Linking in Progressive Keratoconus Management","volume":"13","author":"Iqbal","year":"2019","journal-title":"Clin. Ophthalmol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1931","DOI":"10.2147\/OPTH.S139358","article-title":"Higher order optical aberrations and visual acuity in a randomized controlled trial comparing transepithelial versus epithelium-off corneal crosslinking for progressivekeratoconus","volume":"11","author":"Godefrooij","year":"2017","journal-title":"Clin. Ophthalmol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"23","DOI":"10.4103\/JOCO.JOCO_154_20","article-title":"Changes in the Optical Corneal Densitometry, Visual Acuity, and Refractive Error after the Annular Intracorneal Inlay Implantation","volume":"33","author":"Jabbarvand","year":"2021","journal-title":"J. Curr. Ophthalmol."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Csorba, A., Kr\u00e1nitz, K., Dorm\u00e1n, P., Popper-Sachetti, A., Kiss, H., Szalai, I., and Nagy, Z.Z. (2021). Factors influencing haze formation and corneal flattening, and the impact ofhaze on visual acuity after conventional collagen cross-linking: A 12-monthretrospective study. BMC Ophthalmol., 21.","DOI":"10.1186\/s12886-021-02066-3"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"3747","DOI":"10.2147\/OPTH.S275797","article-title":"Long-Term Visual, Refractive and Topographic Outcomes of \u201cEpi-off\u201d Corneal Collagen Cross-Linkingin Pediatric Keratoconus: Standard versus Accelerated Protocol","volume":"14","author":"Amer","year":"2020","journal-title":"Clin. Ophthalmol."},{"key":"ref_33","first-page":"385","article-title":"Comparison of visual and topographic outcomes of deep-anterior lamellar keratoplasty andpenetrating keratoplasty in keratoconus","volume":"10","author":"Kandemir","year":"2017","journal-title":"Int. J. Ophthalmol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"81","DOI":"10.2147\/OPTH.S120267","article-title":"Refractive and visual outcomesafter Keraring intrastromal corneal ring segment implantation for keratoconusassisted by femtosecond laser at 6 months follow-up","volume":"11","author":"Heikal","year":"2016","journal-title":"Clin. Ophthalmol."},{"key":"ref_35","first-page":"135","article-title":"The Effect of Age on Corneal Topographic Indices, Keratometry and Visual Acuity After Combined Intrastromal Corneal Ring Segment (ICRS) Implantation and Corneal Crosslinking","volume":"9","author":"Abdelmassih","year":"2020","journal-title":"Med. Hypothesis Discov. Innov. Ophthalmol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"370","DOI":"10.6061\/clinics\/2017(06)07","article-title":"Indications and visual outcomes of intrastromal corneal ring segment implantation in a large patient series","volume":"72","author":"Tognon","year":"2017","journal-title":"Clinics"},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Janiszewska-Bil, D., Czarnota-Nowakowska, B., Krysik, K., Lyssek-Boro\u0144, A., Dobrowolski, D., Grabarek, B.O., and Wyl\u0119ga\u0142a, E. (2021). Comparison of Long-Term Outcomes of the Lamellar and Penetrating Keratoplasty Approaches in Patients with Keratoconus. J. Clin. Med., 10.","DOI":"10.3390\/jcm10112421"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"2243","DOI":"10.2147\/OPTH.S227631","article-title":"Comparative Evaluation of Clinical Characteristics And Visual Outcomes Of Traumatic And Non-Traumatic Graft Dehiscence Following Corneal Transplantation Surgery","volume":"13","author":"Stevenson","year":"2019","journal-title":"Clin. Ophthalmol."},{"key":"ref_39","first-page":"949","article-title":"Impact of ultrasound and optical biometry on refractive outcomes of cataractsurgery after penetrating keratoplasty in keratoconus","volume":"18","author":"Krysik","year":"2019","journal-title":"Int. J. Ophthalmol."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/s40662-018-0127-9","article-title":"Refractive outcome of keratoconus treated by big-bubble deep anterior lamellarkeratoplasty in pediatric patients: Two-year follow-up comparison betweenmechanical trephine and femtosecond laser assisted techniques","volume":"6","author":"Buzzonetti","year":"2019","journal-title":"Eye Vis."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"5714372","DOI":"10.1155\/2017\/5714372","article-title":"Refractive, Topographic, and Aberrometric Results at 2-Year Follow-Up forAccelerated Corneal Cross-Link for Progressive Keratoconus","volume":"2017","author":"Bozkurt","year":"2017","journal-title":"J. Ophthalmol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"376","DOI":"10.4103\/jovr.jovr_42_17","article-title":"Visual and Refractive Outcomes and Tomographic Changes afterFemtosecond Laser-assisted Intrastromal Corneal Ring Segment Implantation inPatients with Keratoconus","volume":"13","author":"Hashemian","year":"2018","journal-title":"J. Ophthalmic Vis. Res."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"122","DOI":"10.22336\/rjo.2020.23","article-title":"Results in keratoconus correction with Kerasoft 3 Contact lenses","volume":"64","author":"Nicula","year":"2020","journal-title":"Rom. J. Ophthalmol."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"4321","DOI":"10.1167\/iovs.07-0511","article-title":"Uniformity of Visual Acuity Measures in Published Studies","volume":"49","author":"Williams","year":"2008","journal-title":"Invest. Ophthalmol. Vis. Sci."},{"key":"ref_45","unstructured":"Daiber, H.F., and Gnugnoli, D.M. (2023). StatPearls [Internet], StatPearls Publishing."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"224","DOI":"10.1016\/j.oret.2020.04.011","article-title":"Visual Acuity Variability: Comparing Discrepancies between Snellen and ETDRS Measurements among Subjects Entering Prospective Trials","volume":"5","author":"Hannah","year":"2021","journal-title":"Ophthalmol. Retin."},{"key":"ref_47","first-page":"311","article-title":"Prospective evaluation of visual acuity assessment: A comparison of snellen versus ETDRS charts in clinical practice (An AOS Thesis)","volume":"107","author":"Kaiser","year":"2009","journal-title":"Trans. Am. Ophthalmol. Soc."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"319","DOI":"10.1016\/j.ophtha.2007.05.028","article-title":"Comparison of Visual Acuity in Macular Degeneration Patients Measured with Snellen and Early Treatment Diabetic Retinopathy Study Charts","volume":"115","author":"Falkenstein","year":"2008","journal-title":"Ophthalmology"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"533","DOI":"10.1016\/j.ophtha.2022.12.008","article-title":"Comparison of Snellen Visual Acuity Measurements in Retinal Clinical Practice to Electronic ETDRS Protocol Visual Acuity Assessment","volume":"130","author":"Baker","year":"2023","journal-title":"Ophthalmology"},{"key":"ref_50","first-page":"82","article-title":"Comparison of Static Visual Acuity between Snellen and Early Treatment Diabetic Retinopathy Study Charts","volume":"2","author":"Kalpana","year":"2013","journal-title":"Int. J. Educ. Res. Dev."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"355","DOI":"10.1111\/opo.12310","article-title":"The good (logMAR), the bad (Snellen) and the ugly (BCVA, number of letters read) of visual acuity measurement","volume":"36","author":"Elliott","year":"2016","journal-title":"Ophthalmic Physiol. Opt."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"183","DOI":"10.1016\/j.optom.2020.04.001","article-title":"Refractive characteristics of keratoconus eyes with corneal Vogt\u2019s striae: A contralateral eye study","volume":"14","author":"Rakhshandadi","year":"2021","journal-title":"J. Optometry"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"100372","DOI":"10.1016\/j.xops.2023.100372","article-title":"Magnitude of Visual Acuity Change with ETDRS versus Snellen Testing in Clinical Trials: Implications for Clinic-Based Outcomes","volume":"4","author":"Salabati","year":"2024","journal-title":"Ophthalmol. Sci."}],"container-title":["Journal of Clinical Medicine"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2077-0383\/12\/24\/7620\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T21:36:43Z","timestamp":1760132203000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2077-0383\/12\/24\/7620"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,12,11]]},"references-count":53,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2023,12]]}},"alternative-id":["jcm12247620"],"URL":"https:\/\/doi.org\/10.3390\/jcm12247620","relation":{},"ISSN":["2077-0383"],"issn-type":[{"value":"2077-0383","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,12,11]]}}}