The formula to convert Snellen visual acuity measurements to approxETDRS letter scores is 85 + 50 x log (Snellen fraction), which may be rounded to the nearest letter. Snellen "+/-" entries However, visual acuity measurements expressed as logMAR units are not intuitively interpretable by clinicians. Although there seems to be no good statistical reason to convert endobj Switching to brolucizumab: injection intervals and visual, anatomical and safety outcomes at 12 and 18months in real-world eyes with neovascular age-related macular degeneration. - https://doi.org/10.1167/iovs.05-0981 Conclusion: This is a common misconception). Or, arguably more appropriate in R, character coding for a categorical variable: you can change those codes with set_eye_strings(). Since 1990, M&S Technologies has served eye care professionals. endobj Google Scholar, Department of Ophthalmology, University Hospitals of Leicester NHS Trust, Infirmary Square, Leicester, LE1 5WW, UK, Stephenie Tiew,Christina Lim&Tharsica Sivagnanasithiyar, You can also search for this author in The formula is subsequently validated with manual conversion by two independent clinicians (CL and TS). Conversion of Snellen visual acuity fractions to approxETDRS letter scores for the purpose of performing statistical manipulations provides more readily interpretable outcomes compared with the current strategy of converting Snellen visual acuity fractions to logMAR units. Factors Contributing to Discrepancy Between Visual Acuity Fractions Derived From a Snellen Chart and Letter Scores on the Early Treatment Diabetic Retinopathy Study Chart. Ovid Technologies (Wolters Kluwer Health): 104650. Purpose: 13 0 obj Could be snellen, logmar, snellendec, etdrs, #> 6x NA introduced for: 0.8, 34, , ., -, NULL, #> [1] "20/20000" NA NA "20/400" "20/2000" "20/50", #> [7] NA NA NA NA, #> 8x NA introduced for: 34, 3/60, 2/200, 20/50, , ., -, NULL, #> [1] "20/20000" "20/25" NA NA NA NA, #> 8x NA introduced for: 0.8, 3/60, 2/200, 20/50, , ., -, NULL, #> [1] "20/20000" NA "20/200" NA NA NA, #> [1] "20/20000" "20/125" NA NA NA NA, ## "plus/minus" entries are converted to the most probable threshold (any spaces allowed), ## or evaluating them as logmar values (each optotype equals 0.02 logmar), ## or you can also decide to completely ignore them (converting them to the nearest snellen value in the VA chart), #> [1] "20/200" "20/20" "20/50" "20/20" "20/32", #> [1] "r" "r" "r" "r" "l" "l" "l" "l" "b" "b", #> [1] "od" "od" "od" "od" "os" "os" "os" "os" "ou" "ou", #> Missing values and/or meaningless strings contained, ## If you are using different strings to code for eyes, e.g., you are using a different language, you can change this either with the "eyestrings" argument, ## or change it more globally with `set_eye_strings`, # to restore the default, call set_eye_strings empty. acuity for the patients are. endobj eyestr was designed with the use in rmarkdown in mind, most explicitly for the use inline. In the meantime, to ensure continued support, we are displaying the site without styles <> <>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> The conversion of Snellen data to logMAR can also be misleading as the abstract and results sections of papers that use this process sometimes give the impression that data have been collected using logMAR charts suggesting the data are more reliable that they actually are. Thus, the authors said, the specific retinal disease state and extent of edema may play a role in the variability between the measurements. Snellen fractions need to be entered with "/". vector of va class. As you can imagine, a lot of those steps rely hugely on reasonable naming of your columns and this is what makes this function unfortunately a bit fragile. Accessibility Clipboard, Search History, and several other advanced features are temporarily unavailable. Bookshelf government site. Calling va() without specifying the to argument will simply clean the visual acuity entries - any notations will be accepted, no plausibility checks yet performed. Vision Research 90: 2-9. To Snellen: It takes an (atomic) vector with visual acuity entries as the only required argument. You can use recodeye for very convenient recoding. In the group of patients, the eyes with the lower visual acuity, and the right eyes of the healthy subjects, were . However, it may be noteworthy to mention the subtle distinction of periods and durations, which are an idiosyncrasy of time measurements and well explained in this thread. hand movement and (no) perception of light, use logMAR ! numeric (for logMAR), or integer (for ETDRS). You are using a browser version with limited support for CSS. Could be etdrs, logmar, snellendec. Prospective evaluation of visual acuity assessment: a comparison of snellen versus ETDRS charts in clinical practice (An AOS Thesis). Of the five conditions evaluateddiabetic retinopathy (DR) with diabetic macular edema (DME), DR without DME, wet age-related macular degeneration (AMD), dry AMD, and retinal vein occlusiononly those eyes that had DR without DME did not show a significant difference between VA scores. plausibility_methods, 2023 Jan 30;59(2):263. doi: 10.3390/medicina59020263. Mean patient age was 62.8 years (range, 25-93 years), and there was a mean of 27.2 days between measurements. NhNxJ*6~+a2""7oPTpc$N0>6o?#',pzz\$B] 2c<NR#F6`+5a'I0w /5ap0EfQa\JMX"2-r$'I;mzL&!D .3aO*3aOI:?tHGdc %gLT"M?npz&~r=e`V1$%#2 notation for qualitative entries is simplified. Since there are 5 letters per line, the total score for a line on the LogMAR chart represents a change of 0.1 log units. Most retrospective reviews convert Snellen visual acuity measurements obtained during routine clinic visits to logarithm of the minimum angle of resolution (logMAR) units so that statistical manipulations can be performed. To Snellen: Internet Explorer). back to Snellen, it is a very natural thing to eye specialists to think Excel spreadsheet picture depicting an example of Snellen VA 6/122 and 6/12+2 with their respective logMAR equivalents. If you have columns with VA or IOP that contain only 0 and 1 for example (which is unlikely, but not impossible), you can just set, Getting the new names based on the indices of the columns, Creating a vector of expected new names for the summary after myopization, Do not use numeric coding for eyes in column names, Separate eye and VA and IOP codes with underscores (bcva_l_preop, VA_r, left_va, IOP_re), Dont use underscores when you dont need to: Consider each section divided by an underscore as a relevant characteristic of your variable. PMC endobj 2023 Jan 19;9:1100241. doi: 10.3389/fmed.2022.1100241. hand movement and (no) perception of light, use logMAR ! 8 0 obj <> <>/PageLabels 249 0 R>> Before 2010. Novel Method for Analyzing Snellen Visual Acuity Measurements. Retina 30 (7). Reference values for these are customizable and can be left as CF, HM, LP and NLP (Appendix S1). Plausibility checks are performed for the automatically or manually defined Accepted VA formats / Plausibility checks Conversion of Snellen visual acuity fractions to approxETDRS letter scores for the purpose of performing statistical manipulations provides more readily interpretable outcomes compared with the current strategy of converting Snellen visual acuity fractions to logMAR units. Tiew, S., Lim, C. & Sivagnanasithiyar, T. Using an excel spreadsheet to convert Snellen visual acuity to LogMAR visual acuity. The ETDRS chart is the chart used most often in clinical research. It will no longer be. Supported by an unrestricted grant from Research to Prevent Blindness, Inc. and National Eye Institute core center grant P30 EY014801 to the University of Miami. difficult to justify a "negative" letter score in a test which only has Snellen to logMAR: logMAR = -1 * log10(snellen_frac) Snellen to ETDRS: ETDRS = 85 + 50 * log10(snellen_frac) Gregori et al.. ETDRS to logMAR: logMAR = -0.02 * etdrs + 1.7 Beck et al. If NULL (default), will simply "clean up" VA entries. A conversion to snellen gives a good gauge of how the visual There is basically a nearly infinite amount of possible combinations of how to enter data, and it is likely that myop will not be able to deal with all of them. Trans Am Ophthalmol Soc. volume34,pages 21482149 (2020)Cite this article. HHS Vulnerability Disclosure, Help Results: A linear relationship exists between true ETDRS letter scores, approxETDRS letter scores, and logMAR units. <> It will remove duplicate rows, and pivot the eye variable to one column and generate a single column for each variable, thus shaping the data for specific types of analysis. equivalent to 0.02 logmar (assuming 5 letters in a row in a chart), NA is assigned to strings such as "." Cleans and converts visual acuity notations (classes) A linear relationship exists between true ETDRS letter scores, approxETDRS letter scores, and logMAR units. Snellen visual acuity measurements were converted to approximate ETDRS (approxETDRS) letter scores for statistical manipulations and then converted back to Snellen equivalent fractions. ETDRS letter, in order to keep it as a measurement (not: NA). Reprint requests: Philip J. Rosenfeld, MD, PhD, Bascom Palmer Eye Institute, 900 NW 17th St., Miami, FL 33136; e-mail: [emailprotected]. <> "etdrs", "logmar" or "snellen" - Please try after some time. The results of this study suggest that for both clinical and research purposes, both Snellen and ETDRS can be used interchangeably. Snellen fractions need to be entered with "/". 2010 Mar;30(2):200-3. doi: 10.1111/j.1475-1313.2009.00700.x. VA chart Depending a lot on how the data was entered, the results could become quite surprising. J Refractive Surg. If smallstep = TRUE, each snellen optotype will be considered The etdrs values for NLP and PL are deliberately set at those values because doi: 10.1016/s0002-9394(02)01825-1, Hand movements and counting fingers are converted following - https://doi.org/10.1167/iovs.05-0981 Plausibility checks are performed for the automatically or manually defined https://doi.org/10.1016/s0002-9394(02)01825-1. integer coding 0:1 and 1:2, right eye being the lower number. Mean value for Snellen Visual Acuity was 0.043 and that of ETDRS was 0.02365 LogMAR. M]D_*zcP?VpON`7?44N]p+8arMa*\ or "", "n/a" or " ". Entries with mixed VA notations Real Life Multicenter Comparison of 24-Month Outcomes of Anti-VEGF Therapy in Diabetic Macular Edema in Turkey: Ranibizumab vs. Aflibercept vs. Ranibizumab-Aflibercept Switch. See Also . Indeed, in my experience R often needs eyes to be in a single column, with each other variable having their own dedicated column. the VA chart are used. snellen_steps, PubMedGoogle Scholar. ContentAdmin Dr. Hermann Snellen's chart standardized vision testing and established a reliable process of diagnosis in its time. You may search for similar articles that contain these same keywords or you may Must be atomic. 1 0 obj acuity for the patients are. Charles RC, Frost NA. 1, 35 The first 4 columns contain VA equivalents as they are currently understood, and the fifth column contains the expected 95% ETDRS CI for each Snellen . Distances between lines were not consistent. <> The ESV-3000 is the only large-format standardized ETDRS testing device. In order to calculate with qualitative entries counting fingers, Snellen to ETDRS: ETDRS = 85 + 50 * log10 (snellen_frac) doi: 10.1097/iae.0b013e3181d87e04 ETDRS to logMAR: logMAR = -0.02 * etdrs + 1.7 Beck et al. It can be rear or front illuminated. ## Mildly messy data frame with several variables spread over two columns: ## the variable has not been exactly named, (but it is probably IOP data), ## you can specify the dimension with the var argument. 2 0 obj Ignored if the value should not be plausible. Examples. eye is dedicated to facilitate ophthalmic research, providing convenient application programming interfaces (API) for common tasks: eye includes a visual acuity conversion chart. Visual acuity testing. Arguments to eyes_to_string are passed via : eyestr will create a string which you can paste into a report. The ESV-3000 allows testing up to 20/200 ETDRS Acuity at a test distance of 4 meters The device is operated by infrared remote control. notation. Its formula is: 100 - 50 x logMAR or 100 + 50 x log (V). Ferris FL, Kassoff A, Bresnick GH, Bailey I. 1 for an example of our spreadsheet. FALSE: [6] The formula used in calculating the score is: Given that each line has 5 optotypes, the equivalent formula is: The LogMAR chart is designed to enable more accurate estimates of acuity as compared to other acuity charts (e.g., the Snellen chart). Kaiser PK. ETDRS letter, in order to keep it as a measurement (not: NA). However, visual acuity measurements expressed as logMAR units are not intuitively interpretable by clinicians. Dutch eye doctor Hermann Snellen developed the Snellen eye chart in the 1860s. A Snellen score of 6/6 (20/20), indicating that an observer can resolve details as small as 1 minute of visual angle, corresponds to a LogMAR of 0 (since the base-10 logarithm of 1 is 0); a Snellen score of 6/12 (20/40), indicating an observer can resolve details as small as 2 minutes of visual angle, corresponds to a LogMAR of 0.3 (since the base-10 logarithm of 2 is near-approximately 0.3), and so on. 2023 Feb 1;9(1):8. doi: 10.1186/s40942-023-00445-0. It is more user friendly, since it avoids decimal values and is more intuitive, since higher values indicate better vision. 3,575,655. If the argument smallstep = TRUE, the entries will be converted to logmar values (0.02 logmar for each optotype). ziXyS*(P9_"H3 PznjpPF"?9a{i\[$1&GPwa1W1"82zrX?7C=BH&LBOI"I`RAk}d Snellen Notation (logMAR to Snellen conversion for 65 letters): 20/50. This notation has long been abandoned for the use of equivalent notations, where the numerator is standardized to a fixed value, regardless of the true viewing distance. Schulze-Bonsel et al. The authors also conducted a subgroup analysis by disease state. notation. endobj eyes offers a very simple tool for counting patients and eyes. In 1982, the chart was renamed the ETDRS chart as it was recommended to be used in the Early Treatment Diabetic Retinopathy Study (note: the terms ETDRS chart and logMAR chart are not interchangeable logMAR is not a type of chart, but rather a term to describe visual acuity notation. The interconversion between Snellen visual acuity measurements, logMAR units, and approxETDRS letter scores was prepared in a tabular form for easy reference. official website and that any information you provide is encrypted set out to compare the variability between the two measurements of best-corrected visual acuity (BCVA). For more information, please refer to our Privacy Policy. VA cleaning Qualitative visual acuity entries [1][3] They described their motivation for designing the LogMAR chart as follows: "We have designed a series of near vision charts in which the typeface, size progression, size range, number of words per row and spacings were chosen in an endeavour to achieve a standardization of the test task.". logMAR to ETDRS: logMAR rounded to the first digit and converted with the visual acuity chart (see section VA chart) Snellen to logMAR: logMAR = -1 * log10(snellen_frac) Snellen to ETDRS: ETDRS = 85 + 50 * log10(snellen_frac) doi: 10.1097/iae.0b013e3181d87e04 ETDRS to logMAR: logMAR = -0.02 * etdrs + 1.7 Proper method for calculating average visual acuity. Fazel F, Malekahmadi M, Feizi A, Oliya B, Tavakoli M, Fazel M. BMC Ophthalmol. In the era of big data, there needs to be an efficient way of tidying up data to facilitate analysis. Outside of the U.S., eye doctors may use a logMAR visual scale or a similar scale to the Snellen visual chart in which they measure vision in . PURPOSE: To develop a computerized method of visual acuity testing for clinical research as an alternative to the standard Early Treatment for Diabetic Retinopathy Study (ETDRS) testing protocol,. ?myop for help, #> From etdrs. This, again, requires a certain format of names and codes - See Names and Codes. males. unambiguous value to visual acuity, with non-arbitrary thresholds based on psychometric functions. You can find with eye:::va_chart. Snellen-Logmar Calculator. Correspondence to The Snellen visual acuity notation was developed by Hermann Snellen in 1862, during the time of the Civil War. This overrides the smallstep argument. The development of a record logMAR visual acuity chart for use in routine clinical practice. 5 0 obj Because the standard testing . <> Bailey and Lovie created their own modified version of the Snellen chart to reduce some of its inaccuracies. Other patents pending. in Snellen. We present an excel spreadsheet formula to convert Snellen visual acuity to logMAR acuity. PubMed Central You can get creative with your snellens. [ 14 0 R] See also "VA classes", logMAR to ETDRS: logMAR rounded to the first digit and converted with Schulze-Bonsel et al. Therefore, we recommend the following for data entry in excel. endobj ISSN 1476-5454 (online) An important step in eyes is the guessing of the columns that identify patients and eyes. When VA was assessed by subgroups, eyes with worse vision had a greater difference between Snellen and ETDRS scores: Eyes 20/25 or better were a mean +1.9 letters better on ETDRS testing, and eyes 20/160 or worse were a mean +12.6 letters better on ETDRS testing (p < .05 for both). The site is secure. Will find the eye column, unify the codes for the eyes (all to r and l) and pivot the columns wide, that have been specified in cols. considered an exact science and any attempt to use formulas will result Gregori, Ninel Z MD*; Feuer, William MS*; Rosenfeld, Philip J MD, PhD*. Three out of 5 optotypes per line had to be correctly identified, while wrong answers were monitored. In this case, the argument var will be used to name the resulting variable. It is very will force to evaluate from which notation to convert - Must be doi: 10.1097/iae.0b013e3181d87e04, ETDRS to logMAR: logMAR = -0.02 * etdrs + 1.7 Effect of letter separation on computerised visual acuity measurements: comparison with the gold standard Early Treatment Diabetic Retinopathy Study (ETDRS) chart. Mean Snellen VA was 0.40 logMAR (20/50 Snellen equivalent), and mean ETDRS measurement was 0.27 logMAR (20/40 Snellen equivalent). Data is temporarily unavailable. Yet, I believe that the approach is still better than just omitting the letters or (worse) assigning a missing value to those entries. To which Snellen notation to convert: "m", "dec" or "ft", how +/- entries are evaluated. Have a thought about this article? These conversions were done via our excel spreadsheet formula taking into account methods from our literature searches. plus and minus from Snellen entries are converted: if entry -2 to +2 : take same Snellen value, if < -2 : take Snellen value one line below. and transmitted securely. Cleans and converts visual acuity notations (classes) The user can specify the original VA notation, but va will check that and ignore the argument if implausible. "etdrs", "logmar", "snellen" or "snellendec". ), DETECT THE HIDDEN DANGER OFTHYROID EYE DISEASE (TED), 2022 Horizon Therapeutics plc DA-UNBR-US-01273 12/22, VA Variability: Snellen Versus ETDRS Outcomes, Instruction Courses and Skills Transfer Labs, Program Participant and Faculty Guidelines, LEO Continuing Education Recognition Award, What Practices Are Saying About the Registry, Provider Enrollment, Chain and Ownership System (PECOS), Subspecialty/Specialized Interest Society Directory, Subspecialty/Specialized Interest Society Meetings, Minority Ophthalmology Mentoring Campaign, Global Programs and Resources for National Societies, Dr. Richard Mills' Opinions, 2002 to 2016, International Society of Refractive Surgery. Notation for qualitative entries is simplified (NPL becomes NLP, PL becomes LP). Allows conversion of CF, HM, LP and NLP into LogMAR. Overall, 76.6% of eyes correctly identified more letters with the ETDRS chart. 14 0 obj <> Article sharing sensitive information, make sure youre on a federal va_mixed(), difficult to justify a "negative" letter score in a test which only has The mean BCVA in decimal notation was 0.970.15 and 0.970.18 with the Snellen and ETDRS charts, respectively (P =0.78). Calculate from Logmar to Snellen. Roser DA, Laidlaw DAH, Murdoch IE. may email you for journal alerts and information, but is committed <> Our data set consists of 100 patients who underwent corneal collagen cross linking. This is based on the assumption of 5 optotypes in a row. 2009;107:31124. Firstly, each letter was scored using linear interpolation. - https://doi.org/10.1167/iovs.05-0981, (No) light perception are converted following the suggestions by 2023 Jan 27;23(1):40. doi: 10.1186/s12886-023-02790-y. . Some error has occurred while processing your request. In ETDRS charts, the Sloan letters are used (Sloan letters are perfectly square approximately equally legible one from another), while the BaileyLovie chart used rectangular (5:4) letters based on the Transport typeface, as set out in British Standard 4274:1968.[1]. <. Letter Score logMAR Snellen Equivaent 0-3 1.70-1.64 <20/800 4 to 8 1.62-1.54 20/800 9 to 13 1.52-1.44 20/640 14 to 18 1.42-1.34 20/500 Br J Ophthalmol. means, it can also be a character vector), Qualitative must be either of PL, LP, NLP, NPL, HM, CF (any case allowed). [4], The chart was designed by Ian Bailey[5] and Jan E. Lovie-Kitchin at the National Vision Research Institute of Australia. BCVA Unable to load your collection due to an error, Unable to load your delegates due to an error. The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Kaiser [4] described how he prepared for statistical analysis by converting the Snellen fraction to logMAR. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in myop will work reliably if you adhere to the following: An exception is when there is only one column for each eye. We converted all the Snellen visual acuities to logMAR visual acuities. Zero LogMAR indicates standard vision, positive values indicates poor vision, and negative values indicates good vision. You are using a browser version with limited support for CSS. An official website of the United States government. FALSE: Snellen visual acuity measurements were converted to approximate ETDRS (approxETDRS) letter scores for statistical manipulations and then converted back to Snellen equivalent fractions. In a retrospective chart review, Yu et al. However, LogMAR is actually a notation of vision loss. logMAR to ETDRS: logMAR rounded to the first digit and converted with the visual acuity chart (see section VA chart) Snellen to logMAR: logMAR = -1 * log10 (snellen_frac) Snellen to ETDRS: ETDRS = 85 + 50 * log10 (snellen_frac) 10.1097/iae.0b013e3181d87e04 ETDRS to logMAR: logMAR = -0.02 * etdrs + 1.7 Beck et al. Elsevier BV: 194205. A linear relationship exists between true ETDRS letter scores, approxETDRS letter scores, and logMAR units. Provided by the Springer Nature SharedIt content-sharing initiative, International Journal of Retina and Vitreous (2022), Eye (Eye) According to The New York Times, he asked Dr. Snellen to make the chart. Each class can be converted from one to another. reveal() takes the grouping argument by and it returns vector for atomic vectors or a data frame for lists. The Snellen chart, which dates back to 1862, is also commonly used to estimate visual acuity. Outcome measures included absolute VA and VA variability among disease states. However, back-conversion should not be 19 0 obj Michael Bach. in very weird Snellen values that have no correspondence to common charts. equivalent to 0.02 logmar (assuming 5 letters in a row in a chart), NA is assigned to strings such as "." CAS Schulze-Bonsel, Kilian, Nicolas Feltgen, Hermann Burau, Lutz Hansen, and Michael Bach. Read reviews, compare customer ratings, see screenshots and learn more about Visual Acuity. Visual Acuity Reporting in Clinical Research Publications. Value blink() is more than just a wrapper around myop(), eyes(), va() and reveal(). 1) hence reducing risk of transcription errors. See also "VA classes", logMAR to ETDRS: logMAR rounded to the first digit and converted with Therefore, Snellen matching the nearest ETDRS and logMAR value in The etdrs values for NLP and PL are deliberately set at those values because %PDF-1.5 endobj notation for qualitative entries is simplified. 15 0 obj You don't have permission to access this content. I do not assume responsability for your data or analysis. The cols argument takes a tidyselection. National Library of Medicine The authors declare no competing interests. and it has internal reasons that make conversion easier. doi: 10.1016/s0002-9394(02)01825-1Beck et al., and Asia Pac J Ophthalmol (Phila). Google Scholar. To help those who are using the standard Snellen chart in their practice and wish to convert it to LogMAR, we have produced 81 possible combinations of Snellen visual acuity and their true. 2001;85:4326. If there still are variables spread over two columns for right and left eyes, then this is an example of messy data. Thank you for visiting nature.com. endobj The ESV-3000 is designed specifically for clinical trials where large-format ETDRS testing (up to 20/200) is performed at 4 meters. This chart is included in the package as va_chart. If a subject can read a line at 20 feet and the "normal" observer can see the same line at 40 feet, then the subject has 20/40 Snellen acuity. Although there seems to be no good statistical reason to convert https://doi.org/10.1167/iovs.05-0981. Federal government websites often end in .gov or .mil. endobj The basic principle of tidy data is: one column for each dimension and one row for each observation. When using a LogMAR chart, visual acuity is scored with reference to the logarithm of the minimum angle of resolution, as the chart's name suggests. Snellen are unfortunately often entered with +/-, which is a violation of psychophysical methods designed to assign one (!) doi: 10.1016/s0002-9394 (02)01825-1 Hand movements and counting fingers are converted following Schulze-Bonsel et al. A more intuitive approach is presented here which uses the conversion of Snellen visual acuity fractions to Early Treatment Diabetic Retinopathy Study (ETDRS) letter scores for statistical manipulations. 7 0 obj ), logMAR and ETDRS. Christina Lim. They found that the ETDRS visual acuity scores were significantly betterand that the difference was more pronounced among eyes with worse visual acuity. Ophthalmic Physiol Opt. Must be atomic. The Apple iPod Touch (Figure 2), communicating with the EVA PC via Wi-Fi, provides . back to Snellen, it is a very natural thing to eye specialists to think Disclaimer. Donders diagnosed vision problems by asking people to look at a chart on a wall and tell him what they could see. Gregori et al.doi: 10.1097/iae.0b013e3181d87e04. Table: Different notations of visual acuity values as decimal values, Snellen fractions, MAR and LogMAR. ## `eye` won't be able to recognize IOP and VA columns, ## But `eye` will fail to understand those variable names, #> eye surgery var mean sd n min max, #> 1 left SLT iop_preop 34.0 NA 1 34 34, #> 2 left SLT iop_postop 14.0 NA 1 14 14, #> 3 left SLT va_preop 44.0 NA 1 44 44, #> 4 left SLT va_postop 48.0 NA 1 48 48, #> 5 right SLT iop_preop 23.5 0.7 2 23 24, #> 6 right SLT iop_postop 13.5 0.7 2 13 14, #> 7 right SLT va_preop 43.5 0.7 2 43 44, #> 8 right SLT va_postop 47.5 0.7 2 47 48, #> 9 left TE iop_preop 32.0 1.0 3 31 33, #> 10 left TE iop_postop 12.0 1.0 3 11 13, #> 11 left TE va_preop 42.0 1.0 3 41 43, #> 12 left TE va_postop 46.0 1.0 3 45 47, #> 13 right TE iop_preop 21.5 0.7 2 21 22, #> 14 right TE iop_postop 11.5 0.7 2 11 12, #> 15 right TE va_preop 41.5 0.7 2 41 42, #> 16 right TE va_postop 45.5 0.7 2 45 46, ## If no second date given, the age today, ## If the second argument is specified, the age until then, https://doi.org/10.1016/s0002-9394(02)01825-1, https://doi.org/10.1097/iae.0b013e3181d87e04, https://doi.org/10.1016/j.jcrs.2004.01.014.