See Fig. 8,425,040; 8,550,631; 10,244,938; and 10,182,713. 1997;13:38891. This is based on the assumption of 5 optotypes in a row. To which class to convert. Internet Explorer). The site is secure. Bethesda, MD 20894, Web Policies <>
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. The notation will be detected automatically and converted to the desired notation. ISSN 0950-222X (print), Using an excel spreadsheet to convert Snellen visual acuity to LogMAR visual acuity, https://doi.org/10.1038/s41433-020-0783-6, Three-dimensional heads-up system assisted pars plana vitrectomy and subretinal recombinant tissue plasminogen activator injection for submacular hemorrhage, Anatomical and functional outcomes of retinal detachment associated with nontraumatic giant retinal tears compared to simple rhegmatogenous retinal detachment, Stabilization of refractive error and associated factors following small incision phacoemulsification cataract surgery, Effect of time to operative repair within twenty-four hours on visual acuity outcomes for open globe injuries, Comment on: Conversion of Snellen visual acuity to LogMAR visual acuity. endobj
Gregori et al.doi: 10.1097/iae.0b013e3181d87e04. PubMed Central integer coding 0:1 and 1:2, right eye being the lower number. It will no longer be. a specific range (0-100). Conversion tables and calculators exist online which allows for whole Snellen fractions to be converted into logMAR equivalents. males. Your message has been successfully sent to your colleague. Read reviews, compare customer ratings, see screenshots and learn more about Visual Acuity. This can compromise data quality and accuracy of outcomes. The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). snellen_steps, In a retrospective chart review, Yu et al. Prospective evaluation of visual acuity assessment: a comparison of snellen versus ETDRS charts in clinical practice (An AOS Thesis). Trabelsi O, Bouladi M, Ouertani A, Trabelsi A. Clin Ophthalmol. This overrides the smallstep argument. Indeed, in my experience R often needs eyes to be in a single column, with each other variable having their own dedicated column. eyestr was designed with the use in rmarkdown in mind, most explicitly for the use inline. The value of each letter was calculated by dividing. For more information, please refer to our Privacy Policy. He was a colleague of Dr. Franciscus Donders. Cleans and converts visual acuity notations (classes) Description Then the column names can consist of eye strings only. Holladay et al.doi: 10.1016/j.jcrs.2004.01.014, Beck et al. & Tm. Snellen decimal ETDRS Letters Snellen feet Snellen meter logMAR 2.00 100 20/10 6/3 -0.3 1.60 95 20/12.5 6/4 -0.2 1.25 90 20/16 6/5 -0.1 1.00 85 20/20 6/6 0 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 Gregori, Ninel Z MD*; Feuer, William MS*; Rosenfeld, Philip J MD, PhD*. convertVA returns a vector of three classes: One of snellen, snellendec, logmar, etdrs or quali. Therefore, Snellen matching the nearest ETDRS and logMAR value in in very weird Snellen values that have no correspondence to common charts. 3 0 obj
The World Health Organization established criteria for low vision using the LogMAR scale. modify the keyword list to augment your search. It will return a list object which gives you easy access to the data. va_mixed(), The authors declare that they have no conflict of interest. unambiguous value to visual acuity, with non-arbitrary thresholds based on psychometric functions. This overrides the smallstep argument. An official website of the United States government. BCVA 10.1016/s0002-9394 (02)01825-1 Unable to load your collection due to an error, Unable to load your delegates due to an error. Although kind of nice, blink is more a nerdy extra and is not likely to be used much. volume34,pages 21482149 (2020)Cite this article. <>
ETDRS letter, in order to keep it as a measurement (not: NA). right eyes: c(r, re, od, right) and, left eyes: c(l, le, os, left) and, both eyes: c(b, both, ou), Next, it will look for columns that are plainly called ID, Last, it will search for all names that contain either pat or id, columns will full string eye or eyes will be given precedence, right eyes: c(r, re, od, right), left eyes: c(l, le, os, left), Re-arranging and recoding substrings in a way that strings for eyes always appear at first position. We converted all the Snellen visual acuities to logMAR visual acuities. See also "VA classes", logMAR to ETDRS: logMAR rounded to the first digit and converted with Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To Snellen: endobj
Ophthalmic Physiol Opt. 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) Methods: For example, eight columns that store data of four variables for right and left eyes will be pivoted to 5 columns (one eye column and four further variable columns)). - https://doi.org/10.1167/iovs.05-0981 For access, try logging in If you are subscribed to this group and have noticed abuse, report abusive group. Mean patient age was 62.8 years (range, 25-93 years), and there was a mean of 27.2 days between measurements. Please try again soon. I personally find starts_with, ends_with, contains() or the more general matches() very useful. 2023 Jan 27;23(1):40. doi: 10.1186/s12886-023-02790-y. From the laboratory to the clinic. Charles RC, Frost NA. Snellen fractions need to be entered with "/". This chart and VA conversion formulas are based on charts in Kaiser [4] described how he prepared for statistical analysis by converting the Snellen fraction to logMAR. Snellen visual acuity measurements were converted to approximate ETDRS (approxETDRS) letter scores for statistical manipulations and then converted back to Snellen equivalent fractions. 2014 Sep-Oct;3(5):277-85. doi: 10.1097/APO.0000000000000007. FALSE: 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. which_va(). Methods: Snellen visual acuity measurements were converted to approximate ETDRS (approxETDRS) letter scores for statistical manipulations and then converted back to Snellen equivalent fractions. Department of Ophthalmology, University Hospitals of Leicester NHS Trust, Infirmary Square, Leicester, LE1 5WW, UK, Christina Lim,Ian De Silva&Stephenie Tiew, You can also search for this author in Schulze-Bonsel et al. You can read the full text of this article if you: Keywords
The Apple iPod Touch (Figure 2), communicating with the EVA PC via Wi-Fi, provides . see "Examples", ETDRS must be integer-equivalent between 0 and 100 (integer equivalent blink() is more than just a wrapper around myop(), eyes(), va() and reveal(). For more information on customizing the embed code, read Embedding Snippets. [1] Each line of the LogMAR chart comprises the same number of test letters (effectively standardizing the test across letter size); the letter size change from one line to the next is a constant ratio, as is the spacing between lines (making the chart easy to use at nonstandard viewing distances). There was complete correlation between the manual conversion and excel spreadsheet formula. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Because the standard testing . Snellen fractions (meter/ feet) need to be entered as fraction with 8600 Rockville Pike Therefore I decided to stop the work on it. Kucukevcilioglu M, Yeilta YS, Durukan AH, Unlu N, Onen M, Alp MN, Kalayci D, Acar MA, Sekeroglu MA, Citirik M, Altintas AGK, Hazirolan D, Ozdal PC, Toklu Y, Bicer T, Ugurlu N, Budakoglu O, Yazar Z, Zeki NIU, Serdar K, Doguizi S, Erol YO, Atilgan CU, Yorgun MA, Soba DO, Berker N, Baskan C. Medicina (Kaunas). "etdrs", "logmar", "snellen" or "snellendec". 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) Either of character (for Snellen, snellendec, and qualitative), 5715 W. Howard Street, Niles, IL, 60714 USA 19 0 obj
ETDRS charts (within about 2% of the letter size at each logMAR level). Internet Explorer). Bailey IL, Lovie JE (2013). PubMedGoogle Scholar. Publishers note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. The results of this study suggest that for both clinical and research purposes, both Snellen and ETDRS can be used interchangeably. VA cleaning reveal() is basically a slightly complicated wrapper around mean(), sd(), length(), min() and max() (with na.rm = TRUE and length() counting only non-NA values). equivalent to 0.02 logmar (assuming 5 letters in a row in a chart), NA is assigned to strings such as "." snellen fraction. See also "VA classes", logMAR to ETDRS: logMAR rounded to the first digit and converted with 2010 Mar;30(2):200-3. doi: 10.1111/j.1475-1313.2009.00700.x. <>
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. As for myop and of course blink, a specific column naming is required for a reliable automatic detection of patient and eye column(s) ( see Names and codes). #> Unclear which is the eye column. This may be a necessary data formal for specific questions. This is a common misconception). 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. If smallstep = TRUE, each snellen optotype will be considered 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. You can use recodeye for very convenient recoding. 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. All told, 413 patients (773 eyes) met the inclusion criteria for this study. The interconversion between Snellen visual acuity measurements, logMAR units, and approxETDRS letter scores was prepared in a tabular form for easy reference. doi: 10.1016/s0002-9394(02)01825-1Beck et al., and If NULL (default), will simply "clean up" VA entries. endobj
## `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. The mean and range of testing times were: ETDRS 34.65 (9.38-80.18) seconds, cRLM 21.17 (5-40) seconds, Snellen 18.67 (3-35.56) seconds. It is very vector of va class. 13 0 obj
## automatic detection of VA notation and converting to logMAR by default, #> [1] "20/320" "20/80" "20/32" "20/70", ## And the decimal snellen notation, so much loved in Germany, ## Remove weird entries and implausible entries depending on the VA choice, #> From snellen. in Snellen. The score was further modified by adding/subtracting 0.02 logMAR to converted values for letters correctly/incorrectly identified on previous/next line. The test-retest variability of the charts was similar, with the 95% tolerance limit for change being +/-0.14 logMAR for ETDRS, +/-0.16 for reduced logMAR and +/-0.18 for Snellen. Plausibility checks are performed for the automatically or manually defined Snellen Notation (logMAR to Snellen conversion for 65 letters): 20/50. However, additional letters read or missed letters are not accounted for. Other patents pending. Their revised chart included the same amount of letters on each line, a standardization of legibility, and equidistant rows, to name just a few adjustments. they are unlikely to happen by chance as a wrong entry (and as integers), 5 0 obj
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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. notation for qualitative entries is simplified. In order to calculate with qualitative entries counting fingers, 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. increase/decrease Snellen fractions by lines. By default, plus/minus entries are evaluated as intended by the 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. Roser DA, Laidlaw DAH, Murdoch IE. VA conversion You may search for similar articles that contain these same keywords or you may
Visual acuity is a vital outcome measure in determining efficacy of treatments and interventions in ophthalmology. vector of va class. However, if you adhere to the naming conventions, blink (and myop) will do a great job for you. <>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>>
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Rosser et al. It is very You have full access to this article via your institution. . doi: 10.1016/s0002-9394 (02)01825-1 Hand movements and counting fingers are converted following Schulze-Bonsel et al. You can find with eye:::va_chart. 2010. Novel Method for Analyzing Snellen Visual Acuity Measurements. Retina 30 (7). va() will detect the class automatically based on specific rules detailed below. Please enable scripts and reload this page. convertVA returns a vector of three classes: One of snellen, snellendec, logmar, etdrs or quali. 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. Have a thought about this article? Three out of 5 optotypes per line had to be correctly identified, while wrong answers were monitored. endobj
doi: 10.1016/s0002-9394(02)01825-1, Hand movements and counting fingers are converted following Pesky visual acuity notations are now a matter of the past. Holladay J. Charts with the Snellen E and the Landolt C (Precision Vision) which mimic the ETDRS charts were used to assess visual acuity. "etdrs", "logmar" or "snellen" - It is more user friendly, since it avoids decimal values and is more intuitive, since higher values indicate better vision. Depending a lot on how the data was entered, the results could become quite surprising. By default, plus/minus entries are evaluated as intended by the endobj
official website and that any information you provide is encrypted or "", "n/a" or " ". Mean Snellen VA was 0.40 logMAR (20/50 Snellen equivalent), and mean ETDRS measurement was 0.27 logMAR (20/40 Snellen equivalent). Value https://doi.org/10.1016/j.jcrs.2004.01.014. The authors have no commercial or proprietary interest in any product or corporation mentioned in this article. Again, good names and tidy data always help! reveal() takes the grouping argument by and it returns vector for atomic vectors or a data frame for lists. increase/decrease Snellen fractions by lines. Please always check the result for plausibility. The ETDRS chart is fully accessible on modern computerized vision testing systems, thanks to Dr. Bailey and Dr. Lovies work to create a more accurate chart! doi: 10.1016/s0002-9394 (02)01825-1 Hand movements and counting fingers are converted following Schulze-Bonsel et al. considered an exact science and any attempt to use formulas will result Out of convenience, data is often entered in a wide format: In eye research, there will be often two columns for the same variable, one column for each eye. any case allowed. Vision Research 90: 2-9. The https:// ensures that you are connecting to the In this case, the argument var will be used to name the resulting variable. <>
Although there seems to be no good statistical reason to convert You can also decide to simply clean your VA vector with cleanVA(x). https://doi.org/10.1097/iae.0b013e3181d87e04. Zero LogMAR indicates standard vision, positive values indicates poor vision, and negative values indicates good vision. Conversion from Snellen to Logmar | Print | The Snellen Chart, which traditionally has been used to measure visual acuity, is easily recognised as one of the hallmarks of the ophthalmologist's consulting room. <>
in Snellen. Table: Different notations of visual acuity values as decimal values, Snellen fractions, MAR and LogMAR. In the era of big data, there needs to be an efficient way of tidying up data to facilitate analysis. #> maintained, but will be kept in the package. Data is temporarily unavailable. You can change the way numbers are converted to english with the english argument. ## If the dimension is already part of the column names, this is not necessary. To which Snellen notation to convert: "m", "dec" or "ft", how +/- entries are evaluated. VA classes Read about tidyselection. ), 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. 2023 Jan 30;59(2):263. doi: 10.3390/medicina59020263. Proper method for calculating average visual acuity. It can be rear or front illuminated. Results: 12 0 obj
Specific types of logMAR chart include the original Bailey-Lovie chart,[3] as well as the ETDRS charts, developed for the Early Treatment Diabetic Retinopathy Study. and JavaScript. Beck et al. doi: 10.1097/iae.0b013e3181d87e04, ETDRS to logMAR: logMAR = -0.02 * etdrs + 1.7 2023 M&S Technologies #> # with 3 more variables: l_iop_postop , l_va_preop , #> The lifecycle of blink() has expired. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. We measured their vision pre and post cross linking. All Snellen and ETDRS VA measurements were converted to logMAR units for direct comparison, and the variability between measurements was calculated. See names and codes If there is already a column called eye or eyes, myop will not make any changes - because the data is then already assumed to be in long format. M]D_*zcP?VpON`7?44N]p+8arMa*\ Unauthorized use of these marks is strictly prohibited. Coney JM, Zubricky R, Sinha SB, Sonbolian N, Zhou L, Hull TP, Lewis SA, Miller DG, Novak MA, Pendergast SD, Pham H, Platt SM, Rao LJ, Schartman JP, Singerman LJ, Donkor R, Fink M, McCoy J, Karcher H. Int J Retina Vitreous. This chart is included in the package as va_chart. Accepted VA formats / Plausibility checks . The ETDRS chart is the chart used most often in clinical research. 2009 Dec;107:311-24. stream
This site needs JavaScript to work properly. This chart and VA conversion formulas are based on charts in doi: 10.1097/iae.0b013e3181d87e04, ETDRS to logMAR: logMAR = -0.02 * etdrs + 1.7 Short-Term Total Tamponade with Perfluorocarbon Liquid and Silicone Oil in Complex Rhegmatogenous Retinal Detachment with Severe Proliferative Vitreoretinopathy. Efficacy of small-incision lenticule extraction surgery in high astigmatism: A meta-analysis. Distances between lines were not consistent. Reshaping many such columns can be a daunting task, and myop() makes this easier. You can capitalise the first number with the caps argument. ignoring plus/minus entries and just returning the FOIA The etdrs values for NLP and PL are deliberately set at those values because ETDRS letter, in order to keep it as a measurement (not: NA). snellen_steps, https://doi.org/10.1167/iovs.05-0981. Elsevier BV: 194205. This is a simple function and should not require much explanation. Snellen are unfortunately often entered with +/-, which is a violation of psychophysical methods designed to assign one (!) Allows conversion of CF, HM, LP and NLP into LogMAR. endobj
Michael Bach. #> blink , #> Data , #> , #> 1 a right TE 21 11 0.88 0.80, #> 2 a left TE 31 11 0.88 0.80, #> 3 b right TE 22 12 0.86 0.78, #> 4 b left TE 32 12 0.86 0.78, #> 5 c right SLT 23 13 0.84 0.76, #> 6 c left TE 33 13 0.84 0.76, #> 7 d right SLT 24 14 0.82 0.74, #> 8 d left SLT 34 14 0.82 0.74, #> Count of patient and eyes , #> Counts , #> Visual acuity , #> Intraocular pressure , #> $IOP_eyes (right and left eyes), #> Warning: Data seems already myopic - no changes made. - https://doi.org/10.1167/iovs.05-0981 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,. (Also see related commentary by Andrew P. Schachat, MD, and Marco A. Zarbin, MD, in the same issue. This is intended for integration into rmarkdown reports, or for easy copy / pasting. the VA chart are used. P30 EY014801/EY/NEI NIH HHS/United States. The mean reading times for the subjects were 34.65 s for ETDRS, 21.17 s for reduced logMAR and 18.67 s for Snellen. The same outcomes (in Snellen fractions) were obtained with statistical manipulation of either approxETDRS letter scores or logMAR conversions. Outcome measures included absolute VA and VA variability among disease states. 1 0 obj
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[4], The chart was designed by Ian Bailey[5] and Jan E. Lovie-Kitchin at the National Vision Research Institute of Australia. Snellen acuity is given in terms of a Snellen fraction S, which is defined as Typical testing distances for the Snellen chart are 20 feet and 6 meters. Firstly, each letter was scored using linear interpolation. Ferris FL, Kassoff A, Bresnick GH, Bailey I. Therefore, transforming +/- notation to actual results is in itself problematic and the below suggestion to convert it will remain an approximation to the most likely true result. and JavaScript. va_mixed(), The "ETDRS" chart is another vision chart that is often used for ophthalmic studies as it is easy to convert the letters on this chart for statistical values to help better understand published results. For example, in Peden et al., Snellen VAs were retrospectively collected from records and converted to letter values 'in a standard fashion for statistical analy-sis'.12 Graphs misleadingly include Y-axes of 'ETDRS let-ters' with gure 5 scores averaging around 60 letters (0.50 logMAR, Snellen 6/18, 20/60), whereas the patient has J Refractive Surg. <>
The ESV-3000 is the only large-format standardized ETDRS testing device. 2006. Visual Acuities Hand Motion and Counting Fingers Can Be Quantified with the Freiburg Visual Acuity Test. Investigative Ophthalmology & Visual Science 47 (3): 123640. ## But which dimension of "r"/"l" are we exactly looking at? Calculate from Logmar to Snellen. However, eye is also variable (a dimension of your observation), and it can also be stored in a separate column. Purpose: #> id eye surgery iop_preop iop_postop va_preop va_postop, #> , #> 1 a right TE 21 11 41 45, #> 2 a left TE 31 11 41 45, #> 3 b right TE 22 12 42 46, #> 4 b left TE 32 12 42 46, #> 5 c right SLT 23 13 43 47, #> 6 c left TE 33 13 43 47, #> 7 d right SLT 24 14 44 48, #> 8 d left SLT 34 14 44 48, #> id surgery r_iop_preop r_iop_postop r_va_preop r_va_postop l_iop_preop, #> , #> 1 a TE 21 11 41 45 31, #> 2 b TE 22 12 42 46 32, #> 3 c SLT 23 13 43 47 , #> 4 c TE 33, #> 5 d SLT 24 14 44 48 34. 10 0 obj
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. "/". the VA chart are used. Holladay et al.doi: 10.1016/j.jcrs.2004.01.014, Beck et al. Careers. to maintaining your privacy and will not share your personal information without
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. Or, arguably more appropriate in R, character coding for a categorical variable: you can change those codes with set_eye_strings().