It will be left in the package as such. Publishers note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. An official website of the United States government. va_mixed(), A conversion to snellen gives a good gauge of how the visual For entries with mixed notation, use va_mixed instead. ContentAdmin Dr. Hermann Snellen's chart standardized vision testing and established a reliable process of diagnosis in its time. However, you need to be very careful in those cases if resulting data frame is plausible. Decimal Snellen fractions MAR LogMAR 6m 5m 4m 3m 20ft 10ft 0.010 6/600 5/500 4/400 3/300 20/2000 10/1000 100 2.0 0.012 6/480 5/400 4/320 3/240 20/1600 10/800 80 1.92 There was complete correlation between the manual conversion and excel spreadsheet formula. M]D_*zcP?VpON`7?44N]p+8arMa*\ va_methods, The same outcomes (in Snellen fractions) were obtained with statistical manipulation of either approxETDRS letter scores or logMAR conversions. 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. From the laboratory to the clinic. A conversion to snellen gives a good gauge of how the visual Value Bailey and Lovie created their own modified version of the Snellen chart to reduce some of its inaccuracies. The Snellen chart, which dates back to 1862, is also commonly used to estimate visual acuity. The basic principle of tidy data is: one column for each dimension and one row for each observation. Conversion from Snellen to Logmar - orthoptics.ie PDF Visual Acuity Testing Procedures Manual - Jaeb 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. 2017 Jun 1;135(6):651-653. doi: 10.1001/jamaophthalmol.2017.0932. 16 0 obj Conversions Between Letter, LogMAR, and Snellen Visual Acuity Scores To Snellen: The development of a record logMAR visual acuity chart for use in routine clinical practice. between Snellen (decimal, meter and feet), ETDRS, and logMAR. and JavaScript. FALSE: - https://doi.org/10.1167/iovs.05-0981, (No) light perception are converted following the suggestions by 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. The formula is subsequently validated with manual conversion by two independent clinicians (CL and TS). Snellen-Logmar Calculator. 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. Read reviews, compare customer ratings, see screenshots and learn more about Visual Acuity. Gregori et al.doi: 10.1097/iae.0b013e3181d87e04. Because the standard testing . will force to evaluate from which notation to convert - Must be Qualitative visual acuity lower than counting fingers is assigned 0 endobj plausibility_methods, 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. Holladay J. 15 0 obj means, it can also be a character vector), Qualitative must be either of PL, LP, NLP, NPL, HM, CF (any case allowed). LogMAR chart - Wikipedia Contact Us and let us know. We present an excel spreadsheet formula to convert Snellen visual acuity to logMAR acuity. endobj See also "VA classes", logMAR to ETDRS: logMAR rounded to the first digit and converted with <> It will look for VA and for IOP columns and provide the summary stats for the entire cohort and for right and left eyes for each VA and IOP variable. In the group of patients, the eyes with the lower visual acuity, and the right eyes of the healthy subjects, were . 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 PDF Comparison of static visual acuity between Snellen and Early treatment Those are removed because they are likely categorical codes. 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. Conversion tables and calculators exist online which allows for whole Snellen fractions to be converted into logMAR equivalents. 1 0 obj Dutch eye doctor Hermann Snellen developed the Snellen eye chart in the 1860s. ISSN 0950-222X (print), https://doi.org/10.1038/s41433-021-01764-y, Comment on: Conversion of Snellen visual acuity to LogMAR visual acuity. vector of va class. Please enable scripts and reload this page. doi: 10.1016/s0002-9394(02)01825-1Beck et al., and means, it can also be a character vector), Qualitative must be either of PL, LP, NLP, NPL, HM, CF (any case allowed). The authors also conducted a subgroup analysis by disease state. To which class to convert. convertVA returns a vector of three classes: One of snellen, snellendec, logmar, etdrs or quali. the VA chart are used. Gregori, Ninel Z MD*; Feuer, William MS*; Rosenfeld, Philip J MD, PhD*. By default, numbers smaller than or equal to 12 will be real English, all other numbers will be numbers. 8 0 obj Qualitative visual acuity entries 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. acuity for the patients are. 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. [4], The chart was designed by Ian Bailey[5] and Jan E. Lovie-Kitchin at the National Vision Research Institute of Australia. 17 0 obj 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) endstream The formula to convert Snellen visual acuity measurements to approxETDRS letter scores is 85 + 50 log (Snellen fraction), which may be rounded to the nearest letter. Conversion directly from one cell of Snellen fraction into another cell without manipulation or re-formatting of the original Snellen fraction (Fig. Snellen fractions (meter/ feet) need to be entered as fraction with acuity for the patients are. government site. Asia Pac J Ophthalmol (Phila). Please always keep a critical mind when working with data - if you do get results that seem implausible, there may be a chance that the data is in an unfortunate shape for which eye may not be suitable. The good (logMAR), the bad (Snellen) and the ugly (BCVA, number of your express consent. 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 doi: 10.1016/s0002-9394(02)01825-1, Hand movements and counting fingers are converted following Trans Am Ophthalmol Soc. This site needs JavaScript to work properly. Comparison of the ETDRS logMAR, 'compact reduced logMar' and Snellen eyes also include a convenience function to turn the count into a text. This can compromise data quality and accuracy of outcomes. 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). 13 0 obj 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 Indeed, in my experience R often needs eyes to be in a single column, with each other variable having their own dedicated column. Ovid Technologies (Wolters Kluwer Health): 104650. Therefore, Snellen matching the nearest ETDRS and logMAR value in proposed the line scoring method [3]. Therefore, Snellen matching the nearest ETDRS and logMAR value in For counting eyes, eyes need to be coded in commonly used ways. va function - RDocumentation similar and uniform legibility of each line and offer an ease of conversion of VA to a logarithmic scale. [Landolt C and snellen e acuity: differences in strabismus - PubMed Google Scholar. You may be trying to access this site from a secured browser on the server. Next convert the metric distance to a foot equivalent. Outcome measures included absolute VA and VA variability among disease states. [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). TRUE: plus/minus 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) https://doi.org/10.1016/j.jcrs.2004.01.014. To which Snellen notation to convert: "m", "dec" or "ft", how +/- entries are evaluated. Conversion of Snellen visual acuity to LogMAR visual acuity. 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! BCVA This will remove all entries that are certainly no VA. va() (and of course, its wrappers) cleans and converts visual acuity notations (classes) between Snellen (decimal, meter and feet), ETDRS, and logMAR. PDF Visual Acuity Score Conversion - Jaeb endobj ETDRS letter, in order to keep it as a measurement (not: NA). 2010. Novel Method for Analyzing Snellen Visual Acuity Measurements. Retina 30 (7). 2006. Visual Acuities Hand Motion and Counting Fingers Can Be Quantified with the Freiburg Visual Acuity Test. Investigative Ophthalmology & Visual Science 47 (3): 123640. eCollection 2023. 2009 Dec;107:311-24. Tiew S, Lim C, Sivagnanasithiyar T. Using an excel spreadsheet to convert Snellen visual acuity to LogMAR visual acuity. and JavaScript. o$eP.2F-F}G~fLhIHEoCZwByF9TIW&NM].aBM'?l!]Rh&Jlvg=` A-=x3=C;i{K!ggHIww#+ y"coI i Pl".a]:9!S"8`[0+e)]0TX jtv`wlox\6[Tp)A::"C|(C=g"qy#HUh.=_d#.J]{i\1/BRgiEiFef{zQZzKJ3bP>[#U} r@O8;[zt-)EP=lkC,y}rwvHc'KPRS qc+Hqm EX_+|IpE#l iYi6X"N{p0#!OPBV?#',pWE#>I>][BdMG?=Awr,3A.~Ji(Oi([it5x\S$(;aO=}QQ##Llq6C=> & Tiew, S. Using an excel spreadsheet to convert Snellen visual acuity to LogMAR visual acuityfurther explanation. Google Scholar. Although kind of nice, blink is more a nerdy extra and is not likely to be used much. if one of CF, HM, LP, PL, NLP, or NPL: Snellen fractions (meter/ feet) need to be entered as fraction with /. The score was further modified by adding/subtracting 0.02 logMAR to converted values for letters correctly/incorrectly identified on previous/next line. vector of va class. You can read the full text of this article if you: Keywords VA cleaning ePd*D _@!(N|u!0!gL0F6?%='=N]baTcdCA?$wdEBjFOV{cP0 |1?28SjVH*5)y91M3z-wfr?X}wIt.,U3[,{x|.27w"FX`K K W;I D{c2drIDn?jokscrMjc-"Xv5Z3&p{-w/UnS200ue0 `8=e&"1w+8CE~2y'f%k>-$Ge;TGO^5EJ}bEBn>b%;-+k7, 6#:(ku(\EJcbCpsQu+1zhYmTGXLv"iQ=(6-Vc+)&RZ(Vd|FuiQM+EJ}bEj![XVU+1uY[(Vu+1+!E7\E=T@P[iTn'4]eQP'\]O[+#WFOIu >JI5)9Ejz1_h*:N7bg0ke rxn Front Med (Lausanne). Snellen Notation (logMAR to Snellen conversion for 65 letters): 20/50. considered an exact science and any attempt to use formulas will result eye works smoother with tidy data, and with good names (any package does, really!). 2020;43:21489. Description they are unlikely to happen by chance as a wrong entry (and as integers), va: Visual acuity notation conversion in tjebo/eye: Analysis of Eye Data Snellen chart may be preferable over early treatment diabeti Eye 36, 1708 (2022). Data is temporarily unavailable. You can use recodeye for very convenient recoding. the VA chart are used. Thank you for visiting nature.com. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in 2001;85:4326. It will return a list object which gives you easy access to the data. Internet Explorer). Efficacy of small-incision lenticule extraction surgery in high astigmatism: A meta-analysis. Ophthalmic Physiol Opt. %PDF-1.5 Vector with visual acuity entries. 8600 Rockville Pike endobj 11 Confusion 2. Visual acuity testing. This is a simple function and should not require much explanation. ziXyS*(P9_"H3 PznjpPF"?9a{i\[$1&GPwa1W1"82zrX?7C=BH&LBOI"I`RAk}d Fazel F, Malekahmadi M, Feizi A, Oliya B, Tavakoli M, Fazel M. BMC Ophthalmol. endobj To Snellen: A linear relationship exists between true ETDRS letter scores, approxETDRS letter scores, and logMAR units. No. logMAR to ETDRS: logMAR rounded to the first digit and converted with the chart. 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. 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. a specific range (0-100). Snellen "+/-" entries A logMAR chart (Logarithm of the Minimum Angle of Resolution) is a chart consisting of rows of letters that is used by ophthalmologists, orthoptists, optometrists, and vision scientists to estimate visual acuity. The same outcomes (in Snellen fractions) were obtained with statistical manipulation of either approxETDRS letter scores or logMAR conversions. Any element which is implausible/ not recognized will be converted to NA. ?myop for help, #> From etdrs. 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. Cleans and converts visual acuity notations (classes) ISSN 1476-5454 (online) 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. The good (logMAR), the bad (Snellen) and the ugly (BCVA, number of Lim, C., De Silva, I. "etdrs", "logmar", "snellen" or "snellendec". official website and that any information you provide is encrypted Standardized ETDRS Testing - VectorVision 2023 M&S Technologies We measured their. 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. Any fractions allowed. 12 0 obj #> Specify eye column with "eye_col" argument, #> patid sex age avdays_induc ethnicity loaded time injgiven va regimen, #> , #> 1 id_1 m 60-69 28 se_asian TRUE 0 TRUE 0.30 ranibi, #> 2 id_1 m 60-69 28 se_asian TRUE 28 TRUE 0.30 ranibi, #> 3 id_1 m 60-69 28 se_asian TRUE 56 TRUE 0.30 ranibi, #> 4 id_1 m 60-69 28 se_asian TRUE 91 TRUE 0.40 ranibi, #> 5 id_1 m 60-69 28 se_asian TRUE 131 TRUE 0.46 ranibi, #> 6 id_1 m 60-69 28 se_asian TRUE 173 TRUE 0.40 ranibi, #> 7 id_1 m 60-69 28 se_asian TRUE 236 TRUE 0.50 ranibi, #> 8 id_1 m 60-69 28 se_asian TRUE 278 TRUE 0.50 ranibi, #> 9 id_1 m 60-69 28 se_asian TRUE 411 TRUE 0.60 ranibi, #> 10 id_1 m 60-69 28 se_asian TRUE 453 TRUE 0.54 ranibi, #> # with 118,245 more rows, and 1 more variable: pre2013 , #> [1] "name" "oculus" "eyepressure" "vision". #> maintained, but will be kept in the package. Again, good names and tidy data always help! Accessibility Kaiser [4] described how he prepared for statistical analysis by converting the Snellen fraction to logMAR. endobj 2010 Mar;30(2):200-3. doi: 10.1111/j.1475-1313.2009.00700.x. The Bailey-Lovie chart was also designed to be scored in logMAR units, making it easier to convert results based upon various viewing distances. All told, 413 patients (773 eyes) met the inclusion criteria for this study. R: Visual acuity notation conversion Must be atomic. Mean Snellen VA was 0.40 logMAR (20/50 Snellen equivalent), and mean ETDRS measurement was 0.27 logMAR (20/40 Snellen equivalent). in Snellen. a specific range (0-100). 2cgSgU - Google Groups 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. This calculator is intended as a convenient screener for visual acuity to be used on a mobile device and should not be used as a replacement for in-office testing.Evidence for smartphone apps for Snellen visual acuity is limited, and currently no app has been found to be accurate to within at least one line of formal visual acuity testing (and further validation is required). All told, 413 patients (773 eyes) met the inclusion criteria for this study. - https://doi.org/10.1167/iovs.05-0981 The user can specify the original VA notation, but va will check that and ignore the argument if implausible. As each row grew smaller, the amount of space between each row decreased. This, again, requires a certain format of names and codes - See Names and Codes. Search for Similar Articles Our data set consists of 100 patients who underwent corneal collagen cross linking. 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. Overall, 76.6% of eyes correctly identified more letters with the ETDRS chart. - https://doi.org/10.1167/iovs.05-0981 EDITORIAL The good (logMAR), the bad (Snellen) and the ugly (BCVA Smart System Reg U.S. Pat. <. eyes recognizes integer coding 0:1 and 1:2, with right being the lower number. In the meantime, to ensure continued support, we are displaying the site without styles plausibility_methods, 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. doi: 10.1097/iae.0b013e3181d87e04, ETDRS to logMAR: logMAR = -0.02 * etdrs + 1.7 M&S holds US Patent Numbers 7,354,155; 7,926,948; 8,167,429; 8,419,184; ), logMAR and ETDRS. The https:// ensures that you are connecting to the 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. For more information, please refer to our Privacy Policy. ## if you only want to rename one or a few columns: #> [1] "patID" "oculus" "eyepressure" "VA", ## information on the tested dimension is included ("iop"), ## VA and eye strings are separated by underscores, #> [1] "id" "surgery_right" "surgery_left" "iop_r_preop", #> [5] "iop_r_postop" "iop_l_preop" "iop_l_postop" "va_r_preop", #> [9] "va_r_postop" "va_l_preop" "va_l_postop", ## Id and Eye are common names, there are no spaces, ## VA is separated from the rest with an underscore, ## There is an unnecessary underscore (etdrs are always letters). Low vision is defined as a best-corrected visual acuity worse than 0.5 LogMAR but equal or better than 1.3 LogMAR in the better eye. Correspondence to endobj Snellen visual acuity measurements were converted to approximate ETDRS (approxETDRS) letter scores for statistical manipulations and then converted back to Snellen equivalent fractions. Wolters Kluwer Health integer coding 0:1 and 1:2, right eye being the lower number. Cleans and converts visual acuity notations (classes) [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.". Our data set consists of 100 patients who underwent corneal collagen cross linking. doi: 10.1016/s0002-9394(02)01825-1Beck et al., and Ferris FL, Kassoff A, Bresnick GH, Bailey I. hand movement and (no) perception of light, use logMAR ! Google Scholar. The cols argument takes a tidyselection. 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 . logMAR - Snellen Conversion Calculator ::: MyVisionTest.com Other VA converter: Factors Contributing to Discrepancy Between Visual Acuity Fractions Derived From a Snellen Chart and Letter Scores on the Early Treatment Diabetic Retinopathy Study Chart. VA Variability: Snellen Versus ETDRS Outcomes Internet Explorer). Suprachoroidal injection of triamcinolone acetonide plus intravitreal bevacizumab in diabetic macular edema: a randomized pilot trial. Understanding the ETDRS Chart and Scale in Eye Examinations - EyeCharts Beck et al. In the meantime, to ensure continued support, we are displaying the site without styles Other patents pending. any case allowed. Am J Ophthalmol. 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. Careers. An important step in eyes is the guessing of the columns that identify patients and eyes. numeric (for logMAR), or integer (for ETDRS). 2023 Jan 27;23(1):40. doi: 10.1186/s12886-023-02790-y. Michael Bach. and transmitted securely. 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]. It uses an S3 generic under the hood with methods for atomic vectors, data frames, and lists of either atomic vectors or data frames. . Kaiser PK. Beck, Roy W, Pamela S Moke, Andrew H Turpin, Frederick L Ferris, John Paul SanGiovanni, Chris A Johnson, Eileen E Birch, et al.2003. A Computerized Method of Visual Acuity Testing. American Journal of Ophthalmology 135 (2). The authors have no commercial or proprietary interest in any product or corporation mentioned in this article. ignoring plus/minus entries and just returning the From Snellen to ETDRS | M&S Technologies As with eyes(), myop() requires a specific data format. <>/PageLabels 249 0 R>> <> <> BCVA Trans Am Ophthalmol Soc. between Snellen (decimal, meter and feet), ETDRS, and logMAR. All Snellen and ETDRS VA measurements were converted to logMAR units for direct comparison, and the variability between measurements was calculated. see "Examples", ETDRS must be integer-equivalent between 0 and 100 (integer equivalent The site is secure. Snellen fractions need to be entered with "/". This is then bascially a wrapper around cleanVA. We converted all the Snellen visual acuities to logMAR visual acuities. Three out of 5 optotypes per line had to be correctly identified, while wrong answers were monitored. ## 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. Your message has been successfully sent to your colleague. ## But which dimension of "r"/"l" are we exactly looking at? For more information on customizing the embed code, read Embedding Snippets. If you are not happy with the automatic column selection, you can manually select the VA and IOP columns with the arguments va_cols or iop_cols. The mean BCVA in decimal notation was 0.970.15 and 0.970.18 with the Snellen and ETDRS charts, respectively (P =0.78). You can get creative with your snellens. In 1862, Snellen used a fractional notation in which the numerator indicated the actual viewing distance. For access, try logging in If you are subscribed to this group and have noticed abuse, report abusive group. Results: He was a colleague of Dr. Franciscus Donders. These conversions were done via our excel spreadsheet formula taking into account methods from our literature searches. https://doi.org/10.1097/iae.0b013e3181d87e04. which_va(). % Snellen-Logmar Calculator - Visual Impairment Network for Children