ETDRS –> LogMAR conversion

Convert ETDRS score to LogMAR units

Usage

convert_etdrs_to_logmar(value)

Arguments

value

object containing ETDRS score to convert to logMAR.

Permitted values

a numeric value, e.g. 2, -5, 1.4

Default value

none

Value

The input value converted converted to logMAR units.

Details

ETDRS value converted to logMAR as:

$$logMAR = -0.02 * ETDRS + 1.7$$

Source for conversion formula: Beck, R.W., et al. A computerized method of visual acuity testing. American Journal of Ophthalmology, 135(2), pp.194-205. doi:https://doi.org/10.1016/s0002-9394(02)01825-1.

See also

convert_logmar_to_etdrs()

Author

Rachel Linacre

Examples

library(tibble)
library(dplyr)
#> 
#> Attaching package: ‘dplyr’
#> The following objects are masked from ‘package:stats’:
#> 
#>     filter, lag
#> The following objects are masked from ‘package:base’:
#> 
#>     intersect, setdiff, setequal, union
library(admiral)

oe <- tribble(
  ~STUDYID, ~USUBJID, ~OETESTCD, ~OEMETHOD, ~OESTRESN,
  "XXX001", "P01", "VACSCORE", "logMAR EYE CHART", 1.08,
  "XXX001", "P02", "VACSCORE", "logMAR EYE CHART", 1.66,
  "XXX001", "P03", "VACSCORE", "logMAR EYE CHART", 1.60,
  "XXX001", "P04", "VACSCORE", "ETDRS EYE CHART", 57,
  "XXX001", "P05", "VACSCORE", "ETDRS EYE CHART", 62
)

adbcva <- oe %>%
  filter(OETESTCD == "VACSCORE" & toupper(OEMETHOD) == "ETDRS EYE CHART") %>%
  mutate(AVAL_LOGMAR = convert_etdrs_to_logmar(OESTRESN))

adbcva
#> # A tibble: 2 × 6
#>   STUDYID USUBJID OETESTCD OEMETHOD        OESTRESN AVAL_LOGMAR
#>   <chr>   <chr>   <chr>    <chr>              <dbl>       <dbl>
#> 1 XXX001  P04     VACSCORE ETDRS EYE CHART       57        0.56
#> 2 XXX001  P05     VACSCORE ETDRS EYE CHART       62        0.46