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LogMAR –> ETDRS conversion

Source: R/convert_logmar_to_etdrs.R
convert_logmar_to_etdrs.Rd

Convert LogMAR score to ETDRS units

Usage

convert_logmar_to_etdrs(value)

Arguments

value

object containing logMAR score to convert to ETDRS.

Permitted values

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

Default value

none

Value

The input value converted to ETDRS units.

Details

logMAR value converted to ETDRS as:

$$ETDRS = -(logMAR - 1.7) / 0.02$$

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.

Author

Nandini R Thampi

Examples

library(tibble)
library(dplyr)
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", 1
)

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