Table 2.

Categories of Electronic Health Record VA Entries for Data Analysis

Category		Description	Examples	Interpretation Outcome
Usable	1. Exact match	Conformance to the data dictionary∗	20/20, 20/32, 20/500, CF	Use as is
	2. Conditional conformance	Entry references VA lines partially read, reflecting the inclusion of letter count with or without subsequent alpha-descriptors; can be conformed to the data dictionary∗	20/50−2+3 → 20/50 20/100−1 moving head around → 20/100	For categories 2 and 3: • Extract numeric VA measures or standard observations only • Disregard counting letter or narrative information • Conform VA line measures and observations to allowed values defined by the data dictionary∗
	3. Convertible conformance	Entry can be conformed to the data dictionary∗ after conversion, - Includes alpha-descriptors or modifiers - Recorded at test distances inconsistent with the data dictionary - Reflects typographical documentation errors, variations in language descriptors or observations	20/20 blurry → 20/20 NI 20/50 → 20/50 5/200 letters missing → 20/800 CF@3ft → CF Tumbling E@2M → 20/400 20/12 → 20/12.5 prosthetic → NLP posthetic → NLP
	4. Plausible, not conformed	Entry did not conform to the data dictionary∗ but could be plausible	5/400 1/125	May use depending on research question, the data dictionary, and internal documentation idiosyncrasies
Not usable		Number strings, nonsensical fractions, and misplaced data	20825, 2525, 60/64, 070, 20/0, 820/25, 0.35, +3.50, 1920/20	Recorded data not plausible and deemed as missing data
		Single number recorded	15, 18, 20, 35, 40, 070, 200
		Interpretation deemed arbitrary	VA recorded as 20/020, possible VA interpretations include 20/20, 20/200, 2/200 (“200-size letter E”)

CF = counting fingers; NI = no improvement; NLP = no light perception; VA = visual acuity.

^∗Data dictionary: internal standard listing of VA line measurements and observations that meet conformance and plausibility standards (Fig 1).