visual_acuity_converter: Visual Acuity Testing Converter (Snellen)

In cliot: Clinical Indices and Outcomes Tools

Visual Acuity Testing Converter (Snellen)

Description

Converts standard Snellen visual acuity (measured at 20 feet) into other common clinical notations, including Metric (6 meters), Decimal, and LogMAR. This utility assists in standardizing visual acuity records across different medical systems and research protocols.

Usage

visual_acuity_converter(snellen_denominator)

Arguments

snellen_denominator

Numeric. The denominator of the visual acuity fraction when the numerator is 20 (e.g., entered as 20 for 20/20 vision, 40 for 20/40 vision). Must be a positive number.

Details

The conversions are based on the following relationships:

• Decimal = 20 / Snellen Denominator

• Metric Denominator = Snellen Denominator * 0.3

• LogMAR = -log10(Decimal Acuity)

Value

A list containing the converted values:

Snellen_Imperial	The standard US notation (e.g., "20/20").
Snellen_Metric	The metric notation used in many other countries (e.g., "6/6").
Decimal	The decimal equivalent (e.g., 1.0 for 20/20, 0.5 for 20/40).
LogMAR	The Logarithm of the Minimum Angle of Resolution.

References

Holladay JT. Visual acuity measurements. J Cataract Refract Surg. 2004;30(2):287-290. doi:10.1016/j.jcrs.2004.01.014

Examples

# Example 1: 20/40 vision
visual_acuity_converter(40)

# Example 2: 20/200 vision (Legal Blindness boundary in US)
visual_acuity_converter(200)

cliot documentation built on Dec. 1, 2025, 1:06 a.m.