Visual Acuity

Bases: BaseModel

The visual_acuity module contains methods in handling visual acuity measurements.

Input for this class can be provided as keyword arguments. However, a string such as '6/6' can be parsed as well.

Parameters:

Name	Type	Description	Default
numerator	int	The test distance.	required
denominator	int	This distance required to subtend 5 minutes of arc.	required
unit	Literal[ft, m]	Takes feet or metres/meters only. Defaults to 'm', but please check examples for nuances.	required

Examples:

Typical use:

>>> va = VisualAcuity(numerator=6, denominator=6)
>>> str(va)
'6/6'

If you want to explicitly mention the units:

>>> va_feet = VisualAcuity(numerator=20, numerator=20, unit="ft")
>>> str(va_feet)
'20/20'

Parsing more familiar input:

>>> va_familiar = VisualAcuity('6/120')
>>> va_familiar
VisualAcuity(numerator=6.0, denominator=120.0, unit='m')

If the numerator is greater 6, then the unit is assumed to be feet.

>>> va_familiar_ft = VisualAcuity('20/200')
>>> va_familiar_ft
VisualAcuity(numerator=20.0, denominator=200.0, unit='ft')

m() property

Return snellen fraction in metres/meters.

Returns:

Name	Type	Description
str	str	Snellen Fraction in meters/metres.

Examples:

Typical use:

>>> va = VisualAcuity('20/20')
>>> va.m
'6/6'

ft() property

Return snellen fraction representation in feet.

Returns:

Type	Description
str	Snellen Fraction in feet.

Examples:

Typical use:

>>> va = VisualAcuity('6/6')
>>> va.ft
'20/20'

snellen_fraction() property

Return snellen fraction representation of visual acuity.

Returns:

Name	Type	Description
str	str	snellen fraction.

Examples:

Typical use:

>>> VisualAcuity("6 / 12").snellen_fraction
"6/6"

parse(va)

Parse a string into a visual acuity.

Note: if the test distance (numerator) is greater than 6, then the unit is assumed to be in feet.

Parameters:

Name	Type	Description	Default
va	str	A visual acuity.	required

Examples:

Parsing a visual acuity:

>>> va = VisualAcuity().parse('6/120')
>>> str(va)
'6/120'
Parsing a visual acuity, automatically turning into a feet:
>>> va = VisualAcuity().parse('20/20')
>>> va.unit
'ft'

decimal() property

Return decimal form of visual acuity.

Returns:

Name	Type	Description
Decimal	Decimal	Decimal form of visual acuity.

Examples:

Typical use:

>>> VisualAcuity("6/12").decimal
0.5

logmar() property

Return logmar value of the visual acuity.

Returns:

Name	Type	Description
Decimal	Decimal	Logmar value of the visual acuity.

Examples:

Typical use:

>>> VisualAcuity("6/6").logmar
0.0