Prescription

Bases: BaseModel

The prescription module contains methods to deal with spectacle prescriptions.

Examples:

Typical use:

>>> rx = Prescription(sphere=0, cylinder=-1, axis=180)
>>> str(rx)
'plano / -1.00 x 180'
>>> rx = Prescription(sphere=1, add={"add": 1})
>>> str(rx)
'+1.00 DS Add: +1.00 @ 40cm'

mean_sphere() property

Provide mean sphere value of the prescription.

Returns:

Type	Description
float	The Mean Sphere.

transpose(flag=None)

Transpose prescription from positive to negative and vice versa.

Flags, 'n' and 'p', can be provided to force a negative or positive cylinder respectively.

Parameters:

Name	Type	Description	Default
(Optional[[Literal["n",	"p"]]	Flag to force negative ('n') and positive ('p') cylindrical format. Defaults to None.	required

Examples:

Transposing a prescription as normal:

>>> rx = Prescription("+1.00/-1.00x180")
>>> rx.transpose()
>>> str(rx)
"plano / +1.00 x 90"
>>> rx.transpose()
>>> str(rx)
"+1.00 / -1.00 x 180"

Transposing a prescription with the 'n' flag:

>>> rx = Prescription("+1.00/-1.00x180").transpose('n')
>>> str(rx)
"+1.00 / -1.00 x 180"

parse(rx)

Parse a prescription in a more typical format.

This is more familiar than setting a prescription using keyword arguments.

Parameters:

Name	Type	Description	Default
rx	str	The prescription as a string.	required

Examples:

Parsing a simple prescription:

>>> rx = Prescription().parse("+1.00/-1.00x180")
>>> rx.transpose()
>>> str(rx)
'pl / +1.00 x 90'

random(rx_range=30, seed=None)

Generate a random prescription.

All results will produce negative cylinderical results. Use the transpose() method to return positive cylindrical results.

Parameters:

Name	Type	Description	Default
rx_range	float	The +/- range of prescription in dioptres.	30
seed	Optional[int]	Seed for setting random.seed().	None

Examples:

Typical use:

>>> rx = Prescription().random()
>>> str(rx)
'+1.00 / -1.00 x 173'