Crate opticalc 

opticalc

Rust utilities for common clinical optics calculations used in optometry and ophthalmic settings.

Features

• Index conversion: Convert measured lens powers between assumed and actual refractive indices.
• Rx conversion: Scale full sphero‑cyl prescriptions between indices while preserving axis.
• Lensmeter simulation: Predict what a lensmeter would read for a true Rx at a different index.
• Induced prism: Compute horizontal/vertical prism from decentration using the full power matrix.
• Crossed cylinders and oblique meridian helpers.

Examples

use opticalc::*;

// Convert a measured power from 1.523 to 1.586
let true_power = convert_power(-4.463, 1.523, 1.586);

// Convert a full sphero‑cyl Rx between indices
let measured = SpheroCyl { sphere: -2.00, cylinder: -1.00, axis_deg: 180.0 };
let true_rx = convert_rx(measured, 1.523, 1.586);

// Simulate what a lensmeter @1.523 would read for a true Rx @1.586
let reading = simulate_lensmeter_reading(true_rx, 1.523, 1.586);

Induced prism from decentration (Prentice’s rule, full toric matrix):

use opticalc::*;

let lens = SpheroCyl { sphere: 2.0, cylinder: -1.0, axis_deg: 25.0 };
let dec = Decentration { horizontal_mm: 2.0, vertical_mm: -1.0 };
let p = induced_prism(Eye::OD, lens, dec);

// Access signed or magnitude/base components
let h_signed = p.horizontal.signed();
let v_signed = p.vertical.signed();
let mag = p.magnitude();

Structs

CombinedPrism

Represents combined horizontal and vertical prism components.

Decentration

Represents lens decentration relative to the optical center.

HorizontalPrism

Represents horizontal prism in prism diopters, with an explicit base direction.

SpheroCyl

Defines a sphero-cylinder lens.

VerticalPrism

Represents vertical prism in prism diopters, with an explicit base direction.

Enums

Eye

Defines the eye.

HorizontalBase

Base direction for horizontal prism relative to the patient.

VerticalBase

Base direction for vertical prism.

Constants

CROWN_GLASS_INDEX

Refractive index of Crown Glass (standard optical glass).

CR_39_INDEX

Refractive index of CR-39 (Columbia Resin #39).

HIGH_INDEX_160_INDEX

Refractive index of High-Index 1.60 plastic.

HIGH_INDEX_167_INDEX

Refractive index of High-Index 1.67 plastic.

HIGH_INDEX_174_INDEX

Refractive index of High-Index 1.74 plastic.

POLYCARBONATE_INDEX

Refractive index of Polycarbonate.

TRIVEX_INDEX

Refractive index of Trivex.

Functions

convert_power

Convert a lens power measured under an assumed refractive index to the true power for the actual material index.

convert_rx

Convert a full sph-cyl-axis Rx measured under an assumed index to the true Rx at the actual index. Axis is returned unchanged.

crossed_cylinders

Calculate Obliquely Crossed Cylinders

induced_prism

Compute induced prism using the full sphero-cylinder power matrix, including toric cross-terms, with OD/OS handling, returning clinical base directions.

minimum_blank_size

Calculate the minimum blank size for a single vision lens.

oblique_meridian

Oblique Meridian Power

recommended_blank_size

Calculate the recommended blank size including working edge border.

simulate_lensmeter_reading

Inverse of convert_rx: given the true Rx at the actual index, compute what a lensmeter calibrated to the assumed index would read. Axis is unchanged.

transpose

Transpose a spherocylindrical lens prescription to the opposite cylinder form.