opticalc

JavaScript/TypeScript utilities for common clinical optics calculations used in optometry and ophthalmic settings.

Installation

npm install opticalc

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

Usage

Basic Power Conversion

import { convertPower } from 'opticalc';

// Convert a measured power from 1.523 to 1.586
const truePower = convertPower(-4.463, 1.523, 1.586);
console.log(truePower); // -4.25

TypeScript

import { convertPower, SpheroCyl, convertRx, simulateLensmeterReading } from 'opticalc';

// Convert a full sphero‑cyl Rx between indices
const measured: SpheroCyl = { 
  sphere: -2.00, 
  cylinder: -1.00, 
  axisDeg: 180.0 
};

const trueRx = convertRx(measured, 1.523, 1.586);
console.log(trueRx);

// Simulate what a lensmeter @1.523 would read for a true Rx @1.586
const reading = simulateLensmeterReading(trueRx, 1.523, 1.586);
console.log(reading);

Induced Prism from Decentration

import { inducedPrism, Eye } from 'opticalc';

const lens = { sphere: 2.0, cylinder: -1.0, axisDeg: 25.0 };
const decentration = { horizontalMm: 2.0, verticalMm: -1.0 };
const prism = inducedPrism(Eye.OD, lens, decentration);

// Access signed or magnitude/base components
const hSigned = prism.horizontal.signed();
const vSigned = prism.vertical.signed();
const magnitude = prism.magnitude();

Common.js

const { convertPower, convertRx } = require('opticalc');

const power = convertPower(-4.463, 1.523, 1.586);
console.log(power);

API Reference

Functions

• convertPower(measuredPower, fromIndex, toIndex) - Convert lens power between refractive indices
• convertRx(spheroCyl, fromIndex, toIndex) - Convert full prescription between indices
• simulateLensmeterReading(trueRx, lensmeterIndex, trueIndex) - Simulate lensmeter reading
• inducedPrism(eye, lens, decentration) - Calculate induced prism from decentration

Types

• SpheroCyl - Sphero-cylindrical prescription
• Decentration - Horizontal and vertical decentration in mm
• Eye - Enum for OD (right) and OS (left) eyes
• Prism - Prism power with horizontal/vertical components

Browser Support

This package uses WebAssembly and requires a modern browser with WebAssembly support:

• Chrome 57+
• Firefox 52+
• Safari 11+
• Edge 16+

License

MIT