.optical-calculator-container {
background-color: #f9f9f9;
border: 1px solid #ccc;
border-radius: 8px;
padding: 20px;
max-width: 700px;
margin: 20px auto;
font-family: Arial, sans-serif;
box-shadow: 0 4px 8px rgba(0,0,0,0.1);
}
.optical-calculator-container h1, .optical-calculator-container h2, .optical-calculator-container h3 {
color: #333;
text-align: center;
}
.optical-calculator-form {
display: grid;
grid-template-columns: 1fr;
gap: 15px;
margin-bottom: 20px;
}
@media (min-width: 600px) {
.optical-calculator-form {
grid-template-columns: repeat(3, 1fr);
}
}
.optical-calculator-form .input-group {
display: flex;
flex-direction: column;
}
.optical-calculator-form label {
font-weight: bold;
margin-bottom: 5px;
color: #555;
}
.optical-calculator-form input[type="number"] {
padding: 10px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
-moz-appearance: textfield;
}
.optical-calculator-form input[type="number"]::-webkit-outer-spin-button,
.optical-calculator-form input[type="number"]::-webkit-inner-spin-button {
-webkit-appearance: none;
margin: 0;
}
.optical-calculator-button {
background-color: #0073aa;
color: white;
border: none;
padding: 12px 20px;
font-size: 18px;
border-radius: 5px;
cursor: pointer;
width: 100%;
margin-top: 10px;
grid-column: 1 / -1;
}
.optical-calculator-button:hover {
background-color: #005a87;
}
#optical-result-container {
background-color: #e9f5ff;
border: 1px solid #b3d7f2;
border-radius: 5px;
padding: 15px;
margin-top: 20px;
text-align: center;
}
#optical-result-container h3 {
margin-top: 0;
color: #005a87;
}
#optical-result-container p {
font-size: 1.2em;
margin: 10px 0;
color: #333;
}
#optical-result-container .error-message {
color: #d9534f;
font-weight: bold;
}
.optical-content {
margin-top: 30px;
line-height: 1.6;
}
.optical-content h2 {
text-align: left;
border-bottom: 2px solid #0073aa;
padding-bottom: 5px;
margin-top: 30px;
}
.optical-content p, .optical-content ul {
text-align: left;
}
.optical-content .disclaimer {
background-color: #fffbe6;
border: 1px solid #ffe58f;
padding: 15px;
border-radius: 4px;
font-size: 0.9em;
color: #8a6d3b;
}
Minus Cylinder to Plus Cylinder Converter
Easily convert your eyeglass prescription from minus cylinder (-) notation to plus cylinder (+) notation with this simple tool.
Converted Plus Cylinder Prescription
Understanding Your Eyeglass Prescription
An eyeglass prescription has three main components for correcting vision:
- Sphere (SPH): This indicates the lens power, measured in diopters, to correct nearsightedness (myopia) or farsightedness (hyperopia). A minus sign (-) indicates correction for nearsightedness, while a plus sign (+) indicates correction for farsightedness.
- Cylinder (CYL): This indicates the lens power for astigmatism. It represents the difference in power between the two main meridians of the eye. It can be written with a minus or plus sign.
- Axis: This is a number between 1 and 180 that indicates the orientation of the astigmatism. It's the meridian of the lens that contains no cylinder power.
Minus vs. Plus Cylinder Notation
Minus cylinder and plus cylinder are two different conventions for writing the exact same prescription. Neither is better than the other, but different professionals may prefer one format. Optometrists commonly use the minus cylinder format, while ophthalmologists and lens manufacturing labs sometimes use the plus cylinder format. This calculator helps you translate between them.
How to Manually Convert from Minus to Plus Cylinder
The conversion, also known as transposition, follows three simple rules:
- Calculate the New Sphere: Add the original sphere and cylinder values together.
- Calculate the New Cylinder: Change the sign of the original cylinder value. For example, -1.50 becomes +1.50.
- Calculate the New Axis: If the original axis is 90 or less, add 90. If the original axis is greater than 90, subtract 90.
Example Conversion
Let's convert a sample minus cylinder prescription:
Original Prescription: SPH -2.50 / CYL -1.00 / Axis 170
- New Sphere: (-2.50) + (-1.00) = -3.50
- New Cylinder: -(-1.00) = +1.00
- New Axis: 170 is greater than 90, so 170 – 90 = 80
Converted Plus Cylinder Prescription: SPH -3.50 / CYL +1.00 / Axis 80
Disclaimer: This calculator is for informational purposes only and should not be used to replace a prescription from a qualified eye care professional. Always consult your optometrist or ophthalmologist for any questions regarding your eye health and prescription. An incorrect prescription can cause eye strain, headaches, and blurry vision.
function formatPower(value) {
if (value > 0) {
return '+' + value.toFixed(2);
}
return value.toFixed(2);
}
function calculatePlusCylinder() {
var sphereInput = document.getElementById('sphere').value;
var cylinderInput = document.getElementById('cylinder').value;
var axisInput = document.getElementById('axis').value;
var sphere = parseFloat(sphereInput);
var cylinder = parseFloat(cylinderInput);
var axis = parseInt(axisInput);
var resultDiv = document.getElementById('result');
var resultContainer = document.getElementById('optical-result-container');
resultContainer.style.display = 'block';
if (isNaN(sphere) || isNaN(cylinder) || isNaN(axis)) {
resultDiv.innerHTML = 'Please enter valid numbers in all fields.';
return;
}
if (cylinder > 0) {
resultDiv.innerHTML = 'This calculator converts from MINUS cylinder. Please enter a negative value for the cylinder.';
return;
}
if (cylinder === 0) {
resultDiv.innerHTML = 'No cylinder value was entered, so no conversion is necessary.' +
'
Sphere: ' + formatPower(sphere) + " +
'
Cylinder: 0.00′ +
'
Axis: N/A';
return;
}
if (axis 180) {
resultDiv.innerHTML = 'The Axis value must be between 1 and 180.';
return;
}
// 1. Calculate New Sphere
var newSphere = sphere + cylinder;
// 2. Calculate New Cylinder
var newCylinder = -cylinder;
// 3. Calculate New Axis
var newAxis;
if (axis <= 90) {
newAxis = axis + 90;
} else {
newAxis = axis – 90;
}
resultDiv.innerHTML = '
Sphere: ' + formatPower(newSphere) + " +
'
Cylinder: ' + formatPower(newCylinder) + " +
'
Axis: ' + newAxis + ";
}