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Value of Two Prisms Stacked in the Same Direction

Calculator

<html> <head> 

  <title>Stacked Prism Value Lookup</title>
  <style>
      #header {
          display: none;
      }
      body {
          font-family: Arial, sans-serif;
          margin: 20px;
          padding: 20px;
      }
      h2 {
          color: #333;
      }
      label {
          font-weight: bold;
      }
      input, button {
          margin-top: 5px;
          padding: 8px;
          font-size: 16px;
      }
      p {
          font-size: 18px;
          font-weight: bold;
          color: blue;
          margin-top: 10px;
      }
  </style>
  <script>
      const prismTable = {
          10: {1: 11, 2: 12, 3: 13, 4: 14, 5: 15, 6: 16, 7: 17, 8: 19, 9: 20, 10: 21, 12: 23, 14: 25, 16: 28, 18: 30, 20: 33, 25: 39, 30: 46, 35: 53, 40: 60, 45: 68, 50: 77},
          12: {1: 13, 2: 14, 3: 15, 4: 16, 5: 17, 6: 19, 7: 20, 8: 21, 9: 22, 10: 23, 12: 25, 14: 28, 16: 30, 18: 33, 20: 35, 25: 42, 30: 49, 35: 57, 40: 65, 45: 74, 50: 84}, 
          14: {1: 15, 2: 16, 3: 17, 4: 18, 5: 20, 6: 21, 7: 22, 8: 23, 9: 24, 10: 25, 12: 28, 14: 30, 16: 33, 18: 35, 20: 38, 25: 45, 30: 53, 35: 61, 40: 70, 45: 80, 50: 91}, 
          16: {1: 17, 2: 18, 3: 19, 4: 21, 5: 22, 6: 23, 7: 24, 8: 25, 9: 27, 10: 28, 12: 30, 14: 33, 16: 36, 18: 38, 20: 41, 25: 49, 30: 57, 35: 66, 40: 76, 45: 87, 50: 100}, 
          18: {1: 19, 2: 20, 3: 22, 4: 23, 5: 24, 6: 25, 7: 26, 8: 28, 9: 29, 10: 30, 12: 33, 14: 35, 16: 38, 18: 41, 20: 44, 25: 52, 30: 61, 35: 71, 40: 82, 45: 95, 50: 110},
          20: {1: 21, 2: 23, 3: 24, 4: 25, 5: 26, 6: 27, 7: 29, 8: 30, 9: 31, 10: 33, 12: 35, 14: 38, 16: 41, 18: 44, 20: 47, 25: 56, 30: 66, 35: 76, 40: 89, 45: 104, 50: 122},
          25: {1: 27, 2: 28, 3: 29, 4: 30, 5: 32, 6: 33, 7: 35, 8: 36, 9: 37, 10: 39, 12: 42, 14: 45, 16: 49, 18: 52, 20: 56, 25: 66, 30: 78, 35: 93, 40: 110, 45: 133, 50: 165},
          30: {1: 32, 2: 33, 3: 35, 4: 36, 5: 38, 6: 39, 7: 41, 8: 42, 9: 44, 10: 46, 12: 49, 14: 53, 16: 57, 18: 61, 20: 66, 25: 78, 30: 94, 35: 114, 40: 141, 45: 183, 50: 265},
          35: {1: 37, 2: 39, 3: 40, 4: 42, 5: 44, 6: 45, 7: 47, 8: 49, 9: 51, 10: 53, 12: 57, 14: 61, 16: 66, 18: 71, 20: 76, 25: 93, 30: 114, 35: 144, 40: 195, 45: 315},
          40: {1: 43, 2: 45, 3: 46, 4: 48, 5: 50, 6: 52, 7: 54, 8: 56, 9: 58, 10: 60, 12: 65, 14: 70, 16: 76, 18: 82, 20: 89, 25: 110, 30: 141, 35: 195, 40: 339},
          45: {1: 48, 2: 50, 3: 52, 4: 54, 5: 56, 6: 59, 7: 61, 8: 63, 9: 66, 10: 68, 12: 74, 14: 80, 16: 87, 18: 95, 20: 104, 25: 133, 30: 183, 35: 315},
          50: {1: 54, 2: 56, 3: 58, 4: 61, 5: 63, 6: 66, 7: 68, 8: 71, 9: 74, 10: 77, 12: 84, 14: 91, 16: 100, 18: 110, 20: 122, 25: 165, 30: 265}
      };
      function lookupValue() {
          let prism1 = document.querySelector('input[name="prism1"]:checked').value;
          let prism2 = document.querySelector('input[name="prism2"]:checked').value;
          
          prism1 = parseInt(prism1);
          prism2 = parseInt(prism2);
          
          if (prismTable[prism2] && prismTable[prism2][prism1] !== undefined) {
              document.getElementById("result").innerHTML = `Result: <strong>${prismTable[prism2][prism1]} Prism Diopters</strong>`;
          } else {
              document.getElementById("result").innerText = "Invalid input";
          }
      }
  </script>

</head> <body> 

  <h2 id="header">Prism Value of Two Prisms Stacked in the Same Direction</h2>
  <label>Select Initial Prism (PD):</label>
  <br>
  <input type="radio" name="prism2" value="10"> 10
  <input type="radio" name="prism2" value="12"> 12
  <input type="radio" name="prism2" value="14"> 14
  <input type="radio" name="prism2" value="16"> 16
  <input type="radio" name="prism2" value="18"> 18
  <input type="radio" name="prism2" value="20"> 20
  <input type="radio" name="prism2" value="25"> 25
  <input type="radio" name="prism2" value="30"> 30
  <input type="radio" name="prism2" value="35"> 35
  <input type="radio" name="prism2" value="40"> 40
  <input type="radio" name="prism2" value="45"> 45
  <input type="radio" name="prism2" value="50"> 50
  <br><br>
  <label for="prism1">Select Prism Stacked On Top (PD): </label>
  <br>
  <input type="radio" name="prism1" value="1"> 1
  <input type="radio" name="prism1" value="2"> 2
  <input type="radio" name="prism1" value="3"> 3
  <input type="radio" name="prism1" value="4"> 4
  <input type="radio" name="prism1" value="5"> 5
  <input type="radio" name="prism1" value="6"> 6
  <input type="radio" name="prism1" value="7"> 7
  <input type="radio" name="prism1" value="8"> 8
  <input type="radio" name="prism1" value="9"> 9
  <input type="radio" name="prism1" value="10"> 10
  <input type="radio" name="prism1" value="12"> 12
  <input type="radio" name="prism1" value="14"> 14
  <input type="radio" name="prism1" value="16"> 16
  <input type="radio" name="prism1" value="18"> 18
  <input type="radio" name="prism1" value="20"> 20
  <input type="radio" name="prism1" value="25"> 25
  <input type="radio" name="prism1" value="30"> 30
  <input type="radio" name="prism1" value="35"> 35
  <input type="radio" name="prism1" value="40"> 40
  <input type="radio" name="prism1" value="45"> 45
  <input type="radio" name="prism1" value="50"> 50
  <br><br>
  <button onclick="lookupValue()">Lookup</button>
  <br>
  <br>
  <p id="result"></p>

</body> </html>

<button type=“primary” size=“sm”>Reset Calculator</button>

Table

1st Prism
2nd Prism 10Δ 20Δ 30Δ 40Δ 50Δ
10Δ 21 33 46 60 77
20Δ 33 47 66 89 122
30Δ 46 66 94 141 264
40Δ 60 89 141 339
50Δ 77 122 256

Adapted From: Thompson & Guyton. Ophthalmic Prisms: Measurement Errors and How to Minimize Them. Ophthalmology 1983;90:204-2010

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