This is a nomogram developed by Dr. John Dyer. This nomogram can be used to come up with the initial fitting parameters for size, optical zone, base curve, intermediate, and peripheral curves.
- Use the flattest curve as the primary curve in the first table
- Use the cyinder power of the Rx to find the base curve on the first table that corresponds to the correct primary curve and cylinder power
- Use the base curve to look in the second table for the corresponding parameters
- To calculate power take the Rx and transpose it to minus cyl
- Take the Rx and if over + or - 4.00D compensate the Rx for vertex distance
- For every 0.25D the base curve is over the primary curve add a 0.25D minus to the Rx
| Base Curve Determination (CPC) | ||||
|---|---|---|---|---|
| Primary Curve | 0.00 to 1.00DC | 1.25 to 2.00DC | 2.25 to 3.00DC | 3.25 to 4.00DC |
| 40.00 | 40.25 | 40.50 | 40.75 | 41.00 |
| 40.25 | 40.50 | 40.75 | 41.00 | 41.25 |
| 40.50 | 40.75 | 41.00 | 41.25 | 41.50 |
| 40.75 | 41.00 | 41.25 | 41.50 | 41.75 |
| 41.00 | 41.25 | 41.50 | 41.75 | 42.00 |
| 41.25 | 41.50 | 41.75 | 42.00 | 42.25 |
| 41.50 | 41.75 | 42.00 | 42.25 | 42.50 |
| 41.75 | 42.00 | 42.25 | 42.50 | 42.75 |
| 42.00 | 42.25 | 42.50 | 42.75 | 43.00 |
| 42.25 | 42.75 | 43.00 | 43.25 | 43.50 |
| 42.50 | 43.00 | 43.25 | 43.50 | 43.75 |
| 42.75 | 43.25 | 43.50 | 43.75 | 44.00 |
| 43.00 | 43.50 | 43.75 | 44.00 | 44.25 |
| 43.25 | 43.75 | 44.00 | 44.25 | 44.50 |
| 43.50 | 44.00 | 44.25 | 44.50 | 44.75 |
| 43.75 | 44.25 | 44.50 | 44.75 | 45.00 |
| 44.00 | 44.50 | 44.75 | 45.00 | 45.25 |
| 44.25 | 44.75 | 45.00 | 45.25 | 45.50 |
| 44.50 | 45.00 | 45.25 | 45.50 | 45.75 |
| 44.75 | 45.25 | 45.50 | 45.75 | 46.00 |
| 45.00 | 45.50 | 45.75 | 46.00 | 46.00 |
| 45.25 | 46.00 | 46.25 | 46.50 | 46.75 |
| 45.50 | 46.25 | 46.50 | 46.75 | 47.00 |
| 45.75 | 46.50 | 46.75 | 47.00 | 47.25 |
| 46.00 | 46.75 | 47.00 | 47.25 | 47.50 |
| 46.25 | 47.00 | 47.25 | 47.50 | 47.75 |
| 46.50 | 47.25 | 47.50 | 47.75 | 48.00 |
| 46.75 | 47.50 | 47.75 | 48.00 | 48.25 |
| 47.00 | 47.75 | 48.00 | 48.25 | 48.50 |
| 47.25 | 48.00 | 48.25 | 48.50 | 48.75 |
| 47.50 | 48.25 | 48.50 | 48.75 | 49.00 |
| 47.75 | 48.50 | 48.75 | 49.00 | 49.25 |
| 48.00 | 48.75 | 49.00 | 49.25 | 49.50 |
| Lens Parameters | ||||
|---|---|---|---|---|
| Base Curve (CPC) | Diameter (mm) | Optical Zone (mm) | Intermediate Peripheral Curve (mm/D) | Posterior Peripheral Curve (mm/D) |
| 40.00 | 9.0 | 7.6 | 0.2/36.00 0.2/32.00 | 0.3/27.50 |
| 40.50 | 8.9 | 7.5 | 0.2/36.00 0.2/32.00 | 0.3/27.50 |
| 41.00 | 8.8 | 7.4 | 0.2/37.00 0.2/33.00 | 0.3/27.50 |
| 41.50 | 8.7 | 7.3 | 0.2/37.00 0.2/33.00 | 0.3/27.50 |
| 42.00 | 8.6 | 7.2 | 0.2/38.00 0.2/34.00 | 0.3/27.50 |
| 42.50 | 8.5 | 7.1 | 0.2/38.00 0.2/34.00 | 0.3/27.50 |
| 43.00 | 8.4 | 7.0 | 0.239.00 0.2/35.00 | 0.3/29.00 |
| 43.50 | 8.3 | 6.9 | 0.2/39.00 0.2/35.00 | 0.3/29.00 |
| 44.00 | 8.2 | 6.8 | 0.2/40.00 0.2/36.00 | 0.3/29.00 |
| 44.50 | 8.1 | 6.7 | 0.2/40.00 0.2/36.00 | 0.3/29.00 |
| 45.00 | 8.0 | 6.6 | 0.2/41.00 0.2/37.00 | 0.3/31.00 |
| 45.50 | 7.9 | 6.5 | 0.2/41.00 0.2/37.00 | 0.3/31.00 |
| 46.00 | 7.8 | 6.4 | 0.2/42.00 0.2/38.00 | 0.3/31.00 |
| 46.50 | 7.7 | 6.3 | 0.2/42.00 0.2/38.00 | 0.3/31.00 |
| 47.00 | 7.6 | 6.2 | 0.2/43.00 0.2/39.00 | 0.3/33.00 |
| 47.50 | 7.5 | 6.1 | 0.2/43.00 0.2/39.00 | 0.3/33.00 |
| 48.00 | 7.4 | 6.0 | 0.2/44.00 0.2/40.00 | 0.3/33.00 |
| 48.50 | 7.3 | 5.9 | 0.2/44.00 0.2/40.00 | 0.3/33.00 |
| 49.00 | 7.2 | 5.8 | 0.2/45.00 0.2/41.00 | 0.3/35.00 |
| 49.50 | 7.1 | 5.7 | 0.2/45.00 0.2/41.00 | 0.3/35.00 |
| 50.00 | 7.0 | 5.6 | 0.2/46.00 0.2/42.00 | 0.3/35.00 |
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