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 cylinder 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 cylinder
- 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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