| Utility |
Traditional bi, tri,
and quad curve GP lens designs
Lathe cut to roder from the material of your choice.
Front Toric, Back Toric, and Bi-Toric Available. |
| Base Curves |
Any |
| Sphere Powers |
-30.00 D. to +30.00
D. in 0.125 D. steps |
| Cylinder Powers |
-0.500 D. to -10.00
D. in 0.125 D. steps |
| Diameters |
Any |
| Optical Zones |
Any, 1.40 mm smaller
than diameter as standard |
| 2nd Radius |
Any, 1.20 mm flatter
than base curve as standard |
| Edge Bevels |
Any, 0.20 mm width
/ 11.00 mm radius as standard |
| Manufacture |
Fully lathe cut to
order on CNC lathes |
| Materials |
Any |
| Downloads |
• Product
White Sheet (PDF) |
| Diagnostic Fitting
Procedure |
| Base Curve / Diameter |
• Select an appropriate
diagnostic lens based on K readings and corneal
diameter size.
• Using standard fitting techniques and criteria,
observe the diagnostic lens for position, movement
and fluoroscein pattern. Refine the fit as needed. |
| BV Power |
Obtain an over-refraction
over the best fitting diagnostic lens. Combine
the spherical value of the over-refraction with
the Diagnostic lens power to determine the final
contact lens power required.
Note: Specifying Intermediate and Peripheral
curves
Alden Optical Laboratories will apply our standard
intermediate and peripheral curves if not specified
by the practitioner. Intermediate (secondary)
curves are typically 1.2mm flatter than the base
curve. Peripheral curves are generally 2.0 to
3.0mm flatter than intermediate curve and .2 to
.3 wide. |
| Empirical
Fitting Procedure |
| Base
Curve |
Amount
of Corneal Cylinder |
Base
Curve Selection |
| 0.00
to 1.00 D. |
Fit on flat K to
0.25D. steeper than flat K |
| 1.25
to 2.00 D. |
Fit 0.25D. to 0.50D.
steeper than flat K |
| 2.25
to 3.00 D. |
Fit 0.50D. to 0.75D.
steeper than flat K |
| Diameter
/ Optical Zone |
Base
Curve |
Diameter
(suggested) |
Optical
Zone (suggested) |
| 6.99 & steeper |
8.80 |
7.20 |
| 7.00 to 7.39 |
8.80 |
7.40 |
| 7.40 to 7.79 |
9.00 |
7.40 |
| 7.80 to 8.19 |
9.20 |
7.60 |
| 8.20 & Flatter |
9.40 |
7.80 |
| Power |
• Convert spectacle
Rx to minus cylinder form.
• Adjust power for vertex distance if greater
than 4.00 D. Determine tear lens power by calculating
the difference between base curve and flat K.
Combine the spherical component of the spectacle
Rx (corrected for vertex distance when required)
with the tear lens power to obtain the final contact
lens power required.
• Or, provide our consultation department
with K readings and spectacle Rx, and let us design
your lenses for you. |
