- Technical Drawings
|Water Content (%)||72|
|Dk (35°C, Fatt Units)||42|
|Refractive Index Dry||1.513|
|Refractive Index Hydrated (35°C)||1.384|
|Linear Expansion (mm)||1.560|
|Radial Expansion (mm)||1.560|
|Hardness (Shore D)||84|
|% Transmission (@500 nm)||>95|
|Standard size||Diameter - 12.70 mm, Thickness - 5.0mm|
|Standard Colors||Clear, Blue|
|UV Blocker||Available upon request|
|Precut||Available upon request|
|Note||Optional sizing and colors may be available on request.|
|We recommend maintaining a maximum Relative Humidity range of 30 to 40% at 21 ± 2°C|
|Base Curve||Speed (RPM)||Feed (mm/min)||Depth (mm)|
|Front Curve||Speed (RPM)||Feed (mm/min)||Depth (mm)|
Machining parameters and tool specifications are important for optimum surface finish and reaching precise target every time. Benz R&D validates the expansion values, target hitting ability and surface quality of every lot of Benz materials when machined strictly according to recommendations.
G72-HW should need minimal polishing or no polishing because of the expansion of this material upon hydration. If polishing is required, use XPAL, Alox 721 or comparable material. Polishing time should be a maximum of 20 seconds.
A two-step process best achieves lens hydration for this type of ionic material. Step 1: hydrate lenses for a minimum of 14 hours at a constant temperature of 20 ± 2°C, while stirring, in a pH 8.2 isotonic saline solution. Step 2: transfer the lenses into a pH 7.2 isotonic saline and allow lenses to remain in solution while stirring for a minimum of 3 hours.
After hydration, lenses should be rinsed, autoclaved, and stored in the pH 7.2 buffered saline solution for packaging and sterilization.
Cabonate Buffer pH 8.2; 250 mOs • Borate Buffer pH 7.2; 295 mOs
NaCl 7.0 grams • NaCl 8.01 grams • NaHCO3 1.25 grams • H3BO3 2.47 grams • Na2B4O7 . 10H2O 0.14 grams
The weights for the buffered saline formulas are based on a 1 Liter Volume solution. The borate solution shows excellent performance through the sterilization process (autoclaving) and leaves the lenses free of residue.