Wet Cell

Soft Contact Lens Measurement and Inspection Instruments

Sterling supplies a range of instruments for the accurate measurement and inspection of soft contact lenses. All instruments use the best-practice method of immersing the soft contact lens in a saline solution, using a wet cell for lens analysis.

Operating Principle

The lens diameter is measured and the surface is inspected as follows:

The soft contact lens is positioned on a 10mm diameter cylinder. A probe is raised through the center of the cylinder via a micrometer screw and hand operated dial (BCOR scale). The lens diameter is viewed on a projection screen. The BCOR value is read from the BCOR scale.

A graticule (i.e. grid lines in the focal plane) is mounted within the wet cell and is projected along with the plan view of the soft contact lens. This method ensures accurate measurement of the lens diameter, irrespective of magnification at the viewing screen. The smallest division is 0.1mm.

JCF is available with or without a saline filtration system.

JCF/F offers a peristaltic pump mounted on the cabinet, which feeds saline back to the cell via a renewable cartridge filter. The pump system removes particles from the saline, to ensure that the image of the contact lens in the wet cell is not affected by these.

Both JCF and JCF/F can be fitted with the TC20i temperature control system.

Benefits:

• Easy- to-use wet cell system
• Measures all 3 critical parameters of soft contact lenses to +/- 0.05mm
• Inside radius measurement 6.5mm to 9.5mm
• Center thickness measurement 3.5mm to maximum
• Overall diameter measurement 6.0mm to 16.0mm
• Plan view magnification X16
• Profile view magnification X19
• Dual projection system allows both lens profile and full edge inspection
• Upper and lower surface inspection by focusing through lens
• Optional saline filtration system
• Optional temperature control of wet cell

TC20i is a consistent and accurate solid state-cooling instrument, using the reliable Peltier effect. A temperature probe using an NTC thermistor is immersed in the wet cell, and the saline is heated or cooled to the required temperature. It is then maintained at that temperature at all times. The default temperature is 20°C, but the optional temperature settings range from 15 to 38°C for special needs or research and development applications. Filters for these units are available from Sterling.

Benefits:

• Saline cooling for consistent 20°C for normal operation
• Temperature constant to +/- 0.3°C
• Avoids dimensional variations due to temperature change
• Warming of saline in winter conditions
• Heating or cooling of saline solution to required temperature (15 to 38°C) for R&D and other applications
• Temperature control unit is separate and can be removed/switched on or off as required

The Chiltern is an economical and cost-effective version of the JCF, which operates on the same principles of measurements.

It cannot be fitted with saline filtration or temperature control, and the design of the optics is simplified to reduce costs.

Nevertheless, it is an accurate and useful instrument for checking soft contact lenses, and is used by both practitioners and manufacturers for a variety of inspection tasks.