Fitting & Verification
Rigid Lens Verification

After receiving rigid lenses from the laboratory, the following parameters should be inspected for accuracy.

• Diameter
  
  
• Surface Quality and Edges
  
  
• Base Curve
  
  
• Power
  
  
• Thickness
  
  
• Blend
  
  
• Transition Zones

Diameter:
The lens diameter can be verified with a measuring hand magnifier, a diameter gauge, or one of the various types of projector inspection devices. Tolerance is within 0.05 mm.

Surface Quality and Edges:
Can be assessed utilizing a measuring magnifier, projector inspection device, or through the use of the slit lamp.

Base Curve: Most often measured utilizing a radiuscope. Base curves can also be measured using a keratometer with a special holder which allows the contact lens to be held horizontally while the keratometer remains in its normal position. Such a holder is called a Con-ta-chek. The base curve should be accurate to within 0.025 mm of specifications.

Power: Back vertex power is measured with a lensometer. Should be within 0.25 D of power specified with less than 0.12D of uncalled for astigmatism.

Thickness: Measured with a thickness gauge.

Blend & Transition Zones: May be examined through the use of a hand magnifier, projector inspection device, or slit lamp.

The measuring hand magnifier and projector inspection device are particularly useful since they can measure peripheral curve width, optic zone width, lens diameter, and surface quality.

The radiuscope is primarily designed to measure radius of curvature, but it can also function to assess the surface quality of a rigid lens. To help ensure accuracy when using a radiuscope or keratometer remember to first focus the eyepiece.

A slit lamp can also be useful as a lens inspection device when higher magnification is desired.

Hand Magnifier	Diameter Gauge
Projector Inspection Device	Radiuscope
Slit Lamp	Thickness Gauge