LOW ASTIGMATISMFitting and Evaluation
Jessica Conroy, OD, FAAO
Spherical GP (1)
Utilize sodium fluorescein (NaFl) and cobalt blue filter with a biomicroscope to evaluate the lens-to-cornea fitting relationship.1
- Utilization of a Wratten Filter will help to highlight the NaFl pattern.
- Alignment Fitting Relationship is observed when the lens evenly contours the cornea. Evaluate the lens using the ABC method.
- A: apical clearance or alignment
- B: mid-peripheral bearing
- C: edge clearance
Front Toric GP (1)
Perform the NaFl evaluation for a front toric GP in the same way as a spherical GP.
Due to lens mass, the lens will most likely decenter inferiorly.
When evaluating a front toric GP, one must also note the location/rotation of toric markers on the front surface of the lens.
References
- Bennett ES, Sorbara L, Kojima R. Gas Permeable Lens Design, Fitting, and Evaluation. In Bennett ES, Henry VA. Clinical Manual of Contact Lenses, 5th ed. Wolters Kluwer, Philadelphia, PA, 2020:134–185.