GP lens eye Rounds

LOW ASTIGMATISM: Fitting and Evaluation

Jessica Conroy OD, FAAO

Spherical GP

• Utilize sodium fluorescein (NaFl) and cobalt blue filter on biomicroscope to evaluate lens-to-cornea fitting relationship²
  • Note: Utilization of a Wratten Filter will help to highlight the NaFl pattern
• Descriptions²
  • Areas where NaFl is present in the tear layer appear to be green
  • Areas where NaFl is absent (or is too thin to detect) appear black
• Alignment Fitting Relationship: observed when lens evenly contours cornea
  • Center: light, even tear pooling
  • Mid-Periphery: thin, even, circular band of bearing
  • Edge: even tear pooling to allow for sufficient tear exchange

Front Toric GP²

• NaFl evaluation same as spherical GP
• Due to lens mass, the lens will most likely decenter inferiorly
• When evaluating, must also note location/ rotation of toric markers on front surface

Sources

1. 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.