By John Rinehart, OD
I. Fitting Technique Options
- Diagnostic/Overnight Diagnostic
Empirical fitting involves providing Ks and Subjective (sometimes topography) to the lab or lens designer.
Diagnostic/Overnight Diagnostic may require evaluation of fluorescein pattern on the open eye. Overnight diagnostic fitting where the best initial fit is determined though fluorescein pattern evaluation and/or analysis of topography. After one night of wear, prefit and current topography are compared to determine where the lens centered overnight.
Topography-based systems determine the initial lens from the corneal topography provided.
Most systems are a combination, because at some point they incorporate the use of topography.
Any discussion on the advantages of each technique or a particular design?
- Decentered Lenses: High, Low, Lateral
- Central Islands and False Central Islands
- Not covered tonight due to time constraints:
- Physiological Problems: corneal staining
- Lens Adhesion/Binding
III. Basic Lens Change Options
- Increase Sag
- Decrease Sag
- Increase or Decrease Diameter
On left treatment zone decentered high. What was changed to get to topography on the right?
Cause? Solution? (Topography courtesy of Randy Kojima of Precision Technology Service.)
How do you fix this problem? (Topography courtesy of Jim Reeves, OD)
Central Island/Incomplete Treatment Over the Corneal Apex
What are the options to fix this problem?
False Central Island
How do you differentiate this from a “true” central island?
What lens changes are necessary to remedy this problem?