Translating Bifocals

Fitting

• Follow recommended fitting guidelines; these lenses are typically fit slightly flatter than "K" and are intended to position on or close to the lower lid due to the prism incorporated in the lens
   
• Have, at minimum, one diagnostic fitting set of these lenses; for recommendations, call your CLMA member laboratory
   
• Good candidates:
• Critical vision demand
• Any add requirement
• Lower lid positioned near to or slightly above lower limbus
• Normal or tight lower lid tension
• Lens positions on or near the lower lid and moves no more than 1mm with the blink. Photo shows a Good Bifocal Fit.
   
• The seg line is, in most designs, positioned at or near the lower pupil margin in straight ahead gaze
   
• The lens should shift upward or translated with downward gaze such that, at minimum, one-half of the near zone is in front of the pupil. This can be observed with the slit lamp while pushing up the upper lid.

Problem-Solving

• Patient reports blur at distance; rule out:
• Lens is picked up too high
• Lens is too small (does not adequately cover pupil); therefore, increase diameter
• Seg height is too high

• Patient reports blur at near; rule out:
• Seg height is too low
• No or intermittent translation
• Excessive lens rotation
• Patient drops head (not eyes) to read

 
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