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3-2 |
Introduction |
In part 3, Fitting & Verification, we'll be applying that which we've studied in the
previous two sections about lens materials and designs and optical principles toward the
actual fitting of rigid and soft contact lenses. How big should a contact lens be? When
should it be fit on K, or steeper or flatter than K? What about its thickness and peripheral curves? These questions will be addressed in this section.
Although PMMA lenses are rarely fit today, the principles one needs to apply in fitting
them are fundamental to all rigid lenses and will therefore be covered in this session.
We'll begin with a discussion of palpebral lenses as well as larger lenses with wide
peripheral curves. The general characteristics, advantages, and disadvantages of each
will be discussed. This will be followed by methods and procedures for selecting base
curve, diameter, optical zone width, peripheral curves, and thickness through the use of
diagnostic lenses, nomograms and charts. Examples and practice exercises are included.
Dynamic flourescein patterns are used to assist in the evaluator of the fit of rigid contact
lenses. How and why this is accomplished is covered in the second half of Part 3. We'll
illustrate flourescein patterns of a spherical base curve on a spherical cornea, and
spherical base curves on a toric cornea are presented. Astigmatism with the rule, against
the rule, and oblique will be discussed and observed. Soft lens evaluation is then covered
to include fitting goals and the characteristics of a good fitting soft lens.
Part 3 concludes with a presentation of rigid and soft lens verification techniques to
include the use of the measuring hand magnifier, diameter gauge, projector inspection
devices, slit lamp, radiuscope, thickness gauge, lensometer, and profile analyzer. We'll
see that soft lenses too can be verified through the use of a hand magnifier, plastic templates, a soft lens analyzer, and the use of a water cell.
This section will conclude with a thirty-four question practice test based on the material covered.