OTHER LENS DESIGNS;

A. PIGGYBACK TYPES

1. Piggyback
        • Fit steep soft lens and then perform over-K's and fit RGP lens based upon over-K's
        • Fit high Dk RGP
        • Benefits: Comfort & Centration
        • Problems: Steep enough soft lens, bubble between soft & RGP, edema, care system

2. Soft Perm (Wesley-Jessen)
        • Combination RGP (styrene) and 25% soft blanket
        • Preferable to piggyback
        • 14.3mm OAD; 8.0mm RGP; 7.0mm OZD
        • Available as steep as 6.5mm BCR
        • Benefits same as piggyback
        • Problems: tight fit, difficult to remove (tearing), edema

3. Flexlens (Paragon Vision)
        • Soft lens with circular cutout section for an RGP lens to fit (see attached information)
        • Advantages & disadvantages same as other designs

B. SPHERICAL DESIGNS

1. Rose K (Lens Dynamics)
        • Small lens design with 6.3-6.5mm OZD and 5-6 blended PC's designed mathematically; flat, standard and steep edge lift designs (flat often preferable)
        • Typically provides good centration
        • Expensive $75 for warranted with 2 exchanges w/in 90 days.
        • Fitting information attached
        • Boston ES material

2. Soper Cone
        • Traditional design: one steep pc
        • Still used by many labs

3. Ni-Kone (Lancaster, PA)
        • "Tri-Base Curve" philosophy for centration purposes