CASE STUDY - Dr. Quinn

Hx: 22-year-old waitress interested in contact lenses

Refraction:
     OD -1.00 - 3.00 x 180
     OS -2.00 - 2.25 x 175

K's:
     OD 41.00 @ 180; 44.00 @ 090
     OS 43.00 @ 175; 45.00 @ 085

Treatment options:
     1. Toric soft contact lenses
     2. Spherical GP lenses
     3. Toric GP lenses

Diagnostic lens applied OD:
     Base curve: 8.03mm (42.00 D)
     OAD/OZ: 9.2/7.8
     Power: -2.00
     ct: .16

Spherical diagnostic lens demonstrates poor centration; therefore elected to pursue toric GP fit. Where to start?

All maintain a 0.75 difference in fitting relationship between horizontal and vertical meridians to mimic fitting the "ideal" cornea.

Order:
     BC: 41.00 (8.23mm)/43.25 (7.80mm)
     BVP: -1.00/-3.25
     Difference in base curve (D): 2.25 D
     Difference in lens powers: 2.25 D

Conclusion: Spherical Power Effect (SPE) Design

• Difference in base curve (D) is equal to the difference in lens power (in air)
• Provides: fit like a toric base lens with power effect of non-flexing sphere
• Advantage: lens can rotate without compromising vision!