Piggyback Applications in Modern Contact Lens Practice
BY EDWARD S. BENNETT, OD, MSED; ROBERT M. GROHE, OD; BRUCE W. ANDERSON, OD; MICHAEL J. LIPSON, OD; & LORETTA B. SZCZOTKA-FLYNN, OD, MS
In a recent forum on GP applications for post-surgical corneas on www.gpli.info, Drs. Robert Grohe and Loretta Szczotka-Flynn presented several interesting cases. Their discussion about piggyback lens systems was especially informative and included the following topics.
1. What patients benefit most from a piggyback combination? Piggyback combinations have their greatest applications in patients exhibiting irregular corneas (often post-surgical but also in advanced cases of keratoconus) in which a GP lens alone won't center well and/or the patient experiences persistent lens awareness. In particular, it's an alternative to a hybrid design in cases where the hybrid either fits too tightly or — due to its flexibility — results in significant residual astigmatism.
However, because of the complexity of a two-lens system, we recommend that you consider other contact lens corrective alternatives first for irregular cornea patients.
2. What lens materials and designs should you use? A hyper-Dk GP lens material such as Boston XO2 (Bausch & Lomb), Menicon Z (Menicon) or Fluoroperm 151 (Paragon Vision Sciences) is essential. The soft lens should be a silicone hydrogel material to allow sufficient overall oxygen transmission on an already compromised cornea. A higher-modulus material such as Night & Day (CIBA Vision) will minimize any resultant flexure. Also consider Acuvue Oasys (Vistakon), which essentially acts as a bandage while the GP lens base curve radius can be the same as the pre-piggyback design or as much as 1.00D flatter.
An alternative is to perform keratometry over the soft lens and select a GP base curve radius slightly steeper than the flat over-keratometry value. You can easily manipulate the GP lens fit by changing the soft lens material and design. If a steep central corneal apex exists, consider a low minus power soft lens. If an inferior corneal apex exists or the central cornea is very flat as a result of refractive surgery, a low-to-medium plus power soft lens can build up the central cornea to optimize the fitting relationship of the GP lens.
3. What care systems and patient education recommendations are important? Clear Care (CIBA) is FDA-approved for both GP and soft lenses and represents a viable option. Piggyback lens patients have also had success with Aquify MPS (CIBA). A GP cleaning and disinfecting solution such as B&L's Boston Simplus is important as well.
Instruct patients to rinse their GP lenses with saline (not tap water) and to thoroughly clean (in a back and forth motion in the palm of the hand) and rinse both lenses upon removal. This is especially important in higher risk cases in which immuno-compromised corneas may be more susceptible to sight-threatening infections.
Frequent use of rewetting drops can rinse away debris and rehydrate the soft lens. Rewetting drops can include Aquify Long Lasting Comfort Drops (CIBA), Blink Contacts (Advanced Medical Optics) or Complete Blink-N-Clean Lens Drops (AMO).
Finally, patients must replace the soft lens on a frequent basis — as prescribed or sooner if discomfort or a change in the GP fitting relationship occurs. CLS
Dr. Bennett is an associate professor of optometry at the University of Missouri-St. Louis and is executive director of the GP Lens Institute.
Dr. Grohe is in private practice in the Chicago suburbs and is on the faculty at Northwestern University Medical School in Chicago.
Dr. Anderson practices in Tampa, Fla., and is the director of the Contact Lens Clinics at the University of South Florida, College of Medicine, Department of Ophthalmology.
Dr. Lipson is a clinical assistant professor with the University of Michigan's Kellogg Eye Center. His practice is primarily contact lenses with a large percentage of specialty lens patients.
Dr. Szczotka-Flynn is an associate professor at Case Western Reserve University Dept. of Ophthalmology and is director of the Contact Lens Service at University Hospitals of Cleveland.