Reader and Industry Forum
Piggybacking: A New Approach for Scleral Lens Fogging
BY DAVID L, KADING, OD, FAAO
What happens when material meets material? Piggyback contact lens systems have been used for decades; soft lens bases can aid with comfort and fit for GP wearers and were once prescribed on a regular basis.
Not much has been written about piggyback lenses in the last 10 years because of the continual introduction of improved contact lens designs and options for patients. Custom soft lenses, hybrid lenses, and sclerals have saturated our market, giving us many more options than just corneal GP or GP piggybacked designs.
The Evolution of Piggybacking
But let’s consider the innovations that piggyback designs brought to our marketplace. First and foremost, piggyback lenses are used to create a gasket between the ocular surface and GP lenses. With edge designs and altered corneal shapes complicating GP fitting, a piggybacked soft lens provides a barrier between these sensitive areas, which ultimately improves comfort for many patients.
More complex piggyback lenses were introduced as the technology and utilization advanced. Soft lenses were developed that include a groove into which a GP lens can rest. This results in a better chance for the GP lens to center upon the eye in cases of irregular corneal and subsequent corneal-soft lens topography. Although used sparingly, this advancement is very innovative.
High-powered plus or minus soft lenses can be utilized to alter the fitting surface so GP lenses are easier to fit. For example, in patients who have significant corneal steepening because of conditions such as keratoconus, high-powered minus soft lenses can create a flatter cornea-soft lens topography shape. For patients who have flattened central corneas due to refractive or transplant surgery, high-powered plus lenses may be used to create a more steepened topography, thus making for an easier GP fit.
Piggybacking Scleral Lenses
Which leads us to the future of piggyback lenses. Much has been said about fogging with scleral lenses. We still have many uncertainties related to why fogging happens and what causes the corneal tear film interaction that produces this effect. Many scleral lens fitters find that reducing the scleral lens sagittal depth can reduce the fogging effect, but the general consensus remains that the scleral lens should not rest on the corneal tissue if at all possible.
Enter piggyback scleral lens fitting. Although we have much to learn about this concept, discussions on the topic have been initiated between myself and several top scleral lens experts. We have begun research and utilization of this process in our own offices and at Pacific University, and we are anxious for additional information to become available. With the same theory as GP and soft lens interaction, we theorize that the soft lens can take the place of the tear film chamber with the hope of keeping the ocular surface safe while reducing the chamber for fogging to occur.
Although this theory has yet to be vetted in the larger scleral lens community, keep your ears open for additional ways in which we can use piggyback lenses for the betterment of our patients’ vision and comfort. CLS
Dr. Kading owns the Specialty Dry Eye and Contact Lens Center in Seattle. He is the co-owner of Optometric Insights with Dr. Mile Brujic. He has received honoraria for consulting, performing research, speaking, and/or writing from Alcon, Allergan, Bausch + Lomb, CooperVision, Oculus, Ocularis Pharma, RPS, Shire, TearScience, Valeant Pharmaceuticals, Valley Contax, Zeiss, and ZeaVision. Follow him on Twitter @davekading.