For anyone who has fit specialty lenses long enough, scleral lenses have quickly become a first line of defense for fitting irregular corneas. And, if you have been fitting scleral lenses for some time, you know that they are not the panacea of the specialty lens world; they have cons as well. While they can initially be comfortable for a patient, scleral lenses can be significantly higher in cost. For some patients who have insurance barriers or who do not have a covered benefit for some reason, scleral lenses may be cost prohibitive. Another reason why patients may have issues with sclerals is that while they may love them, sclerals are susceptible to breakage; my guess is that this happens more frequently than with other specialty lenses such as GP or hybrid lenses. Finally, some may not like the time required to apply and remove scleral lenses, not to mention having to use plungers, solutions, etc.

So what are our options for these patients? One is the tried-and-true gold standard corneal GP lenses. And, if those don’t work, consider a piggyback modality.

Presently, piggyback systems are comprised of a commercially available soft silicone hydrogel lens fit under a corneal GP lens. Historically, low oxygen permeability was a deterrent due to problems with corneal hypoxia and vascularization with piggyback systems. Fortunately, concerns about oxygen permeability are a thing of the past given advancements in contact lens technology. Of note, some corneal specialists are still opposed to the piggyback modality due to concerns of hypoxia and mechanical issues over a penetrating keratoplasty.

When to Piggyback Lenses

Piggyback lenses are most commonly considered for existing corneal GP lens wearers who start to experience lens discomfort. This can be due to a variety of reasons such as general lens awareness or discomfort, lens decentration, or lens bearing on the cornea. For some fitters, the soft/GP combination can be intimidating with regard to choosing the “correct” soft lens or to the fitting of the GP parameters after the soft lens is placed on the eye.

Common Concerns

During my residency, I was taught to use a –3.00D soft lens that would act as a carrier. The reason for this is because the thin center is ideal for oxygen permeability (Walsh et al, 2001; Walsh et al, 2003; Walsh et al, 2007). Additionally, the periphery is thicker by design, which acts to hold or center the GP lens in place (Romero-Jiménez et al, 2015). Finally, the negative power can, in some cases, reduce the needed power of the GP lens (Romero-Jiménez et al, 2015). Some fitters may choose to offset an oblate or flat cornea with a higher-plus lens in which the thickness of the lens will fit into the contour of the cornea. Once the soft lens is in place, I use the patients’ habitual lens over the soft lens to assess the fit and follow common GP fitting guidelines. If you have it available, high-molecular-weight fluorescein can be used to look at the fitting of the GP lens without compromising the soft lens. Because there is less risk of the GP lens rubbing on the cornea, I find white light suitable.

Of course, one drawback of this system is that patients may have to use two different care solutions, but this can be circumvented by recommending a hydrogen peroxide-based solution. It also will clearly take patients a bit more time to apply and remove their lenses, and the cost of the soft lenses should also be a consideration. Regardless, don’t fear this “older” technique as a suitable option for your patients. CLS

For references, please visit www.clspectrum.com/references and click on document #311.