GP Insights

Piggybacking Scleral Lenses

By Gregory W. DeNaeyer, OD, FAAO

Scleral contact lenses have the distinction of successfully fitting eyes that have irregular corneas when all other design options have failed. In some cases, however, piggybacking a scleral lens onto a soft contact lens (Figure 1) is necessary to improve fit or function. In this column, I describe some typical situations where you may wish to consider this option.

Figure 1. Soft lens sandwiched between a scleral lens and the cornea.

Insufficient Vault

Fitting a scleral lens to completely vault a severely irregular cornea can be difficult to impossible. This is often the case when a patient has an ectatic cornea secondary to keratoconus or an isolated steep area at the host interface of a corneal button after a full-thickness corneal transplant. Fitting a somewhat larger scleral lens will allow for more sagittal depth to increase the vault, but other limiting factors, such as aperture size, may prevent this approach. In addition, many scleral lenses will decenter inferiorly, resulting in superior corneal touch, which can be difficult to correct. If there is no negative epitheliopathy related to the scleral touch, close observation may be satisfactory, but in some cases, piggybacking the scleral lens onto a soft lens may be necessary to avoid epithelial compromise.

Photophobia

Many patients who have severe ocular surface disease have increased sensitivity to light, despite being able to wear scleral lenses. Wearing sunglasses is a reasonable option for most patients, but some patients are sensitive to light indoors as well and may not want to compromise their vision or draw unnecessary attention to themselves by wearing sunglasses indoors. Another option for these patients is to piggyback a scleral lens onto a tinted soft contact lens (Figure 2). Of course, this would be for daytime activities and would have to be removed after dark, especially for driving.

Figure 2. Scleral lens piggybacked onto a soft, tinted lens.

Important Considerations

When considering piggybacking scleral lenses onto soft contact lenses, keep the following factors in mind:

• If a cornea is so irregular that a standard, soft contact lens may not fit properly, consider a specialty design soft lens.
• GP care solutions can negatively interact with a soft contact lens. Therefore, prescribe a hydrogen peroxide- or alcoholbased care system for cleaning and disinfecting the scleral GP.
• Daily disposable lenses have a number of advantages over standard planned replacement lenses, including minimizing allergen buildup and deposits and eliminating the need for soft lens cleaning and disinfection.
• If hypoxia and neovascularization are concerns, consider using a silicone hydrogel lens to maximize oxygen permeability.

Optimal Wearing Experience

Scleral GP lenses can often be used to manage the most severe corneal irregularities or ocular surface disease, but in some cases, piggybacking the scleral lens on a soft contact lens will improve the patient's wearing experience. CLS