PERHAPS THE BIGGEST IMPACT that modern scleral lenses have had on specialty lens fitting is dramatically improved stability and comfort for keratoconus patients who require GP lenses for improved visual performance. In fact, their increased use has been demonstrated to reduce the need for corneal transplants (Koppen et al, 2018). However, there are still select patients who aren’t successful with scleral lenses. The following two cases are keratoconus patients who failed with scleral lens use but were then successful with a piggybacked corneal GP lens fit (Figure 1).

CASE #1

A 63-year-old female keratoconus patient reported for specialty contact lens fitting. She had a history of prior penetrating keratoplasty on her right eye. The patient had been wearing corneal GP lenses. She was never able to achieve a comfortable fit of her right eye and was advised to be refit with a scleral lens. Unfortunately, despite maximizing the oxygen transmissibility of her right scleral lens, she developed clinically significant corneal edema.

The patient was advised to piggyback her right 9.6mm corneal GP lens (hexafocon A) on a daily disposable silicone hydrogel lens (narafilcon A), base curve (BC) 8.5mm, power –0.50D (Figure 2). The lens combination fit well and there was mild movement with blinking. The patient achieved comfortable wear without complications.

CASE #2

A 39-year-old female keratoconus patient was fit with scleral lenses for visual improvement. Unfortunately, this patient couldn’t successfully apply a scleral lens to either eye. She was refit into 11.5mm intralimbal GP lenses (hexafocon A) that were piggybacked on silicone hydrogel lenses (narafilcon A), BC 8.5mm, power –0.50D for improved comfort.

She was successful with piggybacking for approximately two years. However, she then started wearing her GPs without the soft lenses because she had adapted to the corneal lenses and no longer required piggybacking.

RECOMMENDATIONS FOR PIGGYBACKING CORNEAL GP LENSES

Start by fitting the patient with a corneal GP lens. Larger-diameter designs will generally move less, which will help with stability and comfort. If the patient doesn’t adapt well after the lens is fit, then piggyback the GP lens on a soft lens with a low power.

Daily disposables are the best option for most patients, as they simplify the care regimen. A silicone hydrogel lens will maximize transmissibility, reducing hypoxic stress. Daily disposables with the highest sagittal depth will likely be necessary for keratoconus patients.

For help determining which lenses have the highest sagittal depth values, reference “Variation in sag values in daily disposable, reusable and toric soft contact lenses” (van der Worp et al, 2021). This paper contains helpful tables that list the sagittal depth values of available daily disposable lenses. Severe keratoconic eyes might require a custom soft lens to reach higher amounts of sagittal depth beyond that of branded daily disposables. Consider prescribing a hydrogen peroxide care system for the GP lens to avoid interaction between the higher viscosity GP multipurpose products and the soft lens.

REFERENCES

1. Koppen C, Kreps EO, Anthonissen L, Van Hoey M, Dhubhghaill SN, Vermeulen L. Scleral Lenses Reduce the Need for Corneal Transplants in Severe Keratoconus. Am J Ophthalmol. 2018 Jan;185:43-47. 

2. van der Worp E, Lampa M, Kinoshita B, Fujimoto MJ, Coldrick BJ, Caroline P. Variation in sag values in daily disposable, reusable and toric soft contact lenses. Cont Lens Anterior Eye. 2021 Dec;44:101386.