This article was originally published in a sponsored newsletter.

Poor scleral lens surface wettability affects the quality of the anterior lens surface and may present with deposits or a greasy front surface of the lens.¹ Many factors can affect poor surface wettability such as residue due to manufacturing; tear film quality, quantity, and chemistry; blinking; conditioning solution; and lens material.¹ Individuals who have any type of ocular surface disease or severe dry eye (e.g., Sjögren’s or graft-versus-host disease) are more prone to poor surface wettability and require treatment to improve wettability of the anterior surface of a scleral lens.
 
Various treatments have been suggested to improve scleral lens wettability. Plasma treatment creates a hydrophilic rigid surface with the ionized oxygen plasma to improve lens wettability (or the decrease contact angle) by 40% and decrease bacterial adhesion.¹ Yet, plasma treatment wears off with time. Polyethylene glycol polymer coating applied after plasma treatment can improve lens wettability (or the decrease contact angle) by 50% and lessen lipid and protein deposits.¹
 
Alternative methods to improve wettability are lens removal, cleaning and reapplication, or on-eye surface cleaning with a moistened cotton swab or plunger. If none of these methods improve wettability, a soft daily replacement contact lens may be applied on the front of the scleral lens to improve scleral lens wettability. This method may be referred to as a “reverse piggyback” system.

A recent study compared the amount of corneal edema with reverse piggyback scleral lens wear to standard scleral lens wear.² Ten healthy individuals who had normal corneas with a mean age of 22 years were included in the study. Optical coherence tomography was used to measure the thickness of the cornea and the thickness of the fluid reservoir prior to and after 90 minutes of either standard scleral lens wear or reverse piggyback scleral lens wear. Identical diagnostic scleral lenses were used for both groups (Kerectasia Alignment Tangent Torus lenses, hexafocon A, Dk 100 × 10¹¹ [cm²/s][ml O₂ /ml × mmHg], Capricornia Contact Lenses). In the reverse piggyback group, the soft daily replacement contact lens applied to the lens surface was Dailies Total 1, delefilcon A, Dk 140 × 10^-11 (cm²/s)(ml O₂/ml × mmHg), Alcon.
 
Central corneal edema was comparable between the reverse piggyback and standard scleral lens groups after correcting for minor variations in the initial central fluid reservoir thickness. Reverse piggyback scleral lens wear may be used to alleviate poor front-surface scleral lens wettability or during diagnostic scleral lens fitting to correct residual refractive error.
 
The limitation of this study is that individuals who require a reverse piggyback system more commonly have concomitant and chronic ocular surface disease or severe dry eye, require a longer duration of scleral lens wear, and may be older in age.
 
Additional research to evaluate reverse piggyback scleral lens systems with different soft and scleral lenses in ocular surface disease may be beneficial to determine the indications for long-term scleral lens wear.

REFERENCES
1. Barnett M, Courey C, Fadel D, et al. CLEAR - Scleral lenses.Cont Lens Anterior Eye. 2021 Apr;44:270-288.

2. Bliss VH, Branjerdporn N, Ooi PJ, et al. Corneal oedema during reverse piggyback scleral lens wear.

Melissa Barnett, OD, FAAO, FSLS, is the Director of Optometry at the University of California, Davis in Davis, specializing in anterior segment disease and specialty contact lenses. She is the past president of the Scleral Lens Education Society. She is an advisor to and/or has received honoraria or travel expenses from AccuLens, Alcon, Allergan, Bausch + Lomb, Bruder, Contamac, CooperVision, Johnson & Johnson Vision, Ocusoft, ScienceBased Health, Shire, SynergEyes, Tarsus, and Visus Therapeutics.