Article

THE SCLERAL LENS VAULT

SURFACE FUNDAMENTALS

A majority of scleral lens education and clinic time is spent on the process of fitting and designing scleral lenses. A proper fit is needed for success, but so is a clean and clear lens surface. The clinical challenge is to properly match GP materials with patients’ anterior ocular surface environment. Unfortunately, the GP material polymers that allow oxygen permeability have hydrophobic properties that can disrupt the function of the lenses. Poor wetting and deposits can negatively impact scleral lens comfort and performance (Figure 1).

Figure 1. A non-wetting, deposited scleral lens.

Surface Treatments

A first step in ordering a scleral contact lens is choosing a GP material from the available selection of your preferred manufacturer. Healthy patients who do not have ocular surface disease (OSD) will most likely be able to wet most hyper-Dk materials. For those patients, choose a material with Dk of approximately 100 for maximum lens performance or choose a higher-Dk material if hypoxia is a concern.

Most laboratories routinely plasma treat finished scleral lenses for improved initial performance. Oxygen plasma is able to super clean the lens surface of organic residues that result from manufacturing. Plasma treatment also imparts surface ionization that improves initial wettability. Scleral lenses that have been plasma treated should be stored wet, and abrasive cleaners should be initially avoided because they negate the increased wetting properties.

A 90% water polyethylene glycol (PEG)-based polymer, which can be coated onto approved GP materials, creates a highly wettable surface that resists protein and lipid deposition. Most U.S. labs offer this optional treatment upon request. Patient candidates of this treatment include those who have a known history of GP wetting difficulties or heavy deposition, dry eye patients, and those who have a history of poor adaptation to GP lenses.

Only new lenses after plasma treatment can undergo the PEG coating. After application, the lenses must be stored wet in an approved multipurpose disinfecting solution. The PEG coating will be disrupted with the use of alcohol-based or abrasive cleaners as well as with exposure to water. It is unknown how long the PEG coating lasts, but recoating a previously worn lens is not an option due to contamination concerns. One PEG manufacturer has announced the future availability of a specific cleaner and booster solution that will complement the PEG coating.

Deposition and Replacement

The scleral lens surface should be continually monitored for wetting and deposition. Non-wetting lenses may need to be replaced. Extra strength cleaners should be added if lipid or protein deposition is observed. Surface deposits contribute to poor vision and comfort. Additionally, lens replacement is required for any deposits that cannot be removed with cleaners or in-office polishing. Older lenses can develop micro-scratches or crazing (Figure 2). Crazed lenses contribute to reduced vision and surface performance and should be replaced.

Figure 2. A scleral lens with crazing.

Practitioners must be proactive about keeping the surface of a scleral lens pristine to ensure maximum comfort and vision. Ideally, scleral lenses should be replaced before irreversible deposits or scratching hinders lens performance. CLS