Although rare, microbial keratitis (MK) is an acute and potentially sight-threatening risk for patients wearing scleral lenses. The SCOPE (Scleral Lenses in Current Ophthalmic Practice Evaluation) survey, which represented more than 84,000 scleral fits, reported less than 1% of reported scleral lens-associated MK (Schornack et al, 2016). There had been one published isolated case of Acanthamoeba keratitis (AK) in a scleral lens patient who had ocular graft-versus-host disease (Farhat and Sutphin, 2014). Risk factors for this patient included dry eye, use of autologous serum, potential tap water exposure, and long-term systemic corticoid steroid use. Acanthamoeba is a ubiquitous, free-living organism that can present in an active trophozoite or inactive cyst form. It is able to attach to contact lenses, cases, and the corneal epithelium. Most AK is related to soft contact lens wear and occurs at a rate of 1 to 2 million cases per year (Verani et al, 2009). The most severe cases can require months of treatment and the possibility of needing a corneal transplant.

A more recent publication reported an alarming case series of three keratoconus patients wearing scleral lenses who developed AK (Sticca et al, 2018). The first was an 8-year-old child whose parent rubbed and rinsed his lens with multipurpose solution but stored the lens overnight in saline. The second was an adult female who had a history of showering while wearing the lens but stored her lens overnight in multipurpose solution without a rub step. The last patient was an adult male who had a history of water exposure with lens wear, including showering and swimming. He stored his lenses in multipurpose solution without a rub step and topped-off the solution. The common risk factor was the use of a commercially available 500ml bottle of nonpreserved saline to fill their lenses prior to application.

Discussion

AK has been a rare event for corneal GP lens wearers despite the fact that many patients use tap water either as directed when using two-step GP cleaning and disinfection systems or improperly by rinsing lenses with water prior to application. It is possible that scleral lens wearers could be at additional risk compared to corneal GP wearers because contaminated filling solution is trapped behind the bowl of the lens (Sticca et al, 2018). Without education, many patients do not understand the inherent risk of water exposure with contact lens use because in everyday activities, water is a necessary and safe component of life.

Another potential risk factor for AK for scleral users is that the epithelial surface could be compromised secondary to the underlying condition that requires use of scleral lenses (e.g., ocular surface disease), from hypoxia, or from microtrauma from a poorly fit lens.

Previous long-term GP lens wearers might be most at risk because decades of potential noncompliance will continue if they transition to scleral contact lenses. Patients must be educated about the strict avoidance of water exposure. Additionally, rubbing and rinsing contact lenses with approved solutions is needed to remove attached organisms prior to soaking. Topping solutions off is never acceptable. Prescribe only single-use saline to avoid contamination of filling solutions. Finally, plungers should be kept clean and sterile, without water exposure that could accumulate within the bulb.

Education and strict avoidance of water is required to reduce the risk of this devastating event. CLS

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