Meet Mr. Crusty

There are a couple of things happening in the very “crusty” scleral lens. A scleral lens, made from rigid GP material, requires regular cleaning and disinfection just like corneal GPs. The Scleral Lenses in Current Ophthalmic Practice (SCOPE) Study found in a survey of 989 practitioners that 61% recommended hydrogen peroxide for cleaning and disinfection, 54% prescribed a storage/conditioning solution specific to GP material, and 49% prescribed a multipurpose rigid GP solution.¹

The study also asked clinicians their recommendation regarding rinsing lenses with tap water. Eighty-two percent said they never recommended tap water, and 9% responded with “rarely.” The associated risk of possible contamination with Acanthamoeba is the concern. A study done in Korea found that five (4.2%) cases out of 120 were contaminated with Acanthamoeba.² In the study, 207 samples of domestic tap water showed the 46.8% contained free living amoeba (FLA) and 7.7% were specifically Acanthamoeba.

Some patients benefit from the addition of a polyethylene-glycol (PEG) surface treatment of the lens applied by the laboratory at the time of manufacture. A study released in 2021 found significant improvements in lens comfort, reduced corneal staining, fewer complaints of foggy vision. and increased tear break-up time (TBUT).³

The second issue in this case is the complete loss of central clearance where the lens is now resting on the cornea. We can see that this eye has undergone radial keratotomy (RK), which is the third leading indication (after keratoconus and pellucid marginal degeneration) for scleral lens fitting.¹ Numerous studies have shown that lenses lose central clearance (“settling”) over time. One found that lenses 16.5mm in overall diameter (n = 15) settled an average of 76 microns (± 8µm) over an eight-hour period.⁴ Seventy-five percent of the settling occurred in the first two hours.⁴ Other studies, with lenses from various manufacturers, found rates of settling over eight hours varied as well (e.g., 113.7µm, 133.7µm, and 88.1µm).⁵ With this in mind, when ordering, the recommendation is to build in enough vault to account for the lens sinking into the conjunctiva over time.⁶

1. Schornack M. The SCOPE Study: An Overview. Contact Lens Spectrum. 2017 Dec;32:25-28,30,31.
2. Jeong HJ, Yu HS. The role of domestic tap water in Acanthamoeba contamination in contact lens storage casers in Korea. Korean J Parasitol. 2005 Jun;43:47-50.
3. Mickles C, Harthan J, Barnett M. Assessment of a novel lens surface treatment for scleral lens wearers with dry eye. Eye Contact Lens. 2021 May 1;47:308-313.
4. Vincent S, Alonso-Caneiro D, Collins MJ. The temporal dynamics of miniscleral contact lenses. Central corneal clearance and centration. Cont Lens Anterior Eye. 2018 Apr;41:162-168.
5. Kauffman MJ, Gilmartin CA, Bennett ES, Bassi CJ. A comparison of the short-term settling of three scleral lens designs. Optom Vis Sci. 2014 Dec;91:1462-1466.
6. van der Worp E. A Guide to Scleral Lens Fitting (2^nd. Ed). Pacific University- Common Knowledge. Pacific University Libraries. Available at commons.pacificu.edu/work/1c04131a-7e30-4ccb-9ce5-6bee90360f3d . Accessed Sep. 28, 2022.