Post-lens tear reservoir fogging occurs when debris accumulates between the scleral lens and the cornea, which may occur after minutes to hours of lens wear.1,2 There are numerous causes of scleral lens fogging including increased tear exchange and accumulation of tear debris in the lens reservoir, increased mucin production from rubbing of the conjunctival tissue, accumulation of protein and lipid deposits on the front surface of the lens, and corneal edema.3 Fogging is typically associated with debris either on the front surface or in the post-lens fluid reservoir.
However, symptoms of fogging are similar despite the cause. Corneal edema should be ruled out immediately by removing, cleaning, and reapplying the scleral lens. If a patient experiences rainbows around lights (Sattler’s veil) or if vision continues to be blurred, evaluate the cornea for corneal edema. There are different types of post-lens reservoir fogging such as mucous debris, fogging associated with atopic disease, and meibomian debris. The literature has demonstrated that post-lens tear debris consists of a high concentration of lipids; complications related to tear reservoir clouding are especially common in those who have ocular surface disease.4
A recent publication evaluated factors associated with patient-reported midday fogging in established scleral lens wearers.5 Midday fogging was self-reported in 64 (25.8%) patients in 248 survey respondents. Midday fogging was not correlated with demographic characteristics (age, sex, race/ethnicity), scleral lens indications, mean lens diameter (P = 0.30), haptic design (P = 0.29), use of a daily cleaner (P = 0.12), disinfection/storage solution used (P = 0.71), or filling solution (P = 0.65). Associated redness or irritation was more commonly reported in patients who reported midday fogging compared to those who did not experience midday fogging (P = 0.03). The authors concluded that if inflammatory mediators are elevated in the post-lens fluid reservoir of patients who have midday fogging, ocular redness or irritation associated with scleral lens wear suggests that ocular surface inflammation may be contributory.
Muriel Schornack, OD, lead author of the study, explained that although the study’s methodology does not allow for robust examination of the precise causes of midday fogging, the data do raise some questions about some of practitioners’ long-held assumptions of the origins of this phenomenon. While the authors cannot state that factors such as indication for scleral lens wear, lens diameter, or haptic design have no impact on midday fogging, they can state that fogging may be observed with any indication. In addition, she explained that the use of lenses of a particular diameter or haptic design cannot completely eliminate midday fogging.
Many thanks to Dr. Schornack for her excellent insights.
McKinney A, Miller W, Leach N, Polizzi C, van der Worp E, Bergmanson J. The Cause of Midday Visual Fogging in Scleral Gas Permeable Lens Wearers. Invest Ophthalmol Vis Sci. 2013 Jun:54:5483.
Carrasquillo, KG, Lipson MJ, Ezekiel DJ, Johns LK, Barnett M. Scleral Lens Complications and Problem Solving in Barnett M, Johns LK, eds. Contemporary Scleral Lenses: Theory And Application. United Arab Emirates: Bentham Science Publishers, 2017. Pages 395-404.
Walker M, Morrison S, Caroline P, et al. Laboratory analysis of scleral lens tear reservoir clouding. Poster presented at the 2014 Global Specialty Lens Symposium, Las Vegas, Jan. 2014.
Schornack MM, Fogt J, Harthan J, et al. Factors associated with patient-reported midday fogging in established scleral lens wearers. Cont Lens Anterior Eye. 2020 Mar 20. [Epub ahead of print]
Dr. Barnett is a principal optometrist at the University of California Davis Eye Center, 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, Alden Optical, Allergan, Bausch + Lomb, Bruder, Contamac, CooperVision, EveryDay Contacts, Johnson & Johnson Vision, Ocusoft, Paragon Bioteck, RaayonNova, ScienceBased Health, SynergEyes, Tangible Science, and Visioneering Technologies.