Fluid Reservoir Characteristics in Established Scleral Lens Wear, Part II: Evaluation of Tear Exchange and Midday Fogging

OBJECTIVES: Tear exchange is less robust with scleral lenses compared to other modalities. This study evaluates tear exchange with scleral lens wear and examines relationships between tear exchange and optical density of the fluid reservoir and patient-reported midday fogging in established scleral lens wearers. METHODS: Participants reported if they experienced midday fogging. Tear exchange was evaluated by observing sodium fluorescein uptake into the post-lens fluid reservoir after 10 seconds, and 1, 2.5, and 5 minutes. Optical density of the fluid reservoir was measured using Scheimpflug imaging. Sensitivity, specificity, and negative and positive predictive value (NPV and PPV) of tear exchange as a predictor for fogging were calculated. RESULTS: Tear exchange occurred within 5 minutes in 64% of eyes. The difference in fluid reservoir optical density for eyes with and without tear exchange was greatest when tear exchange occurred within 10 seconds. Tear exchange between 1-5 minutes was not predictive for fogging. Tear exchange occurring within 10 seconds showed low sensitivity and NPV, but high specificity (87%) and PPV (71%) for predicting fogging. CONCLUSION: Tear exchange occurred in a majority of eyes in this study. Scleral lens wearers with a rapid tear exchange rate were more likely to report midday fogging.