PURPOSE: To develop a Scheimpflug-based image analysis technique to quantify tear exchange during scleral lens wear and investigate fluid reservoir tear dynamics during fenestrated lens wear. METHODS: Nine healthy participants wore a scleral lens (KATT™, Capricornia Contact Lenses) with a single 0.3 mm diameter limbal fenestration in one eye for 90 min. Central (0-2.5 mm from the corneal apex) and peripheral (-1.0 to 0 mm from the scleral spur) stromal cornea oedema was measured using optical coherence tomography. Scheimpflug images were obtained during lens wear at multiple time points following the application of sodium fluorescein to the bulbar conjunctiva. These images were exported and annotated manually to select the region of interest (the fluid reservoir) from which the intensity of each pixel was extracted to provide a measure of fluorescent intensity (in arbitrary units AU on a scale of 0-255) throughout lens wear across the central 10 mm. RESULTS: The coefficient of repeatability for central fluid reservoir intensity measurements was 7 AU (on a scale of 0-255 AU). Fluid reservoir fluorescent intensity varied with measurement location (p < 0.001), being greater towards the periphery (4 and 5 mm from the centre). On average, intensity differences between the peripheral and central fluid reservoir diminished within 10 min of sodium fluorescein application. Two patterns of tear dynamics were observed and were classified as low and high flow. Low flow participants (n = 6) exhibited greater central (3.72× more) and peripheral (2.25× more) corneal oedema, but the difference was not statistically significant. CONCLUSIONS: The ingress and mixing of sodium fluorescein within the fluid reservoir stabilised between central and peripheral locations after 10 min of fenestrated scleral lens wear. Two patterns of tear dynamics were observed (low and high flow), with low flow participants exhibiting greater corneal oedema. Future research utilising the developed technique may provide further insights into tear exchange during scleral lens wear with different fenestration sizes and configurations.
Fisher et al. (Wed,) studied this question.