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Marianne Fritz, Viviane Grewing, Daniel Boehringer, Philip Maier, Thabo Lapp, Thomas Reinhard, Katrin Wacker; Diurnal corneal thickness variation in Fuchs Endothelial Corneal Dystrophy. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3874.
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© ARVO (1962-2015); The Authors (2016-present)
Diagnostic uncertainty in Fuchs endothelial corneal dystrophy eyes makes precise treatment selection difficult. To date, the amount of diurnal variation of corneal edema is unknown. In this study, we quantified the amount of corneal edema variation in Fuchs dystrophy and healthy corneas over the course of the day.
In this prospective study, we assessed central corneal thickness (primary outcome) and posterior corneal surface eccentricity (Q value) as parameters of edema in advanced Fuchs dystrophy eyes undergoing endothelial keratoplasty and in normal corneas using Scheimpflug imaging. All participants were measured at three timepoints: (1) around noon the day before surgery, (2) late afternoon the day before surgery, in presumed steady state, and (3) immediately upon awakening in hospital the morning of surgery after controlled overnight patching to ensure standardized eyelid closure. We used mixed-effect linear spline models to assess longitudinal changes and calculated 95% prediction intervals based on within-subject variance.
In this study, 37 Fuchs dystrophy and 10 control patients were included (median age, 70 years, IQR 64 to 77; 49% females). Directly upon awakening, mean corneal thickness was 662 µm (IQR, 624 to 704) in Fuchs dystrophy and 569 µm (IQR, 528 to 601) in control corneas. There were no systematic changes in corneal thickness in controls. In Fuchs dystrophy eyes, corneal thickness decreased by -11 µm per hour for the first four hours after awakening (95% CI, -13 to -9). During the same time, posterior Q decreased by -0.04 per hour (95% CI, -0.06 to -0.02) indicating that edema resolution steepened the central posterior cornea. Based on these data, 95% of advanced Fuchs dystrophy patients can be expected to have a change in corneal thickness over the first four hours after awakening between -53 µm to -32 µm (95% prediction interval). Beyond four hours after awakening, corneal thickness no longer changed considerably in Fuchs dystrophy (mean change per hour, 1 µm; 95% CI, -1 to 2).
Impaired hydration control in clinically advanced Fuchs patients is reflected by higher decrease in corneal thickness over the first four hours after awakening compared to controls. Beyond the first few hours after awakening, corneal thickness measurements in Fuchs dystrophy eyes are unlikely to vary more than in normal eyes.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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