In vivo human corneal hydration control dynamics: A new model

PURPOSE. To introduce a new model describing human in vivo corneal deswelling after hypoxic contact lens wear, based on a damped harmonic oscillator, which can describe an overshoot in corneal deswelling, to compare this new model with the currently used exponential model, and also to test whether a diurnal variation in baseline corneal thickness exists that would have to be taken into consideration when calculating corneal deswelling curves. METHODS. In nine healthy young adults, corneal thickness was measured every 30 minutes for 11.5 hours on average using modified optical pachometry (natural test). On another day, corneal deswelling was monitored for 11.1 hours on average after 2 hours of hypoxic contact lens wear (stress test). The damped harmonic oscillator model and the exponential model were used to calculate best-fitting deswelling curves. Natural test data were analyzed for the presence of a trend. Goodness of fit of the curves to the experimental data was analyzed using the F test. RESULTS. In 82% of the deswelling curves the new damped harmonic oscillator model provided a better fit to the data than the exponential model (P < 0.05). An average overshoot in corneal thickness recovery of 5 μm (range, 0-11 μm) was found. In 50% of the natural tests significant trends were found, without any consistent similarities. The overshoot could not be explained by these trends. CONCLUSIONS. The new damped harmonic oscillator model describes corneal deswelling after hypoxic contact lens wear more accurately than the exponential model. No consistent diurnal variation could be demonstrated

In vivo human corneal hydration control dynamics: A new model

PURPOSE. To introduce a new model describing human in vivo corneal deswelling after hypoxic contact lens wear, based on a damped harmonic oscillator, which can describe an overshoot in corneal deswelling, to compare this new model with the currently used exponential model, and also to test whether a diurnal variation in baseline corneal thickness exists that would have to be taken into consideration when calculating corneal deswelling curves. METHODS. In nine healthy young adults, corneal thickness was measured every 30 minutes for 11.5 hours on average using modified optical pachometry (natural test). On another day, corneal deswelling was monitored for 11.1 hours on average after 2 hours of hypoxic contact lens wear (stress test). The damped harmonic oscillator model and the exponential model were used to calculate best-fitting deswelling curves. Natural test data were analyzed for the presence of a trend. Goodness of fit of the curves to the experimental data was analyzed using the F test. RESULTS. In 82% of the deswelling curves the new damped harmonic oscillator model provided a better fit to the data than the exponential model (P < 0.05). An average overshoot in corneal thickness recovery of 5 μm (range, 0-11 μm) was found. In 50% of the natural tests significant trends were found, without any consistent similarities. The overshoot could not be explained by these trends. CONCLUSIONS. The new damped harmonic oscillator model describes corneal deswelling after hypoxic contact lens wear more accurately than the exponential model. No consistent diurnal variation could be demonstrated

Quality of vision in patients with fuchs endothelial dystrophy and after descemet stripping endothelialkeratoplasty.

To evaluate the quality of vision (visual acuity and straylight) in patients with Fuchs dystrophy and the improvement in visual quality after Descemet stripping endothelial keratoplasty (DSEK). There was an observational case series (Amsterdam group) and a prospective interventional case series (Mayo group). Corrected distance visual acuity (CDVA), straylight, and corneal thickness were measured in patients with phakic and pseudophakic eyes with Fuchs dystrophy recruited at the Academic Medical Center, Amsterdam, the Netherlands (99 eyes), and at Mayo Clinic, Rochester, Minnesota (48 eyes). The Mayo group was also examined at 1, 3, 6, and 12 months after DSEK; all these eyes were rendered pseudophakic during DSEK. Eyes with Fuchs dystrophy had decreased CDVA (mean [SD], 0.42 [0.26] logMAR; Snellen equivalent 20/53) and increased straylight (mean [SD], 1.54 [0.24] logarithm of the straylight parameter) compared with normal eyes. Younger patients were affected more by increased straylight than by decreased CDVA. Corrected distance visual acuity (r = 0.26; P = .003; n = 135) and straylight (r = 0.26; P = .003; n = 133) were correlated with corneal thickness. Corrected distance visual acuity and straylight improved at all postoperative examinations (P < .001), and improvement in straylight from before DSEK to 12 months after DSEK correlated with recipient age (r = -0.43; P = .01; n = 33). Improvement in straylight was more predictable than that of CDVA and was associated with preoperative straylight more than 1.33 logarithm of the straylight parameter. Quality of vision is severely impaired in patients with Fuchs dystrophy and improves significantly after DSEK. Straylight improves more in younger than in older eyes after DSEK. Preoperative straylight can be a useful clinical metric to predict postoperative improvement, especially in cases where preoperative visual acuity is close to 20/2