Jan H. C. Kok

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In this study we investigated the properties of corneal aldehyde dehydrogenase (ALDH) in keratoconus corneas using various electrophoretic techniques combined with immunochemical and zymographic identification. Normal corneas and other pathologic corneal buttons obtained during keratoplastic surgery were used as a control. A significant (p < 0.001) lower(More)
Intolerance to rigid contact lenses in keratoconus may occur as a result of epithelial pathology or a suboptimal fitting. The application of a soft lens as a bandage makes it possible to tolerate a rigid lens over it. This study gives the results of 40 eyes in 26 patients who were consecutively fitted with a new aspheric combination lens. Thirty-five eyes(More)
In the past, keratoconus patients have been custom fit with multi-curve spherical contact lenses. Recently it has become possible to commercially manufacture aspherical contact lenses of high-Dk material. A computer assisted fitting technique may be used with these new lenses. We report 90 consecutive keratoconus eyes that were fit with aspherical high-Dk(More)
The influence of the permanent wear of rigid high Dk-lenses (nominal Dk 71 or 92) with elliptical geometry on the corneal endothelium was assessed. For this purpose the endothelium of 16 patients was compared by specular microscopy before and after the permanent wear. The wearing time of the lenses varied between 7 and 24 months. Computerized morphometric(More)
Extreme corneal surface disorders and dry-eye conditions cannot be adequately treated with corneal contact lenses. For these cases a scleral lens with a diameter of between 21 and 25 mm could be prescribed. In this study, high oxygen-permeable scleral contact lenses were fitted onto 50 eyes, of which 32 had a deviant corneal topography and 18 had dry-eye(More)
To examine the effect of rigid contact lens design on tear turnover the left and right eyes of 25 healthy volunteers were randomly fitted with either a spherical or an aspherical contact lens. Tear turnover is defined as the percentage of decrease of fluorescein concentration in the tear film per minute as a result of tear flow after instillation of(More)
Since antiquity many attempts were made and hence many methods were devised to minimize the disfiguration and stigmatization caused by leucoma corneae. Dermatography, a refined, modified tattooing technique, was used successfully in three cases of leucoma corneae. The materials and method are safe and simple. Over a 3-year follow-up period, no negative(More)
PURPOSE To examine whether corneal hydration control is impaired in corneas with endothelial morphologic changes (increased variation in cell size and cell angularity) due to long-term low gas-permeable contact lens wear. METHODS Twenty-one long-term wearers of low gas-permeable contact lenses (mean age, 41 years +/- 8 SD) and 18 age-matched controls(More)
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(More)
Ninety-nine eyes with keratoconus of 64 patients were examined using the sagittal radii method to determine the corneal flattening and compared with 100 eyes of 50 healthy controls. To express the degree of this flattening, four numerical eccentricity (E) values for each eye were calculated. The highest E value of the four was chosen as a parameter for(More)