Keratometry Changes Between Year One to Seven After Corneal Cross-Linking in Patients With Keratoconus.

PURPOSE: We evaluated the timing at and extent to which midterm to long-term keratometric changes can occur in year 1 to 7 after corneal collagen cross-linking (CXL) in patients with keratoconus. METHODS: We conducted a subgroup analysis of a retrospective cohort study of all consecutive patients who underwent CXL at our cornea center between 2007 and 2011. The inclusion criteria comprised CXL according to the Dresden protocol and a full set of keratometry parameters collected by Scheimpflug tomography preoperatively and at year 1, 3, 5, and 7 after CXL. In addition, best-corrected visual acuity was evaluated. RESULTS: Sixty-three eyes of 47 patients were enrolled. Mean age was 25.46 years ±7.39 years (80.9% male patients). All relevant keratometric parameters showed significant improvement at year 1 after CXL (except for posterior astigmatism). According to mixed-effects model analysis, they all showed further significant change at different points in time between year 1, 3, 5, and 7 (except for K1). In addition, best-corrected visual acuity improved statistically significant between year 1, 3, 5, and 7. Suspected disease progression was noted in 22.2% of patients, mostly between year 1 and 3 after CXL. CONCLUSIONS: After initial improvement 1 year after CXL, keratometric and functional parameters were stable until year 5 after CXL in most cases; further improvement can take place even after up to 7 years post-CXL. By contrast, in case of disease progression, changes seem to occur already between year 1 and 3 after CXL.

Corneal cross-linking in patients with keratoconus: up to 13 years of follow-up.

INTRODUCTION: To evaluate long-term safety and efficacy of corneal collagen cross-linking (CXL) in patients with keratoconus up to 13 years. MATERIALS AND METHODS: In this mono-centre exploratory study, we included all consecutive patients who underwent CXL in our cornea centre from 01/01/2007 to 12/30/2011 and met the inclusion criteria. CXL was performed in all patients according to the Dresden protocol. Evaluation included best-corrected visual acuity (BCVA), topographic keratometry by Scheimpflug corneal tomography and endothelial cell count (ECC). Follow-up measurements were taken up to 13 years after treatment were compared with baseline values. RESULTS: The study enrolled 168 eyes. The mean age of our patients was 26.3 years ± 7.8 years. A complete topographic dataset was available 1 year postoperatively for 142 eyes, 5 years postoperatively for 105 eyes, 10 years postoperatively for 61 eyes and 13 years postoperatively for 9 eyes. BCVA increased statistically significant after 1 year, 5 years and 10 years and non-significantly after 13 years. All keratometric parameters with exception of posterior astigmatism showed a statistically significant decrease after 1 year, 5 years and 10 years. After 13 years, the decrease was statistically significant only in Kmax, K2 and thinnest cornea. No significant changes in ECC were detected. Three eyes received Re-CXL, none of the eyes received penetrating keratoplasty and no infections occurred in this cohort. CONCLUSIONS: CXL can slow down or even stop the progression of keratoconus in the majority of cases. The effect is long-lasting with excellent safety.

The impact of the verbal instruction and task characteristics on effect-based action control.

According to ideomotor theory, when people perform a movement and observe its subsequent effect, they acquire a bidirectional action-effect association. If at a later point they want to produce the effect, its anticipation activates and allows executing the corresponding action. In ideomotor induction tasks, several task characteristics determine whether participants use the experimentally induced action-effect associations to pre-activate the corresponding actions. Here, we assess the impact of the verbal instruction, the task relevance of the effect stimuli and the presentation of post-response effects on the expression of action-effect associations. The results show that an instruction stressing the stimulus-effect correspondence prompts participants to utilize the presented effects more than an instruction stressing the stimulus-response correspondence. Furthermore, the induced action-effect associations were only expressed when the effects were relevant for the task and when post-response effects were presented in the test phase. These findings show the importance of the particular task construction for the expression of the experimentally manipulated action-effect knowledge.

Dissociating decision strategies in free-choice tasks - A mouse tracking analysis.

Everyday life offers a variety of possible actions, from which we choose one that corresponds to our intended goals. How do these goals and actions interact within the mind? One way to investigate this question is free-choice tasks, where participants freely choose the action they want to perform on any given trial. Such tasks are used in research on voluntary actions and goal-driven behavior, such as ideomotor theory. However, these tasks leave participants with a substantial amount of freedom and allow for different response strategies. Such strategies can, though being hidden in the final data, influence the results, for example by hiding the effects of manipulations of interest. To better understand participants' behavior in free-choice tasks, we used mouse tracking in an ideomotor free-choice experiment, where participants learn the connection between an action and an effect. Subsequently, they have to freely choose between actions, while the former effect is presented as a stimulus. We identified two distinct groups that applied different decision strategies. The first group made the decision at the beginning of or before the trial, irrespective of the yet to be presented effect stimulus. The second group decided within the trial and was affected by the stimulus more often. This suggests that people handle free-choice tasks differently which is expressed in heterogeneous choice patterns and response times and an underestimation of the examined effects. These differences potentially limit the reliability of inferences from free-choice experiments and should be considered in the interpretation of their results.

Ethene stabilization on Cu(111) by surface roughness.

The molecular vibrations of ethene adsorbed on roughened Cu(111) surfaces have been investigated with high resolution electron energy loss spectroscopy and density-functional-theory calculations. The roughness was introduced by sputtering or evaporation of copper, respectively, on the cooled surface. We found stabilization of the ethene layer compared to ethene adsorbed on pristine Cu(111). Furthermore, two new vibrational features observed on the rough surface can be assigned to frustrated translations and rotations of the ethene molecule on surface defects and are indicative of a different binding on the rough surface.