Fixation stability is the ability of the eyes to maintain a constant and stable gaze on the fixation target. One of the visual functions that can be affected by unstable fixation is stereopsis. Stereovision is important for a variety of daily tasks, as well as for using stereoscopic displays in visualizations and entertainment, such as watching movies and playing video games. The interaction between fixational stability and stereopsis in different conditions has often been studied in children with amblyopia. The aim of our research is to explore the relationships between binocular fixation stability and stereopsis in school-aged children who do not have amblyopia and strabismus in their anamnesis. The children were divided into two groups: those with normal stereoacuity (≤ 60 arcsec in the TNO test) and those with reduced stereoacuity (≥120 arcsec in the TNO test). The fixation target was demonstrated on a computer screen, and eye movements during fixation were recorded using a Tobii Pro Fusion eye tracker operating at 250 Hz. The results demonstrate that children with better stereoacuity tend to have more stable fixation compared to children with reduced stereoacuity. However, the difference in fixation stability was not significant.
Purpose: Keratoconus is an eye disorder that results in progressive thinning of the cornea. Corneal biomechanical data can be used for early diagnosis of keratoconus disease. Measurements show the first signs of corneal pathological changes while anterior surface topographic maps don’t. In cases of severe keratoconus, the measurements of corneal biomechanical parameters can be modified due to eye lid tension that can influence the evaluation of the keratoconus progression. Aim of this study was to determine differences in corneal biomechanical parameters in keratoconus patients depending on the stage of keratoconus. Method: In our research participated 144 keratoconus patients (256 eyes) and 61 control group patients (122 eyes). We evaluated the corneal thickness (Oculus Pentacam) and corneal biomechanical response with Oculus Corvis. We analyzed the Corvis biomechanical index (CBI), tomographic biomechanical index (TBI), and corneal elevation deviation index (BAD D). The results were compared between the control group and the different stages of the keratoconus patients and were analyzed with ANOVA (two factor) and linear regression. Results: As the keratoconus progresses, corneal thickness decreases (r=-0,98), corneal elasticity decreases (r=0,94), elevation height increases (r=0,77) and the deviation of the corneal elevation from the normative values increases (r=0,98). Conclusion: The results show a strong negative correlation between the stage of keratoconus and the decrease in corneal thickness. Corneal thickness, compared with the control group, decreases statistically significantly (p <0,05), starting with keratoconus stage 2, but CBI, TBI and BAD D corneal biomechanical index values - starting with keratoconus 0-1 stage.
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