Relationship between Diurnal Variation in Intraocular Pressure and Central Corneal Power

PAX6 gene promoter methylation is correlated with myopia in Chinese adolescents: a pilot sutdy

PURPOSE

A large number of epidemiological studies have shown that myopia is a complex disease involving genetic, environmental, and behavioral factors. The purpose of this study was to explore the role of PAX6 gene methylation in myopia in Chinese adolescents.

METHODS

Eighty junior high school students were divided into four groups based on their vision test results: mild myopia, moderate myopia, severe myopia, and non-myopia control. The methylation level of PAX6 gene promoter was detected by bisulfate pyrosequencing.

RESULTS

The methylation level of PAX6 gene in myopia group (8.06% ± 1.43%) was slightly but significantly higher than that in non-myopia controls (7.26% ± 1.17%). In addition, PAX6 gene methylation levels presented a decreasing pattern along with the aggravation of myopia. Post-hoc analysis indicated significant inter-group differences for the mild myopia group and other groups (All p < .05). In the subgroup analysis by gender, the methylation level of PAX6 gene promoter in girls was higher than that in boys (p = .023). The ROC curves showed a high accuracy of PAX6 gene methylation to predict mild myopia (AUC (95% CI) = 0.828 (0.709-0.947), p < .001).

CONCLUSIONS

The methylation of PAX6 gene might play a role in the onset and progression of myopia in Chinese adolescents. And this could potentially explore the potential molecular mechanisms of juvenile myopia in the future.

Design and development of a noninvasive ocular pressure estimator

SIGNIFICANCE

A snapshot intraocular pressure (IOP) is ineffective in identifying the IOP peak and fluctuation, especially during sleep. Because IOP variability plays a significant role in the progression of glaucoma, monitoring the IOP, especially during sleep, is essential to capture the dynamic nature of IOP.

PURPOSE

We aimed to design an ocular pressure estimator (OPE) that can reliably and accurately measure the IOP noninvasively over closed-eyelid condition.

METHODS

Ocular pressure estimator works on the principle that the external pressure applied by raising the IOP of the eyeball is transmitted through a compressible septum to the pressure sensor, thus recording the IOP. A fluid-filled pouch with a pressure sensor was placed over a rubber glove mimicking the eyelid (septum), covering the cornea of enucleated goat eyeballs. A pressure-controlled setup was connected to a goat cadaver eye, which was validated by a rebound tonometer. Cannulation of eyeballs through the lower limbus had the least difference from the control setup values documented using rebound tonometer, compared with cannulation through the optic nerve. Intraocular pressures ranging from 3 to 30 mmHg was induced, and the outputs recorded using OPE were amplified and recorded for 10 minutes (n = 10 eyes). We stratified the randomization of the number of times and the induced pressures.

RESULTS

The measurements recorded were found to be linear when measured against an IOP range of 3 to 30 mmHg. The device has excellent reliability (intraclass correlation coefficient, 0.998). The repeatability coefficient and coefficient of variations were 4.24 (3.60 to 4.87) and 8.61% (7.33 to 9.90), respectively. The overall mean difference ± SD between induced IOP and the OPE was 0.22 ± 3.50 (95% confidence interval, -0.35 to 0.79) mmHg across all IOP ranges.

CONCLUSIONS

Ocular pressure estimator offers a promising approach for reliably and accurately measuring IOP and its fluctuation noninvasively under a condition mimicking a closed eye.

Assessing Agreement and Variability Among Alternative Devices for Intraocular Pressure Measurement: A Comparative Study

Purpose

Intraocular pressure (IOP) measurement is critical in diagnosing and managing eye conditions. This study aims to assess the comparability of three alternative devices for measuring IOP: Noncontact tonometer, Icare rebound tonometer, and Tono-Pen.

Patients and Methods

A cross-sectional study included 172 adult participants (87 males and 85 females) who underwent IOP and central corneal thickness (CCT) assessments. IOP was measured using Noncontact (Canon TX-20), Icare (Icare TA01i), and Tono-Pen (Tonopen XL). CCT was measured with the built-in pachymetry of the Noncontact tonometer. Correlation coefficients and Bland-Altman analyses were conducted to assess the relationships and agreements between these tonometers. Participants were grouped based on IOP and CCT levels. The mean of the standard deviation of the three tonometer results was calculated to evaluate measurement result variability. One-way analysis of variance was conducted for comparing between the groups.

Results

IOP measurements among the three devices were not significantly different, indicating their comparability. Correlation analysis revealed strong correlations between the tonometers. Bland-Altman analysis showed good agreement, with the Icare rebound tonometer and Tono-Pen exhibiting narrower limits of agreement. Furthermore, IOP levels influenced measurement result variability, with higher IOP levels associated with greater variance.

Conclusion

This study demonstrates that the alternative devices examined can provide reliable IOP measurements. It highlights the potential of these alternative devices for IOP measurement. These findings have implications for clinical practice, offering practitioners additional tools for accurate IOP assessment.

Intraocular Pressure Fluctuation Throughout the Day

Purpose To compare intraocular pressure (IOP) values at different time points, both in the total sample and according to iridocorneal angle aperture, to assess whether IOP fluctuations were constant throughout the day, and to examine correlations with other factors. Methods Over a single day, the IOP of 34 volunteers was measured at three-hour intervals from 9:00 a.m. to 6:00 p.m. To avoid any IOP value being affected by other measurements, anamnesis, slit-lamp evaluation (with iridocorneal angle measurement), and refractive status were performed after the final measurement. The differences between IOP values at different time points and IOP fluctuation at three-hour intervals were compared by ANOVA and Friedman test, respectively, both for the total group and according to iridocorneal angle aperture. For relationships, Pearson's correlation was performed for parametric variables and Spearman's correlation for nonparametric variables. Results Significant differences were observed in IOP between time points for the total sample (p < 0.001), but not for a narrow-angle group (p = 0.058). No significant differences were found in IOP fluctuations at three-hour intervals either in the total sample or according to angle aperture (all p ≥ 0.332). There was a positive correlation of IOP at different time points (all r ≥ 0.646, all p < 0.001) but no relationship with spherical equivalent, age, or sleep duration (all p ≥ 0.057). IOP at 12:00 p.m. was correlated with a 12:00 p.m. to 3:00 p.m. fluctuation (r = 0.428, p = 0.012); and IOP fluctuation between 9:00 a.m. and 12:00 p.m. was correlated with age (r = 0.485, p = 0.004). Conclusion As IOP decreases from morning until at least 6:00 p.m., measuring these two values during clinical evaluation is essential for the effective monitoring and prevention of IOP-related diseases.