Tear Break-Up Time and Seasonal Variation in Intraocular Pressure in a Japanese Population

Seasonal variations in anterior segment angle parameters in myopes and emmetropes

CLINICAL RELEVANCE

Seasonal variations are known to occur in a range of ocular parameters and in conditions including refractive error and glaucoma. It is of clinical importance to know if seasonal changes also occur in anterior segment angle parameters, given that they can influence these conditions.

BACKGROUND

The study aimed to examine the seasonal variations in anterior segment angle parameters in healthy young adults.

METHODS

Twenty-three emmetropic participants with a mean age of 26.17 ± 4.43 years and 22 myopic participants with a mean age of 27.27 ± 4.47 years completed four seasons of data collection. Anterior segment angle parameters were measured using swept-source anterior segment optical coherence tomography. Intraocular pressure (IOP) and objective refraction were also measured. Repeated-measures analysis of variance was used to determine the effect of season and refractive error on the various ocular parameters.

RESULTS

A significant main effect of season was found for the majority of anterior segment angle parameters, including the angle opening distance at 500 and 750 µm from the scleral spur (p = 0.02, p = 0.006, respectively), angle recess area at 500 and 750 µm from the scleral spur (both p = 0.002), and trabecular iris space area at 500 and 750 µm from the scleral (p = 0.02, p = 0.008, respectively). However, measures of anterior chamber depth and trabecular iris angle did not exhibit statistically significant seasonal variations (all p > 0.05). A significant main effect of season was also found for the changes in IOP (p = 0.004) and objective refraction (p < 0.001). There was no season by refractive group interaction for any anterior segment angle parameter or IOP (all p > 0.05).

CONCLUSION

There is a small but significant seasonal changes in the anterior segment angle parameters, refractive error, and IOP in healthy young adult males, in which the anterior segment angle dimensions are narrower, the IOP is higher, and the refraction is more myopic during winter.

Seasonal Variation and Trend of Intraocular Pressure Decrease Over a 20-Year Period in Normal-Tension Glaucoma Patients

PURPOSE

To investigate the trend of seasonal variation of intraocular pressure (IOP) in patients with normal-tension glaucoma over a 20-year period by retrospectively analyzing the Kyoto Prefectural University of Medicine Glaucoma Registry database as real-world data.

DESIGN

Retrospective cohort study.

METHODS

Data points (n = 49,007) were extracted retrospectively from the medical records of 1774 patients with normal-tension glaucoma (665 male patients and 1109 female patients; mean ± SD age was 59.8 ± 14.4 years; and mean ± SD observation period was 5.6 ± 4.4 years) seen over the 20-year period. We first calculated the mean IOP from all available data of each month from January 1997 through December 2016. The data were then categorized into 5 groups of 4 consecutive years each (1997-2000, 2001-2004, 2005-2008, 2009-2012, and 2013-2016) and the mean IOP of each month within the group was calculated. Seasonal variations of IOP over the 20-year study period and in the 5 consecutive groups were then investigated via nonlinear multiple regression analysis.

RESULTS

A continuous decrease of IOP was detected throughout the 20-year period (P < .001), with distinct seasonal variation. The annual mean ± SD IOP was highest (13.9 ± 2.7 mm Hg) in the oldest group (1997-2000), with a gradual decrease in each subsequent group, finally becoming lowest (12.3 ± 2.7 mm Hg) in the most recent group (2013-2016) (P < .001), and all of them were accompanied by distinct seasonal variation (P < .001).

CONCLUSIONS

Based on the Kyoto Prefectural University of Medicine Glaucoma Registry real-world longitudinal data, our findings revealed a continuous decrease and distinct seasonal variation of IOP in patients with normal-tension glaucoma throughout the 20-year study period.

Seasonal fluctuation in intraocular pressure and its associated factors in primary open-angle glaucoma

BACKGROUND/OBJECTIVES

To evaluate seasonal fluctuations in intraocular pressure (IOP) in primary open-angle glaucoma (POAG) and its associated factors.

SUBJECTS/METHODS

POAG patients treated only with glaucoma eye drops were enroled. Winter and summer IOPs were evaluated. The Seasonal fluctuation rate of IOP was defined as follows: (mean winter IOP-mean summer IOP)/mean IOP in all seasons. Multiple linear regression analysis was used to explore factors associated with the seasonal IOP fluctuation rate including: age, gender, family history of glaucoma, type of glaucoma, number of eye drops, type of eye drops, mean deviation (MD) value, MD slope, disc haemorrhage, central corneal thickness and spherical equivalent.

RESULTS

Winter IOP was higher than summer IOP in 204 POAG eyes of 204 patients, including 162 eyes with normal tension glaucoma (NTG) (13.2 ± 2.7 vs. 12.0 ± 2.3 mmHg, P < 0.001). The mean age and follow-up duration were 63.3 ± 11.4 years and 140.0 ± 66.9 months. Initial MD and MD slope were -2.1 ± 3.4 dB and -0.07 ± 0.50 dB/year, respectively. POAG was positively associated with the rate of seasonal IOP fluctuations compared to NTG (β = 5.29, P = 0.013). Family history, and timolol and carteolol use were also factors associated with the IOP fluctuation rate (β = -6.27, P = 0.007; β = 4.94, P = 0.030; and β = 4.51, P = 0.042, respectively).

CONCLUSIONS

We confirmed seasonal IOP fluctuations in POAG. Type of glaucoma, family history of glaucoma, and β-blocker use might influence IOP fluctuations.

Seasonal Fluctuation in Intraocular Pressure and Retinal Nerve Fiber Layer Thinning in Primary Open-Angle Glaucoma

PURPOSE

To detect seasonal fluctuations in intraocular pressure (IOP) in healthy eyes and eyes with primary open-angle glaucoma (POAG) and to evaluate whether these seasonal fluctuations affect retinal nerve fiber layer (RNFL) thinning in eyes with POAG.

DESIGN

Observational, retrospective cohort study.

PARTICIPANTS

Healthy population who underwent a comprehensive health check-up and patients with POAG using only topical medications were enrolled.

METHODS

Kaplan-Meier survival analysis was used to compare the cumulative incidence probabilities of RNFL thinning between different seasonal IOP fluctuation groups. A Cox proportional hazards model, with adjustments for potential confounding factors, was used to evaluate the association between seasonal fluctuations in IOP and RNFL thinning.

MAIN OUTCOME MEASURES

Intraocular pressure fluctuation rate calculated from winter and summer IOPs and RNFL thinning as determined by event-based analysis with high-definition OCT.

RESULTS

A total of 12 686 healthy eyes and 179 eyes of 179 POAG patients showed a significantly higher IOP in winter than in summer (healthy, 13.2 ± 3.0 mmHg vs. 12.5 ± 2.9 mmHg [P < 0.001]; POAG, 13.1 ± 2.7 mmHg vs. 11.8 ± 2.3 mmHg [P < 0.001]). In POAG patients, the mean age at initial OCT and follow-up duration were 55.1 ± 11.7 years and 98.4 ± 26.4 months, respectively. The mean deviation (MD) at first visit, MD slope, and RNFL thinning rate were -2.2 ± 3.4 dB, -0.07 ± 0.44 dB/year, and -0.44 ± 0.88 μm/year, respectively. During the study period, 85 eyes (47.5%) showed RNFL thinning progression. Kaplan-Meier analysis showed that a high seasonal IOP fluctuation rate significantly suppressed RNFL thinning (P < 0.05, log-rank test). After adjusting for confounders in the Cox analysis, the seasonal IOP fluctuation rate still showed a significantly negative association with RNFL thinning (hazard ratio, 0.98; 95% confidence interval, 0.96-0.99; P = 0.005).

CONCLUSIONS

Winter IOP was higher than summer IOP in both healthy and POAG eyes. The temporary IOP decline in summer, rather than a constant IOP throughout the year, may prevent glaucoma progression.