Seasonal and Temporal Trends of Infectious Keratitis in Northern Vietnam.

The epidemiology of corneal ulcers in Vietnam has not been well characterized. In this report, we reviewed retrospectively the microbiological data of patients with a clinical diagnosis of corneal ulcer at the microbiology laboratory of Vietnam National Eye Hospital from January 1, 2010 to March 31, 2023. We observed a seasonal pattern for fungal and microsporidial keratitis, with an annual peak in November, and an inverse relationship between fungal keratitis and inclement weather. The November peak coincided with one of the major harvesting seasons in Vietnam. We also observed increasing numbers of microsporidial and Acanthamoeba keratitis cases in recent years. Knowledge of these trends are helpful in guiding empirical treatment of corneal infections and preventing corneal blindness.

Circadian clock regulates tear secretion in the lacrimal gland.

Although diurnal variations have been observed in tear film parameters in various species, the molecular mechanisms that control circadian tear secretion remain unclear. The aim of our study was to evaluate the role of clock genes in the lacrimal gland (LG) in regulation of tear secretion. Tear volume was measured by cotton thread test in core clock genes deficient (Cry1-/-Cry2-/--) mice which are behaviorally arrhythmic. Real-time quantitative RT-PCR was used to examine expression profiles of core clock genes in the LG including Per1, Per2, Per3, Clock, Bmal1. All experiments were performed under a 12 h of light and 12 h of darkness (LD) and constant dark (DD) conditions. Under both LD and DD conditions, diurnal and circadian rhythms were observed in tear secretion of wild-type mice with tear volume increased in the objective and subjective night while disruption in diurnal and circadian variations of tear secretion were found in Cry1-/-Cry2-/--mice. In wild-type mice, the expression level of major clock genes in the LG showed oscillatory patterns under both LD and DD conditions. In contrast, expression clock genes in the lacrimal gland of Cry1-/-Cry2-/-- mice showed complete loss of oscillation regardless of environmental light conditions. These findings confirmed the presence of diurnal and circadian rhythms of tear secretion and provided evidences supporting a critical role for the clock in the control of tear secretion.

Influence of Meibomian Gland Dysfunction and Friction-Related Disease on the Severity of Dry Eye.

PURPOSE: To evaluate the effect of meibomian gland dysfunction (MGD) and friction-related disease (FRD) on the severity of dry eye disease (DED). DESIGN: Cross-sectional observational study. PARTICIPANTS: This study enrolled 449 patients with DED (63 men and 386 women; mean age, 62.6±15.7 years [range, 21-90 years]) for analysis. METHODS: Subjective symptoms, the ocular surface, tear function, and the presence of MGD and FRD (superior limbic keratoconjunctivitis, conjunctivochalasis, and lid wiper epitheliopathy) were investigated. MAIN OUTCOME MEASURES: Schirmer value, tear film breakup time (TBUT), and keratoconjunctival score. RESULTS: We classified the participants into aqueous-deficient dry eye (ADDE; n = 231 [51.4%]) and short TBUT dry eye subtype (TBUT-DE; n = 109 [24.3%]) subgroups. The TBUT was shorter in patients with MGD than in those without MGD, whereas other ocular signs showed no difference (TBUT: MGD present, 1.97±1.02 seconds; MGD absent, 2.94±1.63 seconds [P < 0.001]; ADDE/MGD present, 1.94±1.08 seconds; ADDE/MGD absent, 2.77±1.61 seconds [P < 0.001]; short TBUT-DE/MGD present, 2.07±0.97 seconds; short TBUT-DE/MGD absent, 2.94±1.23 seconds [P = 0.01]). The ADDE patients with FRD showed a worse TBUT than ADDE patients without FRD (TBUT: ADDE/FRD present, 2.08±1.39 seconds; ADDE/FRD absent, 2.92±1.54 seconds; P < 0.001). CONCLUSIONS: This study showed associations between MGD, FRD, or both and ocular signs in DED. In the presence of MGD, FRD, or both, TBUT was significantly shortened regardless of the dry eye status or subtype.