A study recently published in Acta Ophthalmologica investigated the effect of seasonal variation on central serous chorioretinopathy (CSC) incidence.
Give me some background.
CSC is a chorioretinal disease characterized by serous subretinal fluid (SRF) the macula, resulting in sudden central vision loss.
Previous studies have suggested that broader environmental influences, including seasonal variation, may contribute to disease onset, with reports highlighting an increased incidence of CSC in spring compared to winter.
- This phenomenon is often referred to as the seasonality of a disease, which is defined as a cyclic change in either disease occurrence or severity over a year.
And why should we care about this?
As the study authors explained: Exploring the seasonality of CSC offers a natural experiment to examine how environmental exposures intersect with individual susceptibility across time and place.
Now talk about this study.
The research team performed a systematic search across the following databases in June 2025:
- PubMed
- Embase
- Cochrane Central
- Web of Science Core Collection
- Current Contents Connect
- Data Citation Index
- Derwent Innovations Index
- KCI-Korean Journal Database
- ProQuest Dissertations and Theses Citation Index
- SciELO Citation Index
Eligible studies included observational designs reporting CSC incidence or frequency across seasons, and case reports were excluded.
And in total: Five studies encompassing 907 participants met the inclusion criteria, with three having sufficient data for quantitative meta-analysis and the remaining two conference abstracts included in the qualitative analysis.
Findings?
Using summer as the reference season, the meta-analysis demonstrated a significantly increased incidence of CSC in spring (odds ratio [OR]: 1.42, 95% confidence interval [CI]: 1.18-1.73, p=0.0003) and autumn (OR: 1.23, 95% CI: 1.02-1.48, p=0.03).
- However: No significant difference was observed for winter (OR: 0.97, 95% CI: 0.80-1.19, p=0.80).
And take note: The remaining two studies that were not included in the meta-analysis also reported seasonal trends consistent with these findings.
Expert opinion?
The study authors outlined how the observed seasonal variation may be explained by a number of biologically plausible explanations:
- Seasonal shifts in photoperiod modify the circadian melatonin–cortisol axis and autonomic tone, affecting choroidal vascular regulation and permeability
- Case in point: One study hypothesized that the lower CSC incidence in summer may be associated with increased water evaporation from the body, which may influence choroidal homeostasis
- Psychosocial stress, which frequently varies throughout the year, enhances glucocorticoid and mineralocorticoid signaling (well known CSC triggers)
- Environmental factors, such as temperature, humidity, and seasons allergens may further contribute to choroidal congestion and leak
Any limitations to note?
A few, including:
- Variability of the study designs led to significant heterogeneity in data
- Two of the studies were over 20 years old
- Retrospective nature of most included studies
- Limited geographical representation that primarily focused on individuals from North America and East Asia
- Tropical and subtropical countries may not be able to use the concept of four distinct seasons, which typically only have wet and dry seasons
And lastly … the take home.
These findings demonstrate a notable seasonal variation in CSC incidence, with a consistently increased risk during spring and autumn compared with summer.
For the future: Further prospective studies across diverse regions with more consistent diagnostic criteria are warranted to elucidate how seasonal environmental and physiological mechanisms may contribute to CSC development.