CCHF is a fatal viral disease that can progress with multisystem involvement in the viral hemorrhagic fever (VHA) group. When the literature was reviewed, it was observed that ocular findings such as vitreous hemorrhage, optic neuritis, uveitis, macular edema, maculopathy, and vascular occlusions were reported in Dengue Fever and Rift Valley Fever in the VHA group [9, 10]. In CCHF cases, photophobia, conjunctival and retinal hemorrhages, and conjunctival chemosis have been reported in ophthalmologic examinations [11–13].
The mechanism in CCHF pathogenesis is not fully understood. Influencing endothelial cells directly via viral vectors or indirectly via virus-mediated host-derived soluble factors plays important role [7]. An abnormal immune response occurs with endothelial dysfunction. It was determined that the levels of interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor (TNF-α) increased in the resulting cytokine storm [14]. In addition, endothelial damage can lead to increased vascular permeability, hemorrhage and coagulation disorders.
Engin et al [11] described conjunctival hemorrhage or point-like petechial type retinal hemorrhage in 73.7% of CCHF patients. It was stated that the findings regressed in the follow-ups and none of the patients had vision loss. No correlation was found between eye involvement and the severity of the disease and laboratory findings.
Yalınbaş et al [15] examined the ocular findings of 34 pediatric patients diagnosed with CCHF. They did not detect subconjunctival hemorrhage or retinal hemorrhage in any of the patients. They found conjunctival hyperemia in 50% of the patients and described increase in retinal vessel tortuosity and increase in vein dilatation in detailed fundus examination. The increase in retinal tortitosite has been linked to inflammation in systemic small vessels. In another study, Purtscher-like Retinopathy was defined in a case with Crimean-Congo Hemorrhagic Fever [16]. However, we didn’t detect subconjunctival or retinal hemorrhage in the detailed eye examination performed in our study. However, there is no previous study on whether CCHF has an effect on the choroid tissue.
The choroid is the structure that consists of rich vascular structures that feed the outer retina and retinal pigment epithelium, and ensures the preservation of healthy visual function [17]. Studies have shown that the stromal and vascular structure of the choroid is affected by a wide variety of systemic diseases. On the other hand, the health status of the choroid can give us clues about the systemic health status. [3]. Many studies have been published on the increase in choroidal thickness in patients with increased systemic inflammation such as Behçet’s disease, psoriasis and Covid 19 [18–20]. A decrease in choroidal thickness was observed in these diseases when followed up with anti-inflammatory therapy [20, 21].
CVI is a new parameter used for the evaluation of choroidal structure and vascularity using the binarization technique. CVI offers a more reliable, reproducible assessment and is calculated by dividing the luminal area by the total choroidal area [8].
LA and SA can be affected by some systemic and local factors. In recent studies, it has been argued that the increase in LA may be the result of dilatation, leakage and enlargement of the extravascular space in the choroidal vessels [22, 23]. Autoinflammatory processes leading to stromal edema have been blamed for the increase in SA caused by connective tissue elements such as mast cells, melanocytes and fibroblasts [24, 25]. In our study, we thought that the increase in choroidal thickness, LA, SA and TCA might be related to the intense inflammatory process in CCHF and increased capillary permeability. However, since the increase was proportional in both areas, CVI may not have been affected.
Both LA and SA increased in CCHF group compared to controls in our study. However, there was no difference CVI in both groups. We think that vasculary permeability increased in CCHF cases due to the inflammation and this resulted an increase in both LA and SA. This increase was smilar in LA and SA. Therefore, CVI was not change in CCHF when compared to control group. Consequently, this results suggest that choroid can be affected in CCHF cases due to the inflammatory process of the disease.
In a recent study, the choroidal parameters of the inflammatory disease SLE and the control group were compared. It was reported that ChT, TCA, SA and LA values were higher in the SLE group, but there was no difference in CVI values [26]. We also obtained similar results in our study.
In conclusion, patients with CCHF had a significantly thicker choroid compared to healthy subjects, suggesting that inflammation associated with CCHF may affect the choroid. Choroidal parameters such as CT, LA, SA and TCA may be used for monitoring of CCHF. There are not enough studies in the literature evaluating the effects of CCHF on ocular structures. This study results may contribute to useful information to understand of the pathogenesis of CCHF