Ocular manifestations of dengue fever in Bangladesh during its out break

Dengue fever, borne by Aedes aegypti mosquito, is one of the most common and most prevalent forms of flavivirus infections in humans, endemic in tropics and warm temperate regions of the world. We report a spectrum of ocular manifestations of dengue fever along with its associated laboratory findings. To study the ocular manifestations associated with dengue fever. This study was conducted in 600 patients hospitalized with diagnosis of dengue fever over a period of 3 months from March 2019 to May 2019. All patients underwent complete evaluation with respect to systemic and ophthalmic examination in different institutions of Bangladesh. A total of 600 patients were diagnosed with dengue fever; of which, 375 (62.5%) were men and 225 (37.5%) were women. Mean age was 32 years (20–60 years). Only 195 patients (32.7%) had complaints of retrobulbar pain in the eyes. 10 patients (1.67%) had blurring of vision. Ocular findings were present in 340 patients (56.7%). Most common anterior segment findings were subconjunctival haemorrhage in 275 patients (45.8%). Posterior segment findings were present in 80 patients (13.3%); of which, 70 (87.5%) had retinal haemorrhages. Ocular changes had resolved in all the cases, which came for follow-up in 8–10 weeks. It was mostly attributed to the improving platelet count.

Dengue fever, borne by Aedes aegypti mosquito, is one of the most common and most prevalent forms of flavivirus infections in humans, endemic in tropics and warm temperate regions of the world. We report a spectrum of ocular manifestations of dengue fever along with its associated laboratory findings. To study the ocular manifestations associated with dengue fever. This study was conducted in 600 patients hospitalized with diagnosis of dengue fever over a period of 3 months from March 2019 to May 2019. All patients underwent complete evaluation with respect to systemic and ophthalmic examination in different institutions of Bangladesh. A total of 600 patients were diagnosed with dengue fever; of which, 375 (62.5%) were men and 225 (37.5%) were women. Mean age was 32 years (20-60 years). Only 195 patients (32.7%) had complaints of retrobulbar pain in the eyes. 10 patients (1.67%) had blurring of vision. Ocular findings were present in 340 patients (56.7%). Most common anterior segment findings were subconjunctival haemorrhage in 275 patients (45.8%). Posterior segment findings were present in 80 patients (13.3%); of which, 70 (87.5%) had retinal haemorrhages. Ocular changes had resolved in all the cases, which came for follow-up in 8-10 weeks. It was mostly attributed to the improving platelet count. The incidence of ocular complications in dengue fever is increasing, hence all patients with dengue should be referred to an ophthalmologist to prevent any sight-threatening residual visual impairment secondary to maculopathy and optic neuropathy. [5][6][7][8] The main objective of this study was to evaluate the ophthalmic manifestations associated with dengue fever. Sheikh Mujib Medical University. The diagnosis was based on the presence of fever with other characteristic symptoms and signs. It was confirmed with serological testing with IgM and IgG antibody assay and decreasing platelet counts. The study was carried out for a period of 3 months from March 2019 to May 2019. All patients were asked detailed history with importance to visual symptoms. Detailed systemic examination and laboratory findings were recorded. All patients' best-corrected visual acuities were measured with Snellen acuity chart for both distance and near. Further, they were evaluated in detail with slit lamp examination using +90 D and +78 D lens. Dilated fundus examination was carried out with indirect ophthalmoscope using +20 D lens and fundus photos were taken with fundus camera. The patients with positive ophthalmic findings were asked to follow-up weekly.

Results
Of the 600 patients diagnosed with dengue, 375 (62.5%) were men and 225 (37.5%) were women Figure -1) with mean age of 32 years (20-60 years) (Figure -2). All patients presented with fever, with 550 (92%) patients presenting with myalgia. Other uncommon systemic findings were vomiting, lumbosacral pain, and bleeding gums. Retrobulbar pain was present in 195 (32.5%) patients and 520 (87%) patients were found to have marked thrombocytopenia <50,000/µl. Ocular manifestations were seen in patients with thrombocytopenia <35,000/µl [ Figure 3] with maximum in range between 15,000/µl and 35,000/µl. Other uncommon anterior segment findings were conjunctival chemosis and anterior uveitis. Posterior segment findings were present in 80 patients (13.3%), of which 14(87.5%) had peripheral retinal hemorrhages. Other uncommon findings were retinal vasculitis, cotton wool spots and hard exudates. Only one patient had optic neuritis [ Figure  6]. Of the 340 patients having ocular manifestations [ Figure 4], 300 patients who could be followed up had completely resolved ocular findings within 8-10 weeks. It was mainly attributed to the improving platelet counts.

Discussion
Dengue is one of the most important emerging viral diseases affecting the humans, especially in Southeast Asian countries posing a public health problem. 10 It is a communicable disease transmitted by the bite of an Aedes mosquito infected with any one of the four dengue viruses (DEN-1, DEN-2, DEN-3, and DEN-4). Recovery from infection by one provides lifelong immunity against that particular serotype. Subsequent infections by other serotypes increase the risk of developing severe dengue (previously known as dengue hemorrhagic fever). 1 The mechanism of the varied ophthalmic manifestation of dengue fever ranging from subconjunctival haemorrhage to optic neuritis is not well known but indicative of an immune mediated process and possibly infective aetiology. 11 The causes of haemorrhage could be thrombocytopenia with coagulation defects, capillary fragility, consumptive coagulopathy, and platelet dysfunction. 12 Generally, there is complete resolution of ocular changes in dengue fever.
Ocular manifestations reported to be associated with dengue infection are mostly posterior segment, such as macular oedema, vascular occlusion, vitreous haemorrhage, optic neuropathy, chorioretinitis, vasculitis with retinal haemorrhages and cotton wool spots. 4,5,8,13,14 Anterior segment manifestation has been mostly reported in the form of subconjunctival haemorrhages and anterior uveitis. 15,16 Other very rare associations are ptosis, periorbital ecchymosis and globe rupture. 3,17,18 Our study is similar to that by Kapoor et al. 15 and Hussain et al. 3 with regard to male preponderance. The mean age group of our study is 32 years that is also similar in other studies. 3,15 A total of 87% of our patients had platelet count<50,000/µl and all our patients with ocular complications had platelet count of <35,000/µl as compared to the study reported by Kapoor et al., 15 which had 90.7% of similar association. The onset of ocular manifestations in our study correlated with the nadir of thrombocytopenia as seen in other studies. 3,9,13,18 The most common ocular manifestation in our patients was subconjunctival haemorrhage followed by retinal haemorrhages. It was similar to the studies by Kapoor et al. 15 and Hussain et al. 3 however, in contrast, one patient presented with optic neuropathy in our study.
Less common findings were anterior uveitis and conjunctival chemosis, hard exudates, cotton wool spots and retinal vasculitis. In our study, the ocular findings were varied involving both anterior and posterior segments in contrast to study reported by Lim et al. 8 where in the ocular features were mainly limited to the macula.
None of the patients in our study presented with bilateral periorbital ecchymosis or unilateral ptosis and proptosis, secondary to anterior orbital and retrobulbar haemorrhage, respectively, or globe rupture as compared to other previously reported studies. 3,15 The patients in our study even included patients with diabetes and hypertension, so the retinal manifestations per se could not be attributed to dengue fever, but just as an association with dengue fever that forms a limitation to our study. Because there is expected increase in epidemicity of dengue fever, hence even the ophthalmic manifestations are expected to rise, so the treating physician should be aware and promptly refer any such case to the ophthalmologist as early as possible.

Conclusion
Dengue fever can result in varied ocular manifestations ranging from subconjunctival haemorrhage to optic neuropathy. Though most common manifestation is subconjunctival haemorrhage, retinal haemorrhages can also occur. Hence, thrombocytopenia should be corrected at the earliest to avoid ocular complications.