The Chikungunya virus (CHIKV) can cause long lasting symptoms and manifestations. The most frequent ocular symptoms of CHIKV infection included ocular pain, inflammation and reduced visual acuity, whilst conjunctivitis and optic neuritis were the most common manifestations of the disease.
NA viruses that cause infectious diseases can cause a wide spectrum of ocular disorders . Although the most common symptoms of CHIKV infection are fever, headache, rash and polyarthralgia, the virus appears to present tropism for the nervous system in the ocular tissue . In fact, eye alterations are recognized as important complications of Chikungunya fever, although their exact characteristics had not previously been defined [40,41].
The data indicates that CHIKV infection may cause eye alterations in a quarter of the infected population. This frequency implies the relevance of these manifestations, and the possible burden they can imply in the health system and in the patient’s quality of life .
Ocular pain and inflammation, as well as visual defects were the ocular symptoms most associated with CHIKV infection. Retro-orbital pain is a frequent symptom of the viral infection which can be present in the acute phase of the disease and sometimes become persistent following disease resolution . Furthermore, the exact temporal relationship between the appearance of typical symptoms such as fever and headache and of ocular pain is unclear. Its appearance can vary depending on the ocular structure affected and the degree of ocular involvement . A range of ocular structures can become inflamed during CHIKV infection, including the choroid, uvea, nerve, vitreous, retina and retinal vessels . Even though each eye structure has its own physiology, redness of the eye has been considered as the main indicative of virus-induced eye inflammation [44,45,46].
Different types of visual defects have been linked to CHIKV infection. The decreased visual acuity is the major visual defect linked to the virus. Moderate to severe reduction in visual acuity has been observed in CHIKV-infected patients [47,48]. Reduced visual acuity has also been reported for other arbovirus infections (Zika and dengue) [49,50].
The most common ocular manifestations of CHIKV infection included corneal involvement, conjunctivitis, episcleritis, optic neuritis and uveitis. Corneal involvement was found in three patients. The corneal tissue (mainly corneal fibroblasts and corneal endothelium) is suggested to be the eye structure with the greatest viral tropism . Indeed, viral RNA was detected in the eye tissue of patients and corneal grafts from potential donors—even in one with negative serology . Keratitis is the most common form of corneal involvement .
Conjunctivitis may be the most prevalent ocular manifestation. It is observed in the acute phase of the disease  and it is the most common eye manifestation in travellers who go to countries where this arbovirus is emergent . Optic neuritis was the second most frequently reported ocular manifestation. Uveitis was another ocular manifestation identified. Patients with uveitis may present vision loss, scotoma, colour vision and peripheral field defects . This manifestation can occur either in the acute or chronic phase of the disease . Anterior uveitis (in the form of retinitis, choroiditis or neuroretinitis) is more common than posterior uveitis  which can be acute in immunocompromised patients .