The findings came as the city recorded 7,685 cases yesterday, taking the official tally infected over the course of the fifth wave to 1.1 million though experts believe the actual figure could reach up to four million.

After evaluating 228 recovered patients and 109 healthy age-matched participants, researchers from CUHK's department of ophthalmology and visual sciences found that those who recently recovered from Covid are at higher risk of suffering from dry eye symptoms. Researchers further concluded that the risk of experiencing symptoms is linked to the severity of the infection.

The syndrome significantly impairs daily social and physical functions, researchers said, adding that those afflicted find it difficult to perform tasks such as reading and driving. The syndrome also makes it difficult to use digital devices.

During the study, all participants underwent eye exams such as evaluations for meibomian gland dysfunction - the most common cause of the syndrome - and corneal fluorescein staining.

Among recovered patients, 48.9 percent showed positive corneal fluorescein staining compared with 38.6 percent among healthy individuals.

Additionally, 21.5 percent of recovered patients developed at least one of the symptoms. The most common symptom was blurry vision, which occurred in 9 percent of recovered patients.

Patients who received oxygen therapy while hospitalized also experienced higher rates of tear evaporation. Further, a higher viral load corresponds with an increased risk of dry eye symptoms during the first month after recovery.

"The findings suggest the risk of tear-film instability after recovery is associated with the severity of the acute infection," researchers said.