On June 23, Dr. Tran Anh Duong (Ophthalmology Department, Vietnam - Cuba Friendship Hospital Dong Hoi, Quang Binh), said: Some people believe in the folk remedy of putting lemon juice in their eyes and looking up at the sun on the Doan Ngo Festival (the 5th day of the 5th lunar month) to be good for their eyes. But they do not know that this action will have a very bad effect on their eyes.

Earlier, at noon on June 22, some people in Quang Binh put lemon juice in their eyes and looked straight at the sun at exactly 12 noon. According to folk beliefs, this will help keep the eyes healthy and reduce the risk of eye diseases.

Explaining the above action, Dr. Duong said that lemon juice contains many ingredients including vitamin B, C, some minerals and especially citric acid. This type of acid has a high concentration that can cause eye burns, especially in eyes with previous damage, it will make the damage worse.

"Looking directly at the sun will cause damage to the conjunctiva, cornea, and lens from ultraviolet and infrared rays. Especially damage to the fundus (mainly the macula), looking for more than 30 seconds can lead to permanent blindness," said Dr. Duong.

To make it easier to visualize, Dr. Duong gave an example of how in reality, to create fire, people use a magnifying glass (convex lens) placed under sunlight, then use paper, cotton, or wood to place in the position where the light converges below, after a while those objects will catch fire.

The eye is similar in that it is a complex of convex lenses that focus light onto the back of the eye to help us see objects clearly. When looking at the sun, the direct sunlight will focus on the macula, causing burns to the cone cells and rod cells (two light-sensitive cells).

Maybe at that time, people looking at the sun do not feel the dimness, but later, in addition to thermal burns, it also changes the biology of the cells, causing them to completely lose function, leading to blindness.

Doctor Duong also advised people to carefully consider folk concepts of disease treatment and prevention to avoid unfortunate incidents.