The main danger is that damage to the retina can occur without any immediate warning. According to ophthalmologist Germán Castilla of Xarxa Tecla, prolonged exposure to intense sunlight during an eclipse can cause solar retinopathy, potentially affecting the macula, the part of the retina responsible for central vision.
Retinal damage may appear hours later
Solar retinopathy can lead to blurred vision, distorted images, changes in colour perception and the appearance of a dark spot in the centre of vision.
Castilla explained that the absence of pain does not mean the eyes are safe. The retina does not contain pain-sensitive nerve endings, meaning a person may continue looking at the eclipse while damage is occurring without realising it.
This makes direct observation particularly dangerous, as symptoms may only become noticeable later, after retinal injury has already taken place.
Only certified eclipse glasses should be used
Ophthalmologists recommend observing the eclipse only through certified solar viewing glasses that meet the ISO 12312-2:2015 standard.
Ordinary sunglasses are not considered adequate protection for viewing the Sun directly. People should also avoid homemade filters or other makeshift solutions.
During a total solar eclipse, the glasses may be removed only during the brief period when the Moon completely covers the Sun. They must be put back on before the first rays of sunlight become visible again.
The warning comes as preparations are underway in Tarragona, where large numbers of people are expected to gather to observe the rare astronomical event.
Seek medical attention if symptoms appear
Experts advise anyone who observes the eclipse without adequate protection and later develops blurred or distorted vision, changes in colour perception or a dark spot in the centre of their vision to seek medical attention.
If visual problems continue for several hours after exposure or remain present the following day, an ophthalmologist should be consulted urgently.
The key warning from eye specialists is simple: the absence of pain during an eclipse does not mean there is no damage. Proper eye protection is essential whenever looking directly at the Sun.
