"That Winter, The Wind Blows" In the story, it is said that Song Hye Kyo lost her vision to a condition called RP. Then, what exactly is RP?

In the SBS drama "That Winter, The Wind Blows", the main female character Oh Young (Song Hye Kyo) is featured as a blind heiress. Oh Young's condition has been identified as RP, also known as Retinitis Pigmentosa.

Retinitis Pigmentosa (RP) is the gradual loss of retinal cells that are light-sensitive. These retinal cells are called rods and cones. It is the damage of the retina, which is the layer or tissue located at the back of the eye. It is used to convert light images to nerve signals, which are sent to the brain. The specific cause of Retinitis Pigmentosa has not been found but most cases were found to be inherited or genetic. Retinitis Pigmentosa has been reported to be one of the three main causes for blindness, along with Glaucoma and Diabetic Retinopathy.

People who develop Retinitis Pigmentosa have a hard time adjusting to dark places and their contrast sensitivity begins to get weaker. With the loss of vision in dark places, their peripheral vision begins to get narrower and narrower. As a result, people with Retinitis Pigmentosa often see as though they are looking at a small tube and when the disease advances in the later stages, people see things squished or distorted. Aside from these symptoms, patients with Retinitis Pigmentosa may become extremely sensitive to light and some even lose their vision completely.

It is hard to cure Retinitis Pigmentosa completely but the symptoms may be lessened by the use of glasses. Also, sunglasses may be used to prevent light sensitivity. Only small number of treatments is currently available but none of them are guaranteed to completely cure this disease.

It is high recommended to always wear sunglasses in the run to protect the retina from ultraviolet light to preserve vision.

Source: https://health.chosun.com/site/data/html_dir/2013/03/28/2013032801639.html