Vladimir Neroyev, the chief ophthalmologist of the Russian Health Ministry, said, "The condition of the eye tissues and structures is stable. Their state has not impaired,” the doctor said.

This proves that the surgical and conservative treatment has been effective and inspires hope that the patient will recover from the trauma, Neroyev added.

A masked assailant approached Filin outside his home on Troitskaya Street in Moscow on January 17, threw acid in his face and escaped.

Filin was admitted to hospital with burns to his face, head and eyes.

Filin has been receiving constant threats in recent months.