Cat keeping one eye closed

my cat is keeping one eye closed, the following picture is when she opened a bit and I took a picture but she’s keeping it closed.   it’s her left eye, it started today. tia

Hello!   It looks as though your cat has a sore eye.  Possibly reasons for this include eyelashes protruding onto the eye's surface, ulcers / erosions / scratches of the cornea, foreign bodies / dust, pain, neurological changes e.g. disturbances to the nerve supplying the eyelid.   As your vet will probably tell you, painful eyes are often emergencies because they can deteriorate and often need be seen relatively fast.  Therefore it would be a good idea to call your vets or their emergency team for triage.