Just to let you know I tried convergence exercises I found on the net with instant results. My face relaxes and my jaw doesn't close. Having experimented today I have found that left eye does not tollerate bright light. Every time I looked at my computer screen the problem came back however if I turned the brightness right down the problem went away. So from now on I will permanently turn the brightness down. Things were going well until later this afternoon and the sun appeared from behind the clouds and would you believe it the problem returned. So the convergence problem seems to occur due to a difference in tollerance for light in respect to each eye. I have also looked at photos going back many years and on sunny days I can clearly see myself squinting in my left eye.
Just wondered if this additional info helped any further in the diagnosis
I have already pressed the accept prompt as this is potentially a life changing experience for me any further guidance would be much appreciated. Once again many thanks for your contribution.