So the aircraft was at 8000 feet climbing out of Heathrow. The vision out the front of the cockpit will be limited towards the ground, so the laser has to be a good three miles or more away. So the pilot has been looking at a laser that was probably five miles away and with the beam width spread to several feet. The blink reflex should have prevented exposure for more than a few fractions of a second even looking directly into the beam.
An unsettling experience with dark adapted vision, but unlikely to cause any permanent damage. This is an hysterical overreaction considering that the aircraft was already out past the west coast of Eire before turning back. I'm sure the pilot that was blinded by the laser may have felt some discomfort and eye irritation, but dumping thousands of pounds worth of fuel into the environment and inconveniencing hundreds of passengers strikes me as gross incompetence on behalf of the flight crew. There were two pilots, one apparently unaffected, the other still capable of assisting within the cockpit, why not continue the flight to the destination.
This all smacks of someone trying to prove a point or with an axe to grind.
I speak as someone who has experienced high intensity laser light being shone directly into the eye. An unpleasant experience, but I regained relatively normal vision within about ten minutes and had a sore, bloodshot eye for a couple of days afterwards.
Laser pointers and other devices for sale in the UK are supposed to be restricted to powers of less than 1mW, which is regarded as "eye safe" at any distance so long as you don't stare into the beam. Higher powered devices can be obtained over the internet from Far East suppliers or by repurposing common domestic items such as computer DVD drives. It is impossible to completely regulate such items. Customs and excise do regularly seize directly imported goods, but quite a lot get through the net.