It is perhaps worth mentioning that despite laser attacks on aircraft being measured in the thousands per year around the globe, not a single crash has resulted as a result of these incidents, nor a single life lost.
That may well be due to the outstanding performance and training of professional aircrew or it may be that the disruption that such incidents cause is in fact over stated.
Anything that needlessly endangers an aircraft in flight is to be utterly condemned.
As self loading freight, I may not know much about professional flight operations, but I do know a lot about laser beams, beam divergence angles, diffraction, attenuation through glass and optical coatings and eye safety when using lasers. Other posters have already supplied sufficient details for readers to make their own assessment of the risks posed to sight from high powered optical sources aimed at an aircraft in flight.
Typically laser dazzle incidents do not result in permanent injury but may cause temporary disruption of normal vision, disorientation, confusion and eye irritation, all effects that are seriously hazardous to flight, especially in darkness.
I fully accept the crew acted in accordance with their training but question the decision to return to the departure airport rather than landing at the nearest available airport for the pilot to receive urgent medical attention. Nothing to do with the costs of providing accomodation and an onward flight for the passengers I suppose? Bean counters strike again. Heathrow is a pretty busy airport for single pilot operations, although a Pan call would facilitate matters.