Through New Eyes

Clinical experience cuts restraints of Ethical Committees. Here I report an observation impossible to make under the auspices of research, but available to any of us as we get older, since the remarkable clinical technique of replacing the eye's lens made cloudy by cataract with a new highly transparent artificial lens. This remarkably successful procedure was developed very much by one man: Nicholas Harold Lloyd Ridley (1906 ^ 2002). Ignoring the warnings of his colleagues of dire results, Ridley pushed ahead, to unqualified success. Many thousands owe him a debt of gratitude for their new lease of sight. In a way, this is two leases of sight, for generally the operation (which takes only a few minutes, without a stay in hospital) is performed initially on one eye, and then after several months on the other. My right eye was re-lensed just over a year ago, and the left eye exactly a month ago. Following the first operation, I noticed quite marked changes of colours, especially blues being brighter. They seemed brighter compared with memory, and also by contrast to the unoperated left eye. This may not seem surprising, as a yellow filter had been removed from the right eye but remained in the left eye. The situation for the second cataract operation is quite different. For now the comparison is with no yellow filter in either eye. The situation is optically symmetrical. What I observed was very striking. The evening sky was heavy gray cloud; but, with the new left eye, it appeared science-fiction purple. It looked like an artist's vision of an alien planet in a science-fiction story, the sky was so intensely purple. As it happened, the evening sky remained cloudy and gray for nearly a week. The purple sky of the new left eye continued, evening after evening, gradually becoming less vivid. Now, a month later, there is still a marked difference between the eyes, through the science-fiction purple has almost gone. This must surely be long-term central adaptation, to the yellow filter of the cataract. Is this monocular colour adaptation for the second eye well known? It should be entirely possible to measure and track the gradual loss of the effect by colour matching. My impression is that the effect is most striking in somewhat dim conditions. The blue sky of mid-day did look different with the new eye; but not as striking as the purple of the evening gray cloud. There must be several experiments worth trying after a cataract operation. Can the Pulfrich pendulum effect be given by central adaptation to monocular loss of light? Would it be different for different colours, greater in blue light? It would be surprising for darkadaptation-associated delay to be centrally compensated, but perhaps just possible. (There have been attempts to measure this in Oxford and Bristol, but I believe not conclusively.) Does the visual brain lose, then after the operation increase, effective acuity, to match changes of resolving power of the eye? I certainly hope so. (The retinal resolution of Nautilus is supposed to be higher than the optical resolution of its pinhole eye. Is this really so? Should it give Darwin another of his cold shudders, if the retina is too good?) In cataract operations, is there a case for improving the optics of the natural lens? Would providing chromatically corrected lenses improve on nature? It would be a wonderful joke if one saw reversed colour fringes; from previous adaptation, or from built-in neural compensation to normal chromatic aberration. But as we do not see chromatic fringes in monochromatic light this seems unlikely. Editorial Perception, 2002, volume 31, pages 899 ^ 900