Disagreement on whether the evolution of the camera eye within cephalopods and within vertebrates is a parallel evolution or a convergent evolution still exists, although is mostly resolved. The current standing is that of a convergent evolution for their analogous camera-type eye.
Those maintaining that it is a parallel evolution state that there is evidence that there was a common ancestor containing the genetic information for this eye development. This is evidenced by all bilaterian organisms containing the gene Pax6 which expresses for eye development.
Those supporting a convergent evolution state that this common ancestor would have preceded both cephalopods and vertebrates by a significant margin. The common ancestor with the expression for camera-type eye would have existed approximately 270 million years before the evolution of camera-type eye in cephalopods and approximately 110 to 260 million years before the evolution of camera-type eye in vertebrates. Another source of evidence for this is the differences of expression due to independent variants of Pax6 arising in both cephalopods and vertebrates. Cephalopods contain five variants of Pax6 in their genomes which independently arose and are not shared by vertebrates, although they allow for a similar gene expression when compared to the Pax6 of vertebrates.

The main medical use emerging in this field is for research on eye development and ocular diseases. New research studies on ocular gene expression are being performed using cephalopod eyes due to the evidence of their convergent evolution with the analogous human eye. These studies replace the previous Drosophila studies for gene expression during eye development as the most accurate, although Drosophila studies remain the most common. The conclusion that they are analogous lends credibility to their comparison for medical use in the first place, since the trait in both would have been shaped through natural selection by similar pressures in similar environments; meaning there would be similar expression of ocular disease in both organisms’ eyes.

An advantage of cephalopod eye experimentation is that cephalopods can regenerate their eyes due to their ability to re-enable their developmental processes, which allows studies of the same cephalopod to continue past one trial sample when studying the effects of disease. This also permits for a more complex study concerning how regeneration may be conserved in cephalopod genomes and if it may be somewhat conserved in the human genome alongside the genes expressing for the camera eye.

• Mollusc eye
• Octopus senses
• Squid nervous system
• Evolution of the eye