It was suggested that this comparative study indicates that in mammals the adoption of nocturnal habits may be associated with an enhancement of binocular vision. However, the authors emphasized that several nocturnal predatory birds lack binocular enhancement, and they also mentioned the New Caledonian crows (Corvus moneduloides), a diurnal bird that exhibit the largest known degree of binocular overlap among birds (60°), indicating that manipulative behaviors, may lead to an enhancement of binocularity (1).
Both these Octodon species have the ability to climb in bushes and small trees, however since Octodon lunatus is more common in thickets and Octodon degus primarily occupy grass land and flat habitat (2), climbing activities is likely to be more frequent in the former. That may provide support for an alternative hypothesis; that the need of accurate eye-forelimb coordination influenced the evolution of binocular vision in vertebrates (3). In other words that the selective value of improved climbing abilities was a driving force in the evolution of the visual system of Octodon lunatus. Evolutionary processes may change the direction of retinal ganglial cells. Crossing, or non-crossing, in the optic chiasm determines which hemisphere receives visual feedback in reaching tasks. In a typical vertebrate each hemisphere receives little tactile and proprioceptive information about the ipsilateral hand (forelimb, paw, wing, fin etc.). The eye-forelimb hypothesis proposes that abundant ipsilateral retinal projections (IRP) developed in the primate brain to synthesize, in a single hemisphere, visual, tactile, proprioceptive, and motor information about a given hand, and that this improved eye-hand coordination and optimized the size of the brain (4). The primate visual system is ideally suited for tasks within arm’s length and in the inferior visual field, where most manual activity takes place. Altering of ocular dominance in reaching tasks, reduced cross-modal cuing effects when arms are crossed, response of neurons in the primary motor cortex to viewed actions of a hand, multimodal neuron response to tactile as well as visual events, and extensive use of multimodal sensory information in reaching maneuvers support the premise that benefits of accurate limb control influenced the evolution of the primate visual system (4). The nocturnal restriction hypothesis applies mainly to mammals, while the EF-hypotheis seems to be applicable to vertebrates in general (3). Therefore a comparative study of the visual systems and the association with climbing abilities in Octodon species would be of large interest.

References:
1. Troscianko J, von Bayern AM, Chappell J, Rutz C, Martin GR (2012) Extreme binocular vision and a straight bill facilitate tool use in New Caledonian crows. Nat Commun 3: 1110. doi: 10.1038/ncomms2111
2. Encyclopedia Brittanica
3. Larsson M (2011), Binocular vision and ipsilateral retinal projections in relation to eye and forelimb coordination, Brain Behav Evol, 77:219-230.
4. Larsson M (2013), The optic chiasm: a turning point in the evolution of eye/hand coordination, Front Zool, 10:41 doi:10.1186/1742-9994-10-41