The key to the exceptional night vision of the nocturnal helmet gecko is a series of distinct concentric zones of different refractive powers, according to a study published in the Association for Research in Vision and Ophthalmology's peer-reviewed, online Journal of Vision ("The pupils and optical systems of gecko eyes," http://www.journalofvision.org/9/3/27).
This multifocal optical system is comprised of large cones, which the researchers calculated to be more than 350 times more sensitive than human cone vision at the human color vision threshold.
"We were interested in the geckos because they – and other lizards – differ from most other vertebrates in having only cones in their retina," said project leader Lina Roth, PhD, from the Department of Cell and Organism Biology at Lund University in Sweden. "With the knowledge from the gecko eyes we might be able to develop more effective cameras and maybe even useful multifocal contact lenses."
The nocturnal geckos' multifocal optical system gives them an advantage because light of different ranges of wavelengths can focus simultaneously on the retina. Another possible advantage of their optical structure is that their eyes allow them to focus on objects at different distances. Therefore the multifocal eye would generate a sharp image for at least two different depths. Geckos that are active during the day do not possess the distinct concentric zones and are considered monofocal, Roth said.
The scientists also developed a new method to gather optical data from live animals without harm with their modifications to the Hartmann-Shack wavefront sensor.
"Studies of animals with relatively large eyes, such as owls and cats, have included surgery and fixation of the head," the article states. "In this study, we demonstrate that it is possible to obtain high-resolution wavefront measurements of small, unharmed gecko eyes without completely controlling the gaze or the accommodation of the animal eyes."
The Journal of Vision is an online-only, peer-reviewed publication of the Association for Research in Vision and Ophthalmology (ARVO). Access to articles is free and open to anyone. See www.journalofvision.org.
ARVO is the largest eye and vision research organization in the world. Members include more than 12,000 eye and vision researchers from 73 countries. The Association encourages and assists research, training, publication and dissemination of knowledge in vision and ophthalmology.
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