Evolution of Sight in the Animal Kingdom

This amazing video produced by the History Channel, Vision and Evolution of the Eye is well worth 40 minutes of your time.  The evolution of visual systems is something that we here at Webvision are very interested in.  Also note that we have an excellent chapter on the Evolution of Phototransduction, Vertebrate Photoreceptors and Retina by Trevor Lamb here on Webvision.

 

This accompanying text below on this post was sent to us by friend of Webvision, Dr. Dominic Man-Kit Lam.  Dr. Lam was born in Swatow, and grew up in Hong Kong. He studied under two Nobel Laureates at Harvard Medical School before joining the Harvard Faculty and subsequently became Professor of Ophthalmology and Chairman of Center for Biotechnology at Baylor College of Medicine in Houston. He is the president of the World Eye Organisation, A charitable organization dedicated to the prevention and treatment of eye disorders for the poor.  Continue reading “Evolution of Sight in the Animal Kingdom”

The Blind Woman Who Sees Rain, But Not Her Daughter’s Smile

“Once her belief was sanctified by science, her sight got better and better…”

I first read about blindsight back in high school, reading an essay by Oliver Sacks and was absolutely intrigued by the thought of seeing without sight. Now there is a wonderful vignette on NPR by Lulu Miller that talks about blindsight (be sure to listen to the story on All Things Considered).

Of course we know now that there are multiple visual pathways and each one of these visual pathways mediates a different aspect or derivative of a component of vision.  It turns out that vision is complex, more complex than simply carrying “visual pixels” to the brain to be mapped out topologically.  After photon capture by the photoreceptors of the eye and pre-processing operations in the circuitry of the retina, information is passed to the retinal ganglion cells or the output cells of the retina.  Each one of the 18-20 types of ganglion cells that project out of the retina through the optic nerve mediates different kinds of information.  Aside from projections to the primary visual cortex, some ganglion cells project to the lateral geniculate nucleus, others to the superior colliculus, the pretectum, the suprachiasmatic nucleus and the hypothalamus.  Each one of these projections out of the retina carries information relevant to a different feature of vision.  Some of these functions help control the size of your pupil limiting the amount of light that comes into the eye.  Other projections help you orient your head and eyes to the world around you while other projections still help you figure out what time of day and season it is.  Most of these meta-visual functions are not conscious, but play crucial roles in how we live our everyday lives and are only revealed when things in the visual system go awry like the man Oliver Sacks described who could catch a ball despite being completely and functionally blind.  Milena Channing’s experience with a stroke in her visual cortex reveals some of this unconscious aspect of seeing, ironically by causing blindness while preserving portions of the brain involved in motion detection.

 

Abstract Human Retina

Human-color-retina

This image of ganglion cellsMüller cells and starburst amacrine cells in the human retina is from a patient suffering from retinitis pigmentosa (RP).  This disease this patient suffered from slowly causes people affected with this disease to go blind and is a constant reminder to me of why we engage in our research.

For some, this is a pretty, though abstract image created through a set of technologies called computational molecular phenotyping (CMP).   The colors in this image come from antibodies labeling taurineglutamine and glutamate, all small molecular species that reveal metabolic states in these tissues.

For us, these images reveal variation in cell types as well as abnormalities in other kinds of cells that presage retinal stress and the cellular responses that alter the retina in ways that both cause blindness and make it difficult to rescue vision loss.  We also see the beginnings of changes in the circuitry of the retina that forever will alter the way that diseased retinas process information.

Image courtesy of Bryan William Jones, Ph.D. and originally appeared here.

Notable Paper: Retinal Remodeling in the Tg P347L Rabbit, a Large-Eye Model of Retinal Degeneration

This paper is the result of a collaborative effort between Bryan William Jones, Mineo Kondo and Hiroko Terasaki, Carl Watt, Kevin Rapp, James Anderson, Yanhua Lin, Maggie Shaw, Jia-Hui Yang and Robert Marc.

This work presents a substantial advance in models of Retinitis pigmentosa (RP), an set of inherited blinding diseases characterized by progressive loss of retinal photoreceptors.   Continue reading “Notable Paper: Retinal Remodeling in the Tg P347L Rabbit, a Large-Eye Model of Retinal Degeneration”