Can Glial Cells Act as Living Optical Fibers in the Retina?

  • Thread starter peter.ell
  • Start date
  • Tags
    Work
In summary, the conversation discussed how vertebrates, including humans, are able to see despite their photoreceptors being pointed away from the light. The presence of glial cells in front of the retina acts as fiber optic cables, channeling the light to the photoreceptor cells. This phenomenon is further explained in the paper by Franze et al. (2007), which shows that Müller cells, a type of glial cell, have a higher refractive index and are oriented along the direction of light propagation, effectively minimizing distortion and loss of light. This discovery highlights a new function of glial cells and sheds light on the inverted retina as an optical system.
  • #1
peter.ell
43
0
I'm wondering how it's possible for vertebrates like us to see so well, or at all, if our photoreceptors are actually pointed away from the light focused on the retina. I would assume that the light would just pass right by the photoreceptors and we wouldn't be able to see much except for the presence or absence of light.

The fact that photoreceptors are pointed away from the light seems like it wouldn't allow for good vision similar to how you can't see the sun if your head is turned away from it. Yet it works for us and many other vertebrates with even better vision but the same design. How?
 
Biology news on Phys.org
  • #2
Part of the answer seems to be that some of the glial cells in front of the retina act like fiber optic cables to channel the light from the retina to the photoreceptor cells. See the following paper:

Franze et al. (2007) Müller cells are living optical fibers in the vertebrate retina. Proc Natl Acad Sci USA 104(20): 8287. http://dx.doi.org/10.1073/pnas.0611180104, PMC:1895942

Abstract:
Although biological cells are mostly transparent, they are phase objects that differ in shape and refractive index. Any image that is projected through layers of randomly oriented cells will normally be distorted by refraction, reflection, and scattering. Counterintuitively, the retina of the vertebrate eye is inverted with respect to its optical function and light must pass through several tissue layers before reaching the light-detecting photoreceptor cells. Here we report on the specific optical properties of glial cells present in the retina, which might contribute to optimize this apparently unfavorable situation. We investigated intact retinal tissue and individual Müller cells, which are radial glial cells spanning the entire retinal thickness. Müller cells have an extended funnel shape, a higher refractive index than their surrounding tissue, and are oriented along the direction of light propagation. Transmission and reflection confocal microscopy of retinal tissue in vitro and in vivo showed that these cells provide a low-scattering passage for light from the retinal surface to the photoreceptor cells. Using a modified dual-beam laser trap we could also demonstrate that individual Müller cells act as optical fibers. Furthermore, their parallel array in the retina is reminiscent of fiberoptic plates used for low-distortion image transfer. Thus, Müller cells seem to mediate the image transfer through the vertebrate retina with minimal distortion and low loss. This finding elucidates a fundamental feature of the inverted retina as an optical system and ascribes a new function to glial cells.
 

1. How does light enter the retina?

The retina is located at the back of the eye and is made up of light-sensitive cells called photoreceptors. Light enters the eye through the cornea, passes through the pupil, and then through the lens. The lens helps to focus the light onto the retina, specifically the macula, which is responsible for central vision.

2. What is the role of photoreceptors in the retina?

Photoreceptors, specifically rods and cones, are responsible for converting light into electrical signals that can be interpreted by the brain. Rods are more sensitive to low light and are responsible for peripheral and night vision, while cones are responsible for color and central vision.

3. How does information from the retina reach the brain?

The photoreceptors in the retina are connected to nerve cells called ganglion cells. These ganglion cells then transmit the electrical signals from the photoreceptors to the brain through the optic nerve. The brain then interprets these signals to create the images we see.

4. What is the role of the retina in vision?

The retina is essential for vision as it is responsible for capturing and processing visual information. It converts light into electrical signals and transmits them to the brain for interpretation. Without a functioning retina, our ability to see would be greatly impaired.

5. How does the retina adapt to changes in light levels?

The retina has a specialized layer of cells called the retinal pigment epithelium (RPE) that helps to regulate the amount of light that reaches the photoreceptors. The RPE can adjust the size of the pupil and the sensitivity of the photoreceptors to adapt to changes in light levels. This allows us to see clearly in both bright and dim lighting conditions.

Similar threads

Replies
4
Views
2K
  • Biology and Medical
Replies
1
Views
2K
  • Biology and Medical
Replies
17
Views
8K
Replies
22
Views
2K
Replies
1
Views
1K
Replies
2
Views
996
Replies
9
Views
2K
  • Classical Physics
2
Replies
37
Views
2K
Replies
2
Views
5K
Back
Top