Theory of Vision (Visual Field Space)

Hello Everyone,

Welcome to my blog, i hope you and your families are staying safe and adhering to all health protocols put in place to combat the pandemic. Remember that it is not over until it is over.

So today am going to talk briefly about how our visual system takes information from the visual space or environment and how it is sent along the pathway to the visual cortex. Hopefully after this post you will be able to understand some few things about your vision and perhaps what may be happening if you are having difficulties with a particular part of your visual field

Introduction

So for most of us who may have already read some of my previous post you may be familiar with the visual pathway by now, however; let's go through it once again.

When we are looking at an object in our environment, the object emits light stimulus which goes into our eye unto the part we call the retina. On the retina, the energy is converted to electricity via a process known as phototransduction after which it goes to the optic nerve through the lateral geniculate body (LGN) to the visual cortex.

Now the question to ask is, how does the system know that this part of the impulse transmission is for this part of the visual space? To understand this better, imagine your environment space as a circle and consider you retina also as a circle. Draw lines through them to form quadrants. Now this applies to both eyes. Each quandrant of the retina sees the inverse on your visual space. So your the lower part of the your retina circle will see the upper part of your visual space and vice versa. You upper right quadrant will see lower left quadrant on your visual space. Hope you are getting it?

The Visual Fields, The Retina and the Brain

Now lets look at the more tricky part, the impulse transmission. The optic nerve sends the information as we have already discussed for the retina such that the nasal fibres hold information for the temporal visual space and vice versa. Meaning your right eye's nasal fibers has information for your right eye's temporal space and your left eye's nasal fiber's have information for your left' eye's temporal space. Same thing for the temporal fibers.

At the LGN there is partial decussation of fibers. What this means is that, nasal fibers coming from each eye moves to the opposite end to join the temporal fibers of the eye eye. This results in fibers carrying information for one part of the visual field being together. For instance the nasal fibers of the right eye and the temporal fibers of the left eye goes to the left side of the brain and has information from the right visual space for both eyes. So in the end we end up having information for our right visual space going to the left side of the visual cortex and the left going to the right of the visual cortex of the brain.

I hope you get the concept now, so this theory will be applied to why one may loss a part of vision in a particular field of his or her vision whereas the other part remains intact but we will treat that another day. As i already mentioned this theory may sometimes be confusing so take another read if need be to get the whole concept.

Image Source

Conclusion

The complexity and simplicity of vision and the visual pathway is always a interesting. Until next time i hope you enjoyed some new knowledge. Do report all ocular cases and emergencies to your optometrist. Seek information from the right source and if you need any clarification on any eye health topic i would be glad to help in the comment section.

Thanks for reading and have a great day, Special thanks to my mentors and supporters @mcsamm, @tj4real, @armandosodano, @delilhavores, @gentleshaid, @agmoore. For further reading;

https://cybersight.org/portfolio/webinar-visual-field-interpretation/
https://lucian.uchicago.edu/blogs/mediatheory/keywords/visual-field/
https://www.aao.org/bcscsnippetdetail.aspx?id=231d723d-e80f-4254-b3f0-1f4fa3e9421e