What are Ocular Sensory Neurons?

Ocular sensory neurons are fundamental to our ability to see and interact with the world around us. These specialized neurons not only convert light into the neural signals that form the basis of vision but also detect mechanical stimuli such as touch and pain, protecting the eye from injury.

Here, Creative Biolabs will explore the fascinating world of ocular sensory neurons and delve into their complex structure and function, aiming to illuminate the critical roles they play in vision and eye health.

Sensory Neurons in Vision

Ocular sensory neurons are vital components of the visual system. They convert light and mechanical stimuli into neural signals that the brain processes to create images and protect the eye. These neurons include retinal ganglion cells, photoreceptors (rods and cones), bipolar cells, and corneal nerves. Together, they ensure we perceive light, color, depth, and motion clearly.

Sensory Neurons Structure Decoded

The anatomy of ocular sensory neurons is complex and delicate, including cell bodies, axons and dendrites.

• Cell body: located in the inner layer of the retina, it is the main metabolic center of the neuron.
• Axons: extend from the cell body and are responsible for transmitting signals to other neurons or target areas. For example, the axons of retinal ganglion cells form the optic nerve, which transmits visual information to the brain.
• Dendrites: receive signals from other neurons and are involved in signal integration. For example, dendrites of bipolar and horizontal cells receive signals from optic rod and cone cells.

RGCs are important representatives of the sensory neurons of the eye, whose axons converge through the optic disk to form the optic nerve, which ultimately connects to the visual cortex of the brain. Corneal nerves, on the other hand, are distributed on the ocular surface and are responsible for the transmission of pain and touch.

Sensory Neurons Function

Ocular sensory neurons convert light signals and mechanical stimuli into neural signals through the following mechanisms:

• Photoreceptor transduction mechanism: photoreceptors (e.g., optic rod and cone cells) capture light signals via photosensitive proteins and convert them into electrical signals. This process involves G-protein activation and the opening and closing of ion channels.
• Signal transmission: signals are transmitted to ganglion cells via bipolar cells, horizontal cells and cells without long synapses. The ganglion cells integrate these signals into action potentials that are transmitted to the brain via axons.

Retinal ganglion cells play a central role in visual signaling and are divided into two categories, ON-center and OFF-center, which respond to increased or decreased light, respectively. The corneal nerve and the ophthalmic branch of the trigeminal nerve are responsible for transmitting nociceptive and tactile signals and triggering protective reflexes.

Types of Ocular Sensory Neurons

There are significant structural and functional differences between different types of ocular sensory neurons:

• Retinal ganglion cells: responsible for integrating and transmitting visual information, divided into ON-center, OFF-center and intermediate types (intermediate cells receive signals from different directions).
• Unipolar and pseudo-unipolar sensory neurons: mainly located on the eye surface, responsible for transmitting pain and touch signals.
• Bipolar sensory neurons: located in the inner layer of the retina and are responsible for receiving signals from photoreceptors and transmitting them to ganglion cells.

Corneal Sensory Neurons & Trigeminal Network

Retinal photoreceptors convert light signals into electrical signals by the following mechanisms:

• Activation of photosensitive proteins: Photosensitive proteins in optic rod and cone cells undergo conformational changes in response to light, activating G proteins. Ion channel opening and closing: activation of G proteins leads to the opening and closing of ion channels, causing changes in the transmembrane potential, which results in an action potential.
• Signal integration: Signals are transmitted to ganglion cells via bipolar cells, horizontal cells, and cells without long synapses, and ultimately to the brain via the optic nerve.

Ocular Pain Pathways

The corneal nerve is abundantly distributed on the surface of the eye and is responsible for transmitting pain and touch signals. The ophthalmic branch of the trigeminal nerve, the first branch of the trigeminal nerve, is responsible for sensation in the upper third of the face and is involved in regulating eye movements.

Figure 1. Illustration of Phototransduction Pathways.^1,3

Ocular Pain Perception and Its Neural Mechanisms

Ocular pain perception is primarily accomplished by the corneal nerve and other sensory neurons. Diseases such as dry eye and corneal injuries activate these neurons, triggering pain perception. In addition, pain signals are transmitted to the brain via the ophthalmic branch of the trigeminal nerve, triggering a protective reflex.

Figure 2. Ventral view of the trigeminal nerve's ophthalmic branch (V1).^2,3

Ocular Sensory Neuron Research in Drug Development

Research on ocular sensory neurons has made remarkable progress in recent years, especially in the construction of ophthalmic disease models and drug screening. For example, neural stem cell differentiation technology has been widely used in therapeutic research for ophthalmic diseases. According to the latest industry data, the number of ophthalmic neuroscience research publications continues to grow, and the related market size is expected to expand significantly in the coming years.

Why Choose Creative Biolabs?

When it comes to advancing neuroscience and ocular research, Creative Biolabs stands out as a trusted partner. With over a decade of experience, Creative Biolabs offers cutting-edge services tailored to studying neuronal activity, sensory neuron differentiation, and basic neuroscience research tools.

Advanced Neuronal Activity Monitoring

Creative Biolabs provides neuronal activity monitor services using multi-electrode array (MEA) technology. This platform allows real-time monitoring of neuronal responses to stimuli, drugs, or genetic changes, delivering precise and dynamic data critical for understanding neuronal function and dysfunction.

Expert Sensory Neuron Progenitor Differentiation

Harnessing stem cell technology, Creative Biolabs offers a sensory neuron progenitors differentiation service. This service enables researchers to generate high-purity sensory neurons from induced pluripotent stem cells (iPSCs), facilitating studies on sensory neuron development, disease modeling, and drug screening.

Comprehensive Neuroscience Research Tools

To support your experiments, Creative Biolabs also provides a broad range of basic neuroscience research tools, including antibodies, assays, and cell culture kits. These resources are designed to enhance the accuracy and reproducibility of your research, accelerating discovery in ocular neuroscience and beyond.

For further research support on ocular sensory neurons, please contact us today, where we offer comprehensive technical consultation and customized services to help you solve your research challenges and move your project forward.

References

1. Tolone, Arianna, et al. "The cGMP Pathway and Inherited Photoreceptor Degeneration: Targets, Compounds, and Biomarkers." Genes, vol. 10, no. 6, June 2019, p. 453. https://doi.org/10.3390/genes10060453.
2. Ichinose, Tomomi, and Samar Habib. "On and off Signaling Pathways in the Retina and the Visual System." Frontiers in Ophthalmology, vol. 2, Aug. 2022, p. 989002. https://doi.org/10.3389/fopht.2022.989002.
3. Distributed under Open Access license CC BY 4.0, without modification.

For Research Use Only. Not For Clinical Use.