Cone Cells: Anatomy, Types, Function, and Associated Eye Problems

What is Another Term for Cone Cells?

Another term for cone cells is photoreceptors. According to Merriam-Webster, the term photoreceptor is defined as a receptor for light stimuli and is used when referring to what helps us see colour (cones) and vision in low light (rods).

Where are the Cone Cells Located in the Eyes?

The cone cells are located in the light-sensitive layer at the back part of the eye, known as the retina. The cone cells are specifically located in the fovea, which is the centre of the macula lutea, according to the National Institutes of Health.

1. L Cones

L cones are commonly known as red-sensing cones and help us see red colours. The function of L cones is to absorb longer wavelengths. Red lights possess the least amount of energy compared to other visible light, which amounts to 560 nm, therefore, red lights produce the longest wavelengths.

2. S Cones

S cones are referred to as blue-sensing cones, which help us see blue colours. Blue light has the highest amount of energy, therefore, causing shorter wavelengths to absorb. These shorter wavelengths measure around 420 nm.

3. M Cones

M cones help us to perceive green colours, in turn, they are known as our green-sensing cones. M cones absorb wavelengths of around 530 nm, making them medium wavelengths.

What Colours do Cone Cells Detect?

The colours that cone cells detect are red, green and blue. The different types of cone cells each function to detect different colours, with L cones detecting red colours, S cones detecting blue colours and M cones detecting green colours. The combination of these cells’ signals assists the brain in differentiating between a plethora of different colours, according to the National Institutes of Health.

How Many Cone Cells are in the Human Eye?

There are around 6 million cone cells in the human eye, according to the American Academy of Ophthalmology. These cone cells are distributed in the centre of the retina, which is known as the macula.

1. Retinitis Pigmentosa

Retinitis pigmentosa is a term used for a group of eye conditions that cause the retina’s cells to deteriorate over time. Retinitis pigmentosa is typically inherited from your parents and can bring on symptoms such as poor night vision, loss of peripheral vision and light sensitivity. There is no treatment for retinitis pigmentosa, however, using low-vision aids and rehabilitation programs may be helpful.

2. Colour Blindness

Colour blindness is an eye condition that can hinder your ability to differentiate between different colours or see certain colours. Colour blindness is inherited and may be noticeable when you are born, however, it can also occur at any age, according to the National Health Service. The most common types of colour blindness are deuteranopia and protanopia (red-green) colour blindness and tritanopia (blue-yellow) colour blindness. The more rare form of colour blindness is monochromatism, which is complete colour blindness.

3. Usher Syndrome

Usher syndrome is a rare genetic condition that impairs hearing and vision as a result of developing retinitis pigmentosa. Type one of Usher syndrome involves significant hearing loss, loss of night vision and balance problems. Type two involves moderate to severe hearing loss during early childhood and loss of night vision by teenage years. Type three causes the onset of hearing loss in childhood with normal hearing at birth, loss of night vision by teenage years and normal balance, according to the National Eye Institute. Signs of Usher syndrome can include difficulty moving around in the dark, longer need to adjust to lighting changes and stumbling over objects in their path. Early treatment such as low vision aids or hearing aids and cochlear implants may help optimise their hearing and vision.

4. Photokeratitis

Photokeratitis is an eye condition that can arise as a consequence of overexposure to ultraviolet rays from sources such as the sun, welding arcs, light reflection from snow and UV lamps. Photokeratitis can be similarly described as having a sunburn in the eye and may induce severe eye pain as one of the early signs. Other symptoms that can occur along with the eye pain may include light sensitivity, reduced vision and teary eyes. Similar to corneal abrasions, photokeratitis can heal on its own within 24-72 hours. However, other cases may require the use of topical antibiotic ointments or topical pain relief ointments, according to the American Academy of Ophthalmology.

5. Blue Cone Monochromacy

Blue cone monochromacy is a vision disorder that is inherited and affects the cones of the eye. A patient with blue cone monochromacy will not have properly functioning red and green cones but their blue cones are working normally. Symptoms of blue cone monochromacy may include light sensitivity, reduced colour vision, low vision acuity, nearsightedness and nystagmus. Blue cone monochromacy typically stems from genetic mutations and is considered a rare disease, according to the National Centre for Advancing Translational Sciences.

6. Cone Dystrophy

Cone dystrophy is the term used when the cones of the eye stop working, which can lead to loss of vision and colour vision. Cone dystrophy can be inherited through various ways and may present symptoms such as the inability to differentiate between certain colours, loss of clear vision, light sensitivity and nystagmus. According to the Macular Society, the cause of cone dystrophy and the reason why some people may have different symptoms is still not known.

What are the Eye Tests Used by Optometrists to Examine the Cone Cells?

The test used by optometrists to examine the cone cells may include an electroretinography, which measures the retina’s electrical response. Optometrists may need to perform an electroretinography (ERG) if you are showing signs of any retinal disorder or condition. The optometrist will perform this test with and without light, the activity recorded with light will come from the cones in the retina and the activity recorded in a dark room will stem from the rods in the retina.

It is important to note that Oscar Wylee does not conduct this type of test. However, our optometrists do run comprehensive eye tests that are capable of detecting a range of eye conditions.

How Important is a Regular Eye Exam for the Cone Cells?

It is very important to receive regular eye exams to help ensure all ocular structures including the cone cells are healthy. Eye exams are vital for monitoring the progress of any eye conditions you may have and looking out for any minor or major changes to your vision. Regular eye exams can help reduce or delay the progression of vision loss or other complications.

How Can Oscar Wylee Assist You with Taking Care of Your Cone Cells?

Oscar Wylee can assist you with taking care of your vision with our comprehensive eye tests and the use of modern equipment. Oscar Wylee provides eye tests available for bulk billing, which can help our optometrists with assessing the condition of different regions in the eye. You can book online or in-store to see one of our optometrists.