Clouded Vision: An Introduction to Cataracts

Cataract timeline

Cataracts have been around since the Axial age, before 500 B.C. The first documented case was a surgery by Indian surgeon Sushruta and have been prevalent in medicine ever since. Cataracts are the number one cause of blindness in the world, so it is obvious why studying them is extremely important1. Cataracts are defined as lens opacities, derived from the fact that they look like a white spot has covered part of the eye, similar to what an egg white might look like. It could be anywhere from a small speck, to covering the whole pupil. 

Cataracts affect the lens of the eye. The lens helps focus light onto the retina, which converts light signals to electrical signals so the brain can interpret them. The lens is located directly behind the pupil, so the cataract is visible through the pupil as demonstrated in Figure 1. 

I’m sure most of you readers have heard of cataracts before, known someone with them, or may have had them yourselves! You might even be aware of some of their symptoms. Cataracts are most primarily marked by the presence of the white film as I stated, which can impair the vision in a multitude of ways. They are able to lead to blurry vision and even the complete loss of sight if severe enough2. I’m sure you can imagine that if you have a huge white blob covering your eye that it could heavily impact your ability to see. It is comparable to looking through a fogged up window or dashboard. Cataracts can cause objects to seem dimmer, affect night vision, a sensitivity to light, and double vision. Changing glasses and prescriptions can help some of these symptoms, but once cataracts begin to disturb your daily activities it is usually time to take care of the issue through surgery. Cataracts can be harmless, but typically the problem worsens over time and can cause complete blindness if not treated. Clinicians can identify cataracts through the physical appearance by a routine eye exam where they examine the eye’s structures with a slit lamp2. If you have been to the eye doctor, you may have been in this position where a strong light is shined in your eye and your are told to look at the doctors’ ear/earring to keep your eye focused and open (usually causing you to get a little teary eyed, in my personal experience). This allows them to better see the severity of the white blob rather than just by the naked eye. 

The lens is made up of mostly proteins, which help focus the light onto the retina. The most important structural proteins in the eye are called crystallin proteins, which make up 90% of the proteins in the eye4. They have to be tightly packed in order to correctly refract the light onto the retina. Ironically, these proteins do not even form crystals as this would create alternate paths for the light, in fact they do the exact opposite. There are three different types of crystallins with two being purely structural, while the other has the ability to prevent the formation of large clumps of proteins. These clusters of proteins are called aggregates and are very dangerous to the health of the eye. α-, ꞵ-, and 𝛾-crystallins all have the structural component to direct light, while only α-crystallins protect the structure of other proteins in the cell, including the ꞵ- and 𝛾-crystallins5. Crystallin proteins are made at birth, and do not undergo any regeneration so they have to last your whole lifetime! It is easy to see how this can lead to issues with your eyes if these proteins are altered in some way and stop working. 

Cataracts can either occur at birth or a young age, called congenital cataracts, or later in life due to aging. Each type of cataract can have various causes. Congenital cataracts may occur due to medications of infections the mother experienced or be inherited. Inherited cases account for 10-25% of congenital cataracts and cause changes to the genes for crystallin proteins4. This causes them to be unable to direct light correctly or the breakdown of proteins by α-crystallin and cause the buildup of crystallins into the white blob you may see. In cataracts due to age, modifications can be made to the proteins over time which alters their structure and prevents them from performing their job1. Additionally, microstructures of the cell such as vacuoles can change the refraction of light and change the ability to see. Vacuoles are structures of cells which hold liquid, so an increased number of them can alter light scattering and cause visual impairment. This in turn can compromise the health of the cell and lead to precipitation of proteins and worsen the issue. 

Different causes of cataracts additionally form in different areas of the eye – nuclear, cortical, and posterior. Cortical cataracts most often are associated with the cell membrane health, nuclear with the breakdown of proteins, and posterior with medication side effects, trauma, and other eye issues6.

Thank you so much for reading and I encourage you to check out the rest of my blog for further in-depth content about cataracts!

Table of Contents

Crystal Clear: The Function of Crystallin Proteins

Who Let the Cataract Out of the Bag: Discovery and Diagnosis

Mechanism of Disease

I Can See Clearly Now, the Cataracts are Gone: History of Treatment

References

  1. Bloemendal 2004
  2. https://www.mayoclinic.org/diseases-conditions/cataracts/symptoms-causes/syc-20353790
  3. https://www.aao.org/eye-health/diseases/what-are-pediatric-cataracts
  4. Hejtmancik 2008
  5. Hejtmancik 1998
  6. Chylack 1993

6 Replies to “Clouded Vision: An Introduction to Cataracts”

  1. Wow! I was unaware cataracts were able to form as large as the whole pupil. I was also unaware how important these crystallin proteins are to the makeup of the lens. Is there anything we can do to protect these proteins? Has the number of cataract surgeries increased throughout the years? Is there evidence that computer or phone screens contribute to the formation of cataracts?

    1. Thanks so much for your comment! Yes – the crystallins are the most abundant protein in the eye and a lot of the reason we can see the way we do! Actually, if you refer to this page of my blog http://victoriabasciano.bergbuilds.domains/crystal-clear/diagnosis/
      I have laid out some risk factors that can help the general health of our eyes, which is just having a balanced diet of fruits and vegetables as well as decreasing smoking and alcohol intake. Cataract surgeries have been the number one performed surgery in the US, and is in fact steadily increasing. As the population and age of older people begin to increase, because of the factors I already laid out in this post it just makes cataracts more likely and more severe, causing the need for surgery. As you can see by these graphics https://www.nei.nih.gov/learn-about-eye-health/resources-for-health-educators/eye-health-data-and-statistics/cataract-data-and-statistics the incidence of cataracts will continue to increase.
      Also located on my diagnosis page, I talk about how carotenoid antioxidants found in certain vegetables can actually counteract the blue light our screens give off. The blue light causes damage to our eyes by increasing oxygen species that can harm the proteins and other components of our cells, and the red pigment of carotenoids (most associated with carrots) can counteract that effect by using the oxygen in other reactions. I hope that was informative, please let me know if you have any other questions! 🙂

  2. This was a fascinating and informative read, teaching me a lot about the nature of cataracts! A question I had while reading was what goes into a typical cataract surgery? Are they complicated or relatively simple procedures?

    1. Thanks so much for reading! If you take a look at me treatment page victoriabasciano.bergbuilds.domains/crystal-clear/treatment I outline the history of surgery! In modern days, surgery is marked by a small incision which breaks the lens of the eye so the cataract can be extracted, and can be performed via lasers. Artificial lenses are inserted which can mimic the refraction of light that the crystallins perform and improve vision dramatically. Ophthalmic devices are also used to keep the rest of the eye structures in place. Typically surgery only lasts about ten minutes! I hope this was helpful 🙂

  3. Congratulations Victoria! This is a great blog! I didn’t know that cataracts could be congenital! “ Congenital cataracts may occur due to medications of infections the mother experienced or be inherited. ” very interesting fact! You are going to be a great optometrist! I saw the power in you since the first day I met you!

Leave a Reply to Giuseppe Cancel reply

Your email address will not be published. Required fields are marked *