Causes of keratoconus
Causes of Keratoconus
First, there may be many causes of keratoconus that are not known to us. So we need to start with an open mind and learn about causes.
Allergies
Allergies are immune responses to external factors like dust, pollen, mold, or cat hair. Certainly, It is well documented that keratoconus patients suffer more ocular allergies than the rest of the population and that the common response is rubbing the eyeball. This is how we damage our cornea when we are young and nobody tells us we are doing something harmful.
Inflammation
Even though keratoconus is considered to be a non-inflammatory degenerative disease, this is probably not the case. When inflammation slowly persists for many years by other reasons like diet, genetic, or environmental causes, this can damage the body over time.
Keratoconus Hypothesis
The cascade Hypothesis
The cascade hypothesis 1 is one of the most accepted theories about the origin and causes of keratoconus, this keratoconus hypothesis concludes that the cornea of someone with keratoconus is exposed to factors that produce free radicals.
This creates a cascade of events that result in corneal scarring and apoptosis. This is a process in which the body instructs the cell to die so that it doesn’t interfere with other processes and functions of the whole body, (cell programmed death).
The cornea of someone with keratoconus is not normally protected against free radicals, so it is slowly damaged in the long run. The majority of adult people with keratoconus can be stable for many years and only 1 in 10 will require surgery. Your goal must be to be in that 90% who can function without surgeries.
In short this means that your keratoconus advances slowly every day if you have low enzymatic protection aggravated by other causes. These causes can be lifestyle, nutrition, and environment (contact lens) related.
Eye Rubbing Hypothesis
Keratoconus corneas are exposed to elevated enzymes that degrade proteins. These enzymes are called proteases and they increase their activity4 probably after vigorous eye rubbing5
There is also a strong relationship between the keratoconus severity and the way the person rubs his eyes. His dominant hand (right or left) “usually” means his worst condition eye, mine is. Even the position you take when sleeping can impact your vision.
All this suggests a big relationship between mechanical trauma to the cornea and the advancement of keratoconus. Meaning that if you have keratoconus probably your corneas are thinner than regular corneas but the main cause of your keratoconus worsening is unconscious eye rubbing (eye strain) during long periods of time.
It is hard to quantify eye rubbing, especially in young persons because it is a bad unconscious habit. It is paramount that you bring consciousness to how you treat your eyes so that if you are rubbing them, you stop immediately doing it.
Eye rubbing can be related to allergies, dry eye, or other conditions hard to determine.
In a French study called “the keratoconus and eye rubbing prospective online study”, evidence was found suggesting that stopping rubbing your eyes can even stop the progression of the keratoconus.
They concluded “There is a striking correlation between the more advanced side of keratoconus and the side that is rubbed more, as well as the sleeping position”
That is why I believe getting contacts and cross-linking is not enough. You need to realize how you use your eyes so you can stop bad habits like rubbing and squinting and take care of allergies and posture when you sleep.
Oxidative Stress Hypothesis
Oxidative stress is the imbalance between oxidants and antioxidants in favor of the oxidants2. One of the areas of research into the probable cause of keratoconus is the role of oxidative stress3
There needs to exist a balance between degradative enzymes, and the inhibitor enzymes (those that reduce their actions) and the level of environmental stress that the cornea suffers, this is called homeostasis.
If we have an eye degenerative condition this is due to multiple factors, therefore it is hard to isolate one cause and find one solution.
Want to know more? read the post: keratoconus overview.
Good Luck!
Heriberto R.
[1] Cristina Kenney M, Brown, Donald J “The cascade hypothesis of keratoconus,” Contact lens & anterior eye: the journal of the British Contact Lens Association 2003 Sep;26(3):139-46.
[2] Sies H, Jones DP. In: Fink G, ed. Encyclopedia of Stress. 2nd ed. Academic Press, 2007:45–48.
[3] Kenney, M.C.; Chwa, M.; Atilano, S.R.; Tran, A.; Carballo, M.; Saghizadeh, M.; Vasiliou, V.;
Adachi, W.; Brown, D.J. Increased levels of catalase and cathepsin V/L2 but decreased TIMP-1 in keratoconus corneas: evidence that oxidative stress plays a role in this disorder. Investig. Ophthalmol. Vis. Sci. 2005, 46, 823–832.
[4] Current eye research 2010 Mar;35(3):185-91 Are proteinases the reason for keratoconus? Balasubramanian SA, Pye DC, Willcox MD.
Author Information: School of Optometry and Vision Science, The University of New South Wales, Sydney, NSW, Australia.
[5] Clinical and Experimental Optometry 2013 Mar;96(2):214-218
Effects of eye rubbing on the levels of protease, protease activity and cytokines in tears: relevance to keratoconus.Balasubramanian SA, Pye DC, Willcox MD. Author information: Brien Holden Vision Institute, Kensington, New South Wales, Australia.
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