Deserts are known for their harsh conditions. These all stress the eye, leading to the development of cataracts. Heat and sunlight are the major factors, but others such as malnutrition and dehydration also have an affect.
Causes
The lens of the eye is, at its healthiest, clear.
It's made of various proteins that can be damaged and broken by heat. Due to this, the lens becomes cloudy, leading to cataract formation.
The hotter an area is, both by strength and by duration, the more likely the heat is to instigate cataracts. Considering deserts are hot, no wonder cataracts are more prevalent in deserts.
Intense sunlight puts the eye under oxidative stress, a process whereby oxygen-containing unstable molecules called ROS damage cells (and hence tissues at a wider scale).
ROS is produced as part of cellular metabolism; exposure to light also produces them. Light penetrates the eye to cause this damage, even more so when it's UV.
As deserts have a lot of intense sunlight, especially UV rays, of course deserts accelerate cararact formation.
Contributing Factors
Malnutrition and dehydration contribute to cataract formation rather than directly causing the condition. However, as they are significant contributions (plus they are significant desert problems), their acknowledgement is relevant.
The eye's lens requires specific vitamins (most famously vitamin C) to be healthy.
Malnutrition leads to deficiencies in all minerals and vitamins, including those necessary for the lens' health. An unhealthy eye leads to cataracts.
As it's easy to suffer malnutrition in a desert, it's thus easy to suffer cataract development in deserts, too.
Dehydration doesn't cause cataracts directly.
Rather, they make the eye dry, leading to inflammation which, over time, can damage the lens and hence results in cataracts. Also, a hydrated eye means the lens is clear and functional: ultimately, this means cataracts-free.
Deserts are pretty easy to dehydrate in so this is another explanation of desert cataracts.
There's another contributing factor that's only relevant to some desert-dwellers: Arabs. This ethnic group, including individuals who don't reside in a desert, have a higher genetic susceptibility to developing cataracts than other ethnic groups. This shall be explored in a seperate post.
Conclusion
Therefore, it's quite clear that common issues in deserts happen to allign with common causes of (and contributions towards) cataracts. It thus can't be surprising that cataracts are prevalent in deserts.
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