Astigmatism may be related to low Vitamin D

Astigmatism Patient Info
"Astigmatism can run in families and seems to be more common in premature or low-birth-weight babies."
Note that diseases running in families are often related to low vitamin D
Note that premature births are also related to low vitamin D
The Prevalence of Astigmatism and its Determinants in a Rural Population of Iran April 2014
Astigmatism BMJ
Astigmatism in twin infants is related to pregnant nutrition before 2014 full text online
"Moreover, animal study indicated that refraction error was induced by insufficiency of vitamine D and calcium in young birds"
"For factors associated with the infants, umbilical vein serum levels of calcium and vitamins D, and birth weight were associated with increased risk of astigmatism (Table 2)"
"If maternal nutrients such as magnesium, vitamin A and D during pregnancy are insufficient, fetal cornea development will be disrupted, decreasing the function of anti-traction"
Note: Twins have lower levels of vitamin D
Seeing the Light: Why Sun Exposure May Be Good for Your Eyes MarksDialyApple June 2011
42% of Americans aged 12-54 now suffer from myopia. Was 25% in the early 1970s."
Vitamin D Deficiency & Blurred Vision June 2015