My husband and I recently became proud first time grandparents to a beautiful baby boy. Naturally, all of our grandson’s first degree relatives want to lay claim to the genes that have contributed to the baby’s adorableness, but it’s obvious that the baby is a carbon copy of my son in law. After ensuring that the baby was healthy, the next obvious question was “what color eyes does he have?” His eyes are a striking shade of blue, much like those of a Siberian husky. His dad’s eyes are brown, his mom’s are green. Three of his grandparents have varying shades of blue and the other grandparent is brown eyed.
The genetics of eye color are more complicated than the Mendelian genetics most of us learned in basic bioLott and that of course answers the question of how two brown eyed parents can have a blue eyed child. But back to my grandson… Will his eyes stay blue? The short answer is we don’t know yet.
A study out of the Byers Eye Institute at Stanford tracked 148 babies in California – ⅔ with brown eyes and ⅕ with blue. Two years later, 73 of the 77 brown eyed babies stayed brown, and of the 40 blue eyed babies,11 changed to brown, 3 to hazel, and 2 to green; the rest stayed blue eyed. It’s still a mystery as to what causes eyes to change color, and another study actually showed that sometimes a normal shift in eye color can happen up to the age of 6. If eyes change color in adulthood, such as in the late singer David Bowie, think of injury or infection as the cause. Either way, our family is excited and grateful for our new little addition no matter what his eye color is.
Can too much coffee cause glaucoma? Yes, no, and maybe. A recent study published in the June edition of Ophthalmology determined that consuming large amounts of caffeine daily increased the risk of glaucoma by more than three fold for those with a genetic predisposition for higher eye pressure. Glaucoma is the leading cause of blindness in the United States and often goes undetected for years since it’s first impact is on peripheral vision. Although many factors contribute to glaucoma, high intraocular pressure is an important risk factor in the disease as well as being the primary target of glaucoma drops whose goal is to decrease elevated eye pressure. Researchers studied the relationship between caffeine, eye pressure and patients who had glaucoma, and concluded that caffeine intake was not associated with causing glaucoma or high eye pressure overall, BUT, in patients with a high genetic predisposition to elevated eye pressure, greater caffeine consumption was associated with higher eye pressure and higher prevalence of glaucoma. So how much caffeine are we talking about? The study determined that patients who consumed more than 321 mg of caffeine (about 3 cups) were at risk for high eye pressure and glaucoma, but again, only if they were in that high genetic risk category.
Park Eye Center 