Seeing Double: The Differences in Twins’ Vision

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It’s not your eyesight that has you seeing double, it is the ever increasing number of twins being born. Have you ever wondered about the similarities and differences in twins’ vision? Many factors can play into this including whether or not the twins are identical or fraternal, their environment, and quite simply their genetics.

Identical Twins: Identical twins are also known as monozygotic twins, meaning they were created of one egg that splits into two. While the DNA composition that makes up the identical twins is the same, it does change over time as they could be subjected to different environments.

One study, that has been the compilation of Dr. Mohamed Dirani’s life work, shows that an identical twin is 80% more likely to develop myopia if their twin has myopia, versus a 40% chance if you are not a twin. An interesting fact on identical twins is that their eyesight could vary simply on the environment which they interact with every day. Imagine one twin works inside while the other works outside. The visual strain they would likely develop is completely separate, but the underlying visual problem (i.e. myopia) would occur regardless of their environment.

Fraternal Twins: Fraternal twins, or dizygotic twins, are two separate eggs that are fertilized with two separate sperms. While fraternal twins share a stronger connection that most siblings of different ages, their DNA composition is as different as if they were born 4 years apart. This means that their vision could be drastically different, but family genetics can create similar visual impairments. If your parents are nearsighted, your chance of being nearsighted is much higher; however, this could be said of all siblings (non-twins).

Why is this important to know? It is fundamental in understanding how genetics and environment play into individual’s eyesight. Not to mention the chances of you being a twin, knowing a twin, or having a twin is about a 1 in 30 chance (as of 2009).

Famous Twins (how many did you know?):

  • Ashton and Michael Kutcher (fraternal)
  • Scarlett and Hunter Johannson (fraternal)
  • Kiefer and Rachel Sutherland (fraternal)
  • Vin and Paul Diesel (fraternal)
  • Gisele and Patricia Bundchen (fraternal)
  • Alanis and Wade Morisette (fraternal)
  • Aaron and Shawn Ashmore (identical)
  • Tia & Tamera Mowry (identical)
  • Mary-Kate & Ashley Olsen (fraternal)

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