when a patient comes into the clinic and their main symptom is blurry night
vision one of the first possibilities that comes to my head that might cause
that is astigmatism why does astigmatism cause extra blurry nighttime vision and
I'm going to show you something that you can do right now on your phone
or your computer to determine if you might have astigmatism let's focus in
now the main refractive areas that most people have are nearsightedness farsightedness and
astigmatism with astigmatism being the worst word ever it sounds like a serious disease
and it's usually the word that everybody remembers after they go to the eye doctor
you have astigmatism when one part of your eye is more curved than the other part of
the eye in fact you'll hear doctors using the analogy still that hey your eye is shaped like
a football and not a basketball your eye isn't perfectly round it's not perfectly spherical
and this usually happens in either the cornea with corneal astigmatism or in the crystalline
lens with lenticular astigmatism now because you have this Bend in your eye your eyes bend light
weird and it doesn't Focus to a single point in fact the word astigmatism means without point
or without spot meaning your eye doesn't Focus to a nice single Focus Point instead it has a
stretched focal point so because of this stretched focal point people will notice that their vision
and is stretched out as well especially lights when they look at lights maybe a round light
might be shaped like an oval or have streaks or glare lights coming out of there also they'll
look at letters maybe black letters on a white background and notice that there's a shadow or
a backdrop or a stretched appearance coming off of that letter as well it'll also cause
the eye to not focus very well it'll constantly be trying to refocus finding the best Clarity in
that stretched focal point this will cause the guys to strain out get tired be blurry and so
sometimes will cause headaches so why in the world is astigmatism worse at night time at night time
our pupils need to dilate to let more light in the pupils will get bigger and it'll also catch
more of that curve that bend in the eye and so you'll have more of those peripheral light rays
coming in from the side that get bent weird and cause that focal stretch point to stretch out
even farther and that's why people notice this the blur and the symptoms worse at nighttime
because their pupils are bigger catching more of that bent cornea or lens so a lot of times I'll
hear when people are driving they'll notice that lights headlights street lights maybe Christmas
lights during Christmas time will be stretched out they'll have streaks coming out of it more
glare or Halo patterns coming off of it and their vision is just extra blurry and so that's why when
I hear that my first thought or one of my first thoughts is astigmatism now obviously astigmatism
isn't the only thing that can cause all those symptoms so it's definitely best to get an eye
exam if you are having these symptoms to make sure that it's astigmatism and if it is astigmatism
you can get it corrected with glasses or contact lenses and on the flip side when pupils constrict
and get smaller in bright light then people might have Clear Vision they'll have less light streaks
less blur and this is mainly because that pupil is blocking out that peripheral light rays that
need to be bent kind of weird it's just getting those Central rays and this is also why squinting
can help people with astigmatism is when they squint really bad it's almost like constricting
the pupil or they're blocking those peripheral light rays to help them see better and focus
better it's cutting down those weird bent light rays from the curve in the eye now if you have
some of these symptoms and you're curious if you have astigmatism one at home test that's
been around for a long time is called the dial test the astigmatism dial test I'll put a link
to this in the description but also put it on the screen as I'm describing how it works and we'll do
this right now so if you have it on your computer screen look at the computer or if you have it on
your phone hold it about 12 to 16 inches kind of like if you're looking to read a book or looking
at your text and what you're going to do is you're going to test one eye at a time so cover one eye
using the open eye look in the middle of this dial and if you notice any of those lines are darker
Bolder crisper clearer and then some other lines are maybe more grayed out or fuzzy not as crisp
on the edges then you could have astigmatism and then be sure to test the other eye as well
so if you wear glasses and you're not sure if you have astigmatism see if you can find your
prescription and if you find the sphere cylinder axis sphere is nearsighted and farsightedness
cylinder is your astigmatism amount an axis is where your curve is for your astigmatism
if by doing this you just found out that you have astigmatism let me know in the comments
if you want to learn more about astigmatism I go into more detail here in this video and
definitely check out my other videos right here I'm Dr. Neal Guymon, Dr. EyeGuy, stay focused