Any opticians around? Don't understand contact lens prescription....

[fluffyhamster]

DS (16) had an eye test for his contact lenses as the right one seemed to have changed. He has astigmatism in this eye.

His prescription was previously:
BC 8.5
DIA 14.3
+0.50
Cyl/Axis -0.75 180

He's been given a print out of his new prescription in a different format and I can't work out what's going on:

8.50/14.50 +0.00/-0.75 x 10

Surely this means that this is now 0.00 power in the lens, so why bother?
Also, what is the significance of the axis going from 180 to 10?

I can call the optician tomorrow, but I was hoping to order him some new contacts asap.
He says he remembers the optician saying something about him having "pilot's vision" but he can't remember anything else .

the first number is the curvature of the lens 8.5 in your case
second is the diameter of the lens (14.5)

next you have the prescription
0.00 means no basic long or short sightedness
-0.75 is the amount of astigmatism
10 is the direction along which the astigmatism lies

if you think of a protractor ...half moon with 0-180 degrees marked on it then it's the same for astigmatism so really 10 and 180 are basically horizontal so no big change there

TBH it's not a large prescription that would scream "give this patient lenses" to me but some folks just do not like their specs.

the difference between the two is probably down to a different type of lens and how that interacts and fits on the eye can alter the prescription of the lens, without there being much, if any change in your son's actual prescription

...pretty much how you might be a 12 dress in one shop and a 10 in the other iyswim

Thank you! That's REALLY helpful.

They're not recommending a different brand of lens, so does that mean my son's eyesight has changed slightly?
Why bother if there is no 'power' in it? Does the shape of a toric lens in some way improve his vision?

He has a much bigger prescription in his left eye (-2.25) and says he prefers wearing lenses in both eyes - does that make sense?

I don't wear contacts, so it's all a bit of a mystery to me!

It's not a massive prescription, but I suspect he's actually a bit higher in the astigmatic bit of his prescription in his spectacle prescription. So the cyl/axis will make more difference.

However, it is very difficult to get an accurate reading for a contact lens prescription unless patients actually come in wearing their lenses (massive bugbear of mine), especially for torics (lenses for astigmatism).

it is a small prescription, but if the patient likes it then it makes sense to see as well as possible and have even that small amount of astigmatism corrected, some are happy to wander around in soft focus, others are not

Also, prescriptions can be written in two ways....with the astigmatism as plus or minus
you can measure the whole power of the eye, and work out how much less to give to correct any specific astigmatism along the axis (minus cyl)
or
you work out the power of the eye up to the level of the astigmatism and then any extra to get to the whole prescription (plus cyl)

soooooo, if any of this is making sense, if we take your prescription

0.00/-0.75x 10 this seems like a nothing prescription but it is exactly the same as -0.75/+0.75x100
it makes no difference if the prescription is written in + or - cyl, it's just numbers that give the same result although contact lens prescriptions tend to be in minus cyl.

tbh if both eyes had that type of correction then he'd probably not bother with specs (unless he was feeling a distance blur or maybe struggling with close/computer with the astigmatism,) however since his other eye is much bigger power wise he will be aware of the distance blur and will be keen to keep both eyes up to best acuity.

OK, thanks again. Sound like we should just get one box and see how he gets on then.

Really appreciate the late night consultation and help

My eye glass prescription is -100 -100 x 100 right eye
-150 left eye what is the prescription for contacts such as the power cycl axis