Do dilated pupils affect your nighttime vision through prescription glasses?
Dan asked:
When I view the night sky through my glasses, (not using a telescope) stars lose their sharpness. Do I need a stronger prescription for night time viewing for when my eyes are fully dilated? My corrected daytime vision is great, so any advise? Thanks!
I know that dilated pupils let more light in. But my understanding of the eyeball is that more focal aberrations are introduced when your eye is dilated. The more lens/cornea, etc… surface area that is used, the stronger the correction factor (?) needs to be increased. So wouldn’t you need a different prescription to take these aberrations into account?
When I view the night sky through my glasses, (not using a telescope) stars lose their sharpness. Do I need a stronger prescription for night time viewing for when my eyes are fully dilated? My corrected daytime vision is great, so any advise? Thanks!
I know that dilated pupils let more light in. But my understanding of the eyeball is that more focal aberrations are introduced when your eye is dilated. The more lens/cornea, etc… surface area that is used, the stronger the correction factor (?) needs to be increased. So wouldn’t you need a different prescription to take these aberrations into account?
November 17th, 2009 at 10:01 am |
dilated pupils don’t affect ure nighttime vision. its just a way for your eye to get as much light in so u can see better. night time vision is always worse than daytime. u could try a stronger prescription if u wanted
November 20th, 2009 at 11:45 am |
Yes, a higher Rx may be necessary for night time. Usually though, most people don’t notice this effect unless they are wearing contact lenses which obviously sit right on the eye and have a smaller “Rx zone”.
You may also have an unusual cornea shape which makes light go into your eye at funny angle when your eyes are dilated. If your eye doctor has it available, you may ask for a corneal topography test. It basically takes a picture of the surface of your eye and looks like an “elevations” map of the world.
November 20th, 2009 at 5:18 pm |
Basic answer, Yes.
But it’s not as simple as that…
Several possible effects can take place when the pupils dilate at night.
1) if the glasses are a little (or a lot) out of date, the amount of blur produced by the error is dependent on the size of the pupil. So what may seem adequate glasses in the day-time may reveal their inadequacy at night.
2) The larger pupil may introduce into the optical system portions of the cornea with a different refration or abberation. This is fairly rare and not usually very significant, but it can be most marked, for example with early cataract.
2) Many people, some more than others, actually shift more short-sighted at night “night myopia”. It can sometimes be demonstrated with binoculars: set them for good distance focus in the daytime, and then see if, at night, the focus wheel has to be turned appreciably to get best distance vision.
Rarely, night driving glasses with an extra strength component can be useful. More often the hoped for effect is not achieved, or it turns out that the basic glasses were in fact slightly underpowered in the first place.