eye sight query?

Question

Does anybody suffer from superb eyesight at night or when it is cloudy and dark however during normal daylight (particulary sunny days) the ability to see clearly and with sharp detail dimishes. road signs are particularly awkward and number plates. get vague explanations from opticicians, milky vitreous, opaque lenses, cataracts, all seem to have a different explanation. I'm in my 40's not a pensioner.

Answer 1

You might have cone dystrophy, a genetic disorder characterized by loss of the cone cells from the eye. Cone cells are normally responsible for color vision, as well as visual acuity in well-lit conditions. Thus, their selective dysfunction would make it possible for the rod cells in your eyes to be adequate, thereby allowing excellent low-light, night vision, but also account for poorer eyesight during the day.

Answer 2

Well, depth of field is normally affected by the size of the aperture and this can affect the quality of the image.

At night, your iris (the aperture to your eye) is wide open (to capture most light) and during the day it will be smaller to restrict the amount of light entering your eye.

Your symptom is strange, because normally, the smaller the aperture, the better the image. If you hold both hands up and press your thumbs and forefingers together to form a very small hole and then look through it with one eye, what you see should be sharper, more in focus and clearer than normal.

I've seen 'pinhole spectacles' advertised that are supposed to work in this fashion instead of normal or variable spectacles - don't know anyone who has a pair though.

As you are in your 40's, it is likely that you just have the normal deterioration of your eyesight beginning (it normally starts around then).

Our eyes interpret the different wavelengths of light as spacial frequencies on our retinas. The higher the spacial frequency, the finer the detail we can pick up with our eyes. The upper frequency limit (the cut off frequency) is dictated by the diameter of the lens in your eye. It may well be that with age, your lenses are becoming less flexible, distorting the incoming light, particularly noticeable at the high frequencies.

It is most probable, that at night, you just can't see these high frequency wavelengths as they are missing from the light spectrum (no sun) - so your brain convinces you that the image is better.

Answer 3

You should ask your GP to refer you to a Consultant at a reputable Hospital Eye Department. Nothing against opticians but they aren't the best qualified to deal with the kind of phenomena you describe