Submitted by cle_eech t3_xygyty in askscience
Apologies if this has been answered already. My vision is good for my age, but it is much harder to read menus etc. in dimly lit rooms. I find myself tapping on my iPhone flashlight or holding a menu closer to a candle. Much like I saw my father and other adults do when I was a kid,
Could be cataracts. The lens on your eye (s) becomes cloudy and can cause a number of different symptoms including your night vision becoming worse. My optometrist said mine were getting worse last exam and will most likely need surgery after my next exam. It's a simple surgery from what I've heard and read.
https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/cataracts
Your eye is like a camera. To achieve focus on any camera, you have 3 options. Option 1 is what a healthy eye normally does, which is to focus your lens to a distance of an object you wish to capture.
But as you age, the lens in your eye loses elasticity and it's harder to change the distance to which it is focused. In fact, this function is the first thing to go for most people - the lens' ability to stretch and compress into a desired shape is progressively lost, which is why reading becomes harder.
This is like switching to a camera with a fixed lens, and is a main reason why surgery can't fix the loss of ability to see up close.
But if the lens becomes fixed to a narrower set of depths, you can still use options 2 and 3.
Option 2 is to increase the distance between the camera and the object to the one that your lens is already focused at. You've seen people do this (or may have done it yourself) when you moved the thing you're reading further away.
The last thing you can do is to increase the range of depths that your fixed lens is focused on. This is done by making a tighter aperture, which reduces light scatter*, thereby increasing the depth of field.
Your eye can control this in two ways. You can squint to tighten your aperture, or you can force your pupils to reduce in size by shining more light onto an object.
As you age, you can expect to be insinctively doing an increasing combination of all three modes of fixed-lens focusing. This is why those of us over the age of 40 buy reading glasses by the dozen - this is akin to carrying an extra fixed camera lens set to a closer focal distance.
*Not the most correct explanation for why the DOF is increased. It actually has more to do with ray angles, but it's close enough for the sake of this explanation.
It's a whole host of different issues. As we age, the lens gets yellow, the pupil can't open as far, and the number of light-sensing cones decreases.
https://www.ncbi.nlm.nih.gov/books/NBK218971/
As for yellowing, "At age 60, the amount of light reaching the photoreceptor cells of the retina is only one-third of the amount seen at age 20. "
https://www.2020mag.com/article/color-changes-as-the-eyes-age
...or better...
https://www.lrc.rpi.edu/programs/lightHealth/AARP/healthcare/lightingOlderAdults/agingeye.asp
There are several mechanisms that can impact the transmission of light through the various layers of the eye, but in general as we age the transmission of the eye will decrease significantly and intraocular scatter will increase due to "yellowing or clouding" of the various layers.
In fact the IES (Illumination Engineering Society) which publishes recommended light levels for various applications (indoor and outdoor) will generally recommend much higher light levels (sometimes as much as 2X) for spaces that are used by predominantly by elderly people (nursing home for example) to accommodate for the loss in transmission we experience as we age.
As long as you have had your eyes examined and there isn't anything abnormal causing the transmission loss, it's just something to be expected as we age.
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Cataract surgery is simple for the patient but a delicate operation for the surgeon. Nevertheless, the success rate is remarkably high. The success rate is even higher if carried out early; as with many operations, the risk increases with age.
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I have optic neuritis causes by having very poor vision. I also get retina tears from straining to see. I am only 32 and have not been able to see in dim lighting for about 7 years. Colors are no longer as bright as they used to be. I imagine by the time I'm 60 my vision will probably not be corrected with glasses or contacts. Just as our joints and skin the eyes take a decline in over all health as well.
[deleted] t1_irh8df2 wrote
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