Optician can see the start of a cataract

I think the answer is...."it depends".  Here's my story. I'm now 70. Starting in my early 60's during my annual check-ups, my optometrist would say, "I see the beginnings of a minor catract but you are a long way off from it being a problem or interefering with your vision". For almost a decade, every time i went back for my annual check, the optometrist would say the same thing and that it had hardly progressed at all. This included last year's check up in the Spring.  Then in the Summer, my vision suddenly started to get quite blurry over the course of several months. I went to an opthamologist and he said I needed cataract surgery. I had severe catracts and needed the surgery as sooon as possible. I successfully had both eyes done last Fall. 

After being perplexed by how fast, or why, it had progressed so fast after years of it essentially being dormant, I wanted some answers. After  some questioning and research, I found the answer.... my new boat. In the Spring of last year I had bought my first ever boat and was constantly out on the lake and in the bright sun, either working on the boat or riding in it..... WITHOUT EVER WEARING SUN GLASSES. Constant exposure of the eyes to direct sun light and its reflection off the water is horrible for cataracts. I didn't know. Now I know, but it's too late. In any event, I'm lucky. I came through both surgeries with only one minor complication, which eventually cleared up. If you protect your eysight from overexposure to bright sunlight, you can go years even decades with your cataract progressing little or not at all.

It varies drastically,  most often it takes many years for the cataract to noticeably impact vision from the time a doctor first identifies it, even decade(s). In other cases a cataract can develop rapidly. I had a problem cataract appear in an eye that went from best corrected vision of 20/25 to 20/60 within about 3.5 months, i.e. even with contacts/glasses that was the best that eye could see. My optometrist didn't even realize it was a cataract at first, due to my age and not thinking the trace changes she saw in the lens accounted for the decline in vision, but an opthalmologist eventually clearly diagnosed it. Since my other eye still had good vision I tuned it out for quite a while before surgery since my brain just used the good eye, and I was hoping to wait for better newer replacement lenses to be approved.

You are the one who decides when you "need treatment" based on when the cataract is impairing your vision enough that you wish to get surgery, which is usually partly based on whether insurance or government healthcare will pay for it. Usually healthcare plans cover cataract surgery when vision in an eye can't be corrected well enough to meet the requirements to drive,  which in the US usually means the eye can't be corrected to  20/40. However some places are starting to be more flexible about coverage since for instance cataracts can impair night vision and the ability to drive at night even before they make regular visual acuity worse than the driving standard. Some  will cover it once the cataract is having a problematic impact on vision for work or regular life activities as determined by an ophthalmologist, or consider visual tests related to night vision,  though most I think still  use the standard of covering it once vision is worse than whats required to drive. 

Each person is different. In my case, I had early stages of cataracts when I was in my 50's, then in 2013, I was again told that I had early stages of cataracts. I saw an eye doctor in January 2014, again I was told I had early stages of cataracts. By July 2014, I couldn't read a book, by November, I couldn't read a newspaper because everything was gray. By December, I couldn't see people faces. I thought I was going blind due to my diabetes. I thought I was going to have to learn braille that is how bad my vision got.

Finally got an appointment to see my eye doctor in January 2015, and she said I had very dense cataracts and I needed surgery soon. She said I would be contacted in 1 to 2 months. I didn't hear anything in 4 months, so I called agaim and was finally see by the cataract surgeon in July and had the surgery doneeds in August 2015. I can see without glasses at times, but I do wear glasses to see tiny print or to see far away like 2 to 3 blocks away in the US. But I usually use glasses when my double vision returns. I have always had Double vision, so this is not a new result of having cataracts.

So as I stated before, everyone is different. Mine came on gradually within a year. But I had other problems going on that year including being on haemodyalysis and having 4 amputations on my legs, so that may have been a factor why my vision went away so quickly