It’s hard to give pointed answers to a question with such indefinite edges. There isn’t a firm demarcation line between clear lens and cataract because a cataract is always a clear lens that’s becoming cloudy. And that process takes time. Usually a great deal of time.
Cataracts Develop at a Very Slow Pace
There is a similarity between the awareness of getting cataracts and the awareness of growing taller between age 1 and 18. There’s never a day you think, “Well I’ll be, I’m taller than I was yesterday.” Yet still, imperceptibly and inexorably you grow taller as the years pass. It’s not until enough time passes that you can look back (now from a greater height) and think, “I’ve grown taller.”
The difference with cataracts and growing taller is that cataracts happen even slower. And because there is no outside gauge like a measuring tape to see the difference, the slow increase in blur over the years can feel normal. Or it can feel like it hasn’t happened at all. There isn’t a day where the vision is worse than the previous day. The only clue many of us get that something has changed is that a visual task that once was easy has become difficult, and we don’t know when that happened.
The nature of cataracts is always the same. It always involves the clear crystalline proteins that comprise your lens become cloudy. There is a compression of lens over time, wrought by new layers being added each year like the rings of a tree. So the density of the lens, and the change in clarity of its previously clear components, starts to let less light through.
2 Visual Symptoms of Cataracts
That change in density and clarity, the central feature of cataract formation, causes two specific visual symptoms. The increase in density starts to filter more of the light coming into your eyes. It is like turning down a volume knob on the amount of visual information that is able to make it to your retina. The change in clarity, on the other hand, starts to scatter the light coming into your eyes. This is usually described as glare. If you’ve ever had salt on your windshield and been blinded when sunlight hits it, you’ve seen firsthand how visually significant light scatter can be.
These two symptoms — increased filtering and scattering of light — are usually the key to discovering you’ve got cataracts. For light filtering, reading is usually the first and hardest hit. If you’ve ever thought, “I can read okay, I just need a lot more light than I used to,” the reason is usually a cataract. The other scenario is that you can drive without difficulty during the day, but it’s hard to drive at night because of the glare. Again, the reason is usually a cataract. You need a reading lamp to turn up the volume on the light that is getting filtered out by a cataract. And you hate oncoming headlights because of the increased light scatter from a cataract.
It’s hard to give any measurable absolute in the real world — outside the walls of an eye clinic — that says, “Now I know I’ve got cataracts.” It’s a few specific tasks that you begin to realize you can’t do as well as you’d like because of your vision that give those clues. When you got taller, there was some point in time you could grab a book on the top shelf that was once out of reach. You may or may not have thought about the years of growth it took to make that possible. If you take that book off the shelf now, and notice you can’t read it without a good reading light, you probably won’t consider the years of change it took for that problem to arise. But imperceptible as the change may be, you may have reached a new milestone. Whether or not you ever had the thought, “I’ve grown taller,” the change in vision over the years may lead you to think for the first time, “I’ve got cataracts.” The good news is, once you know, you don’t need to have them for long and may be able to get better vision than ever.