Do not take it for granted. I started wearing glasses at the age of eight. I have one of the worst cases of astigmatism my eye specialist has ever seen.
My sight without glasses is 20/400, which is considered legally blind.
About 14 years ago about six months after some major surgery I also developed a bad case of Iritis in my right eye (thankfully that is also the eye with the worst vision) Now I have had 6 rounds of the iritis in the 14 year period, and each time more and more damage can be done to my vision. I dread the feeling of waking up in the morning with the blurred vision and the red inflamed eye.
I can not use my right eye when taking photos, and though I prefer a screen view like on some cameras, my rebel does not have one. maybe someday I will be able to afford a newer one.
I just want to remind everyone not to neglect there eyesight, Get your eyes examined at least every two years (and I do not mean the eye chart in your physicians office)