Measuring Your Level of Vision

One area of the sight test that’s always misunderstood by the patient is in regard to explaining whether or not your eyesight has got higher or worse and does that imply the eyeglasses want changing?

There are two related, but very distinct ways to talk about and describe your eyesight. One is to talk about what your prescription is and how it has changed. The opposite is to talk about what line you’ll be able to see on the sight test chart. The 2 are linked, however a change in a single doesn’t essentially mean a change in the other. I often say to my patients “It would not matter what prescription is in your specs as lengthy you can see the chart. It is when you possibly can’t see the chart, despite what we put in your eyeglasses, that now we have a problem.”

The chart usually used is a called a Snellen chart. It’s named after a Dutch eye doctor called Hermann Snellen who designed it in 1862. The letters are large at the top and get gradually smaller as you move down the chart. The thickness of the lines that make up the letters, is the same as the thickness of the spaces between the lines. The height and width of the letters is 5 occasions the width of the lines.

You will have heard the phrase “20/20”. This is often understood to mean perfect vision. Actually, most people with good vision have eyesight better than 20/20. It means which you could see, from 20 feet, what you need to be able to see from 20 feet. We now truly use 6/6 instead of 20/20. This represents the change from toes to meters (20 ft equals 6 meters). If you happen to can see 6/5(very good eyesight), this means you’ll be able to see, from 6 meters, what you need to need to get to 5 meters to be able to see. In case you have 6/60 (poor eyesight), it means you must be 6 meters away to see what you should be able to see from 60 meters. There are completely different levels in between.

The primary measure is called vision. This is a measure of what you can see without any help at all. For someone who does not want glasses and has no eye health problems, it is often 6/6 or a little better. As your prescription gets stronger, the second number gets higher. The top letter of the chart is often 6/60. Needing eyeglasses is just not the only cause for this number to be higher. When you have eye problems, chances are you’ll not have a prescription but still only be able to see the bigger letters. This is the place the time period visual acuity turns into important.

Your visual acuity tells us how well you’ll be able to see with the right prescription in your glasses. When you’ve got something wrong with your eyes akin to cataract or macular degeneration, then even with the absolute best pair of specs for you, it’s possible you’ll only see among the bigger letters on the chart. Precisely how far down the chart you possibly can see with the very best spectacles is your visual acuity.

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