20/15

 

I had my last follow-up at Lasik MD and everything is fantastic. I continue to marvel at how profound the change is. In the evening, I keep having the thought ‘Remember to take your contact lenses out’, it is such a weird (and great) feeling.

While in the Doctor’s office, they made sure the corneas are fine and did the standard eye test. Over the last month, I had moved from 20/20 to 20/15 – which is better. But I realized, I do not know why it is better? In fact, I really don’t know what this whole measurement system is all about, so I looked it up:

In the term "20/20 vision", the numerator refers to the distance in feet between the subject and the chart. The denominator indicates the size of the letters, specifically it denotes the separation at which the lines that make up those letters would be separated by a visual angle of 1 arc minute, which for the lowest line that is read by an eye with no refractive error (or the errors corrected) is usually 20 feet.

More:

If a person has a visual acuity of 20/40, he is said to see detail from 20 feet away the same as a person with normal eyesight would see it from 40 feet away. It is possible to have vision superior to 20/20: the maximum acuity of the human eye without visual aids (such as binoculars) is generally thought to be around 20/10 (6/3) however, recent test subjects have exceeded 20/8 vision.[6] Some birds of prey, such as hawks, are believed to have an acuity of around 20/2;[7] in this respect, their vision is much better than human eyesight. This helps them hunt more efficiently.

Using this logic, I probably started at 20/140. So at 20/15, I am somewhere between a normal person and a hawk. Amazing.

Via.

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