The American Optometric Association suggests that children should have their first regular eye exam at six months of age. Another vision exam should take place when a child is around two or three years of age when their vision undergoes its most rapid development and vision correction is most effective.
The ISNUMBER function is a quick, easy way to check if a cell contains a number. Our example used the IF function to illustrate how ISNUMBER can be used. If you haven't used IF in a formula before, you can read our lesson on the IF function here.
If the range might contain a blank cell, you should use the ISBLANK function to test for a zero value, as in the following example: Note that the above formula returns zero if there is a zero value in the cell, blank if the cell is blank, and other if anything else is in the cell.f you are checking a cell for a zero value and the cell is blank, the test evaluates to true. For example, if you have the following formula in cell A1.