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.
The CELL function returns information about the formatting, location, or contents of a cell. For example, if you want to verify that a cell contains a numeric value instead of text before you perform a calculation on it, you can use the following formula: = IF(CELL(type, A1) = v, A1 * 2, 0).