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.
A few pointers while using OR() 1  If any array or cell reference argument contain empty cells, those values will be ignored. 2  If the specified cell range contains no logical values, OR function returns the #Value! (its the error value)  To check whether a value occurs in an array, you can use OR array formula.