My 5 year old son is using specs since past 1n half years. My prob is every ophthalmologist tells a different power for his eyes. That too just within a period of 15 dayz. As such how can I ensure that the specs he ia using is of correct power. Sm drs say he has no spherical power prob. Only cylindrical variation is thr. Others say mild spherical power is also thr. Wat shd b believed. N y is there so mch variation causing confusion.