When is a person termed legally blind?

Q: My 25-year-old friend has an eye power of -7.00. Is it worse than -2.25? What is the eye power for one to be termed legally blind?

A:Your friend is suffering from myopia. Lower power of myopia is “better” than higher power. Legal blindness does not refer to the prescription of glasses, but is determined by Sneller acuity (number of lines read on the testing chart) and by field of vision.