The earlier concept that the normal range of eye pressure is from 10 to 20mm Hg has been discarded. A pressure as high as 27-28 mmHg may not be termed glaucoma. Other findings such as field changes and characteristic disc findings seen in glaucoma are taken into account to diagnose glaucoma. Even at normal pressures, optic nerve damage may occur a condition called normal tension glaucoma. So, you can say that there is such accepted eye pressure. I hope that helps.
Follow-up questions, if any, are welcome.
Please, click the ACCEPT BUTTON so that I can get my dues. BONUS and a POSITIVE FEEDBACK will be appreciated.