High Intraocular Pressure

My intraocular pressure is a little higher than average and my doctor- he is specialist of glaucoma- advise me to apply eye lotion to prevent from glaucoma, but recently I've have some doubts about his way because there seem not to be found a clear cause of glaucoma . Now I'm thinking that high Intraocular Pressure is not a cause of glaucoma if it's not Primary Open Angle Glaucoma (POAG). The total size of the eye ball is quite larger than that of the cornea and because of the aqueous humour isn't filled within the eyeball and it's filled only around the cornea, the  pressure on the retina and the optic nerve is quite lower than intraocular pressure which is messured on the cornea. The pressure is dependent on the surface area. I estimate the ratio is a 15:1 roughly; but I don't know how accurate is this estimation because I'm not a specialist. And from my result, real pressure which means pressure on the retina and optic nerve is about 1/15 of measured Intraocular Pressure. In my country In case of POAG, It seems to be  quite effective if intraocular pressure drop 30%, and I heard that 90% of POAG is NTG. Actually my average intraocular pressure is around 21mmHg. And let us suppose I get NTG and I succeed to drop 30% of my Intraocular Pressure. Now by using my estimation, the 30% is 0.34mmHg (21mmHg×30%×1/15 = 0.42mmHg) as the pressure on the retina and optic nerve. 0.42mmHg is about 0.5g/cm. Actually is this adequately for me? Why can a little pressure be effective on NTG?

[John C Hagan III, MD, FACS, FAAO]

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JCH MD